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Sample records for seed dispersal mutualism

  1. An invasive slug exploits an ant-seed dispersal mutualism.

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    Meadley Dunphy, Shannon A; Prior, Kirsten M; Frederickson, Megan E

    2016-05-01

    Plant-animal mutualisms, such as seed dispersal, are often vulnerable to disruption by invasive species. Here, we show for the first time how a non-ant invasive species negatively affects seed dispersal by ants. We examined the effects of several animal species that co-occur in a temperate deciduous forest-including native and invasive seed-dispersing ants (Aphaenogaster rudis and Myrmica rubra, respectively), an invasive slug (Arion subfuscus), and native rodents-on a native myrmecochorous plant, Asarum canadense. We experimentally manipulated ant, slug, and rodent access to seed depots and measured seed removal. We also video-recorded depots to determine which other taxa interact with seeds. We found that A. rudis was the main disperser of seeds and that A. subfuscus consumed elaiosomes without dispersing seeds. Rodent visitation was rare, and rodent exclusion had no significant effect on seed or elaiosome removal. We then used data obtained from laboratory and field mesocosm experiments to determine how elaiosome robbing by A. subfuscus affects seed dispersal by A. rudis and M. rubra. We found that elaiosome robbing by slugs reduced seed dispersal by ants, especially in mesocosms with A. rudis, which picks up seeds more slowly than M. rubra. Taken together, our results show that elaiosome robbing by an invasive slug reduces seed dispersal by ants, suggesting that invasive slugs can have profound negative effects on seed dispersal mutualisms.

  2. The bonobo-dialium positive interactions: seed dispersal mutualism.

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    Beaune, David; Bretagnolle, François; Bollache, Loïc; Hohmann, Gottfried; Surbeck, Martin; Bourson, Chloé; Fruth, Barbara

    2013-04-01

    A positive interaction is any interaction between individuals of the same or different species (mutualism) that provides a benefit to both partners such as increased fitness. Here we focus on seed dispersal mutualism between an animal (bonobo, Pan paniscus) and a plant (velvet tamarind trees, Dialium spp.). In the LuiKotale rainforest southwest of Salonga National Park, Democratic Republic of Congo, seven species of the genus Dialium account for 29.3% of all trees. Dialium is thus the dominant genus in this forest. Dialium fruits make up a large proportion of the diet of a habituated bonobo community in this forest. During the 6 months of the fruiting season, more than half of the bonobos' feeding time is devoted to Dialium fruits. Furthermore, Dialium fruits contribute a considerable proportion of sugar and protein to bonobos' dietary intake, being among the richest fruits for these nutrients. Bonobos in turn ingest fruits with seeds that are disseminated in their feces (endozoochory) at considerable distances (average: 1.25 km after 24 hr of average transit time). Endozoochory through the gut causes loss of the cuticle protection and tegumentary dormancy, as well as an increase in size by water uptake. Thus, after gut passage, seeds are better able to germinate. We consider other primate species as a potential seed disperser and conclude that Dialium germination is dependent on passage through bonobo guts. This plant-animal interaction highlights positive effects between two major organisms of the Congo basin rainforest, and establishes the role of the bonobo as an efficient disperser of Dialium seeds. Periodicals, Inc. © 2013 Wiley Periodicals, Inc.

  3. Anomalous, extreme weather disrupts obligate seed dispersal mutualism: snow in a subtropical forest ecosystem.

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    Zhou, Youbing; Newman, Chris; Chen, Jin; Xie, Zongqiang; Macdonald, David W

    2013-09-01

    Ongoing global climate change is predicted to increase the frequency and magnitude of extreme weather events, impacting population dynamics and community structure. There is, however, a critical lack of case studies considering how climatic perturbations affect biotic interactions. Here, we document how an obligate seed dispersal mutualism was disrupted by a temporally anomalous and meteorologically extreme interlude of unseasonably frigid weather, with accompanying snowstorms, in subtropical China, during January-February 2008. Based on the analysis of 5892 fecal samples (representing six mammalian seed dispersers), this event caused a substantial disruption to the relative seed dispersal function for the raisin tree Hovenia dulcis from prestorm 6.29 (2006) and 11.47 (2007), down to 0.35 during the storm (2008). Crucially, this was due to impacts on mammalian seed dispersers and not due to a paucity of fruit, where 4.63 fruit per branch were available in January 2008, vs. 3.73 in 2006 and 3.58 in 2007. An induced dietary shift occurred among omnivorous carnivores during this event, from the consumption fruit to small mammals and birds, reducing their role in seed dispersal substantially. Induced range shift extinguished the functionality of herbivorous mammals completely, however, seed dispersal function was compensated in part by three omnivorous carnivores during poststorm years, and thus while the mutualism remained intact it was enacted by a narrower assemblage of species, rendering the system more vulnerable to extrinsic perturbations. The storm's extended effects also had anthropogenic corollaries - migrating ungulates becoming exposed to heightened levels of illegal hunting - causing long-term modification to the seed dispersal community and mutualism dynamics. Furthermore, degraded forests proved especially vulnerable to the storm's effects. Considering increasing climate variability and anthropogenic disturbance, the impacts of such massive, aberrant

  4. A strong conditional mutualism limits and enhances seed dispersal and germination of a tropical palm

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    Klinger, R.; Rejmanek, M.

    2010-01-01

    Seed predation and seed dispersal can have strong effects on early life history stages of plants. These processes have often been studied as individual effects, but the degree to which their relative importance co-varies with seed predator abundance and how this influences seed germination rates is poorly understood. Therefore, we used a combination of observations and field experiments to determine the degree to which germination rates of the palm Astrocaryum mexicanum varied with abundance of a small mammal seed predator/disperser, Heteromysdesmarestianus, in a lowland tropical forest. Patterns of abundance of the two species were strongly related; density of H. desmarestianus was low in sites with low density of A. mexicanum and vice versa. Rates of predation and dispersal of A. mexicanum seeds depended on abundance of H. desmarestianus; sites with high densities of H. desmarestianus had the highest rates of seed predation and lowest rates of seed germination, but a greater total number of seeds were dispersed and there was greater density of seedlings, saplings, and adults of A. mexicanum in these sites. When abundance of H. desmarestianus was experimentally reduced, rates of seed predation decreased, but so did dispersal of A. mexicanum seeds. Critically, rates of germination of dispersed seeds were 5 times greater than undispersed seeds. The results suggest that the relationship between A. mexicanum and H. desmarestianus is a conditional mutualism that results in a strong local effect on the abundance of each species. However, the magnitude and direction of these effects are determined by the relative strength of opposing, but related, mechanisms. A. mexicanum nuts provide H. desmarestianus with a critical food resource, and while seed predation on A. mexicanum nuts by H. desmarestianus is very intense, A. mexicanum ultimately benefits because of the relatively high germination rates of its seeds that are dispersed by H. desmarestianus. ?? The Author(s) 2010.

  5. Pollination and seed dispersal of Melocactus ernestii Vaupel subsp. ernestii (Cactaceae) by lizards: an example of double mutualism.

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    Gomes, V G N; Quirino, Z G M; Machado, I C

    2014-03-01

    Recent studies show that the mutualistic role of lizards as pollinators and seed dispersers has been underestimated, with several ecological factors promoting such plant-animal interactions, especially on oceanic islands. Our aim is to provide a quantitative assessment of pollination and seed dispersal mutualisms with lizards in continental xeric habitats. We carried out focal observations of natural populations of Melocactus ernestii (Cactaceae) in the Caatinga, a Brazilian semiarid ecosystem, in order to record the frequency of visits, kind of resource searched and behaviour of visiting animals towards flowers and/or fruits. We made a new record of the lizard Tropidurus semitaeniatus foraging on flowers and fruits of M. ernestii. During the search for nectar, T. semitaeniatus contacted the reproductive structures of the flowers and transported pollen attached to its snout. Nectar production started at 14:00 h, with an average volume of 24.4 μl and an average concentration of solutes of 33%. Approximately 80% of the seeds of M. ernestii found in the faeces of T. semitaeniatus germinated under natural conditions. The roles of T. semitaeniatus as pollinator and seed disperser for M. ernestii show a clear relationship of double mutualism between two endemic species, which may result from the environmental conditions to which both species are subject. Seasonality, low water availability and arthropod supply in the environment, high local lizard densities, continuous nectar production by the flower and fruits with juicy pulp may be influencing the visits and, consequently, pollination and seed dispersal by lizards in this cactus. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.

  6. Internal seed dispersal by parrots: an overview of a neglected mutualism

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    Guillermo Blanco

    2016-02-01

    Full Text Available Despite the fact that parrots (Psitacifformes are generalist apex frugivores, they have largely been considered plant antagonists and thus neglected as seed dispersers of their food plants. Internal dispersal was investigated by searching for seeds in faeces opportunistically collected at communal roosts, foraging sites and nests of eleven parrot species in different habitats and biomes in the Neotropics. Multiple intact seeds of seven plant species of five families were found in a variable proportion of faeces from four parrot species. The mean number of seeds of each plant species per dropping ranged between one and about sixty, with a maximum of almost five hundred seeds from the cacti Pilosocereus pachycladus in a single dropping of Lear’s Macaw (Anodorhynchus leari. All seeds retrieved were small (<3 mm and corresponded to herbs and relatively large, multiple-seeded fleshy berries and infrutescences from shrubs, trees and columnar cacti, often also dispersed by stomatochory. An overview of the potential constraints driving seed dispersal suggest that, despite the obvious size difference between seeds dispersed by endozoochory and stomatochory, there is no clear difference in fruit size depending on the dispersal mode. Regardless of the enhanced or limited germination capability after gut transit, a relatively large proportion of cacti seeds frequently found in the faeces of two parrot species were viable according to the tetrazolium test and germination experiments. The conservative results of our exploratory sampling and a literature review clearly indicate that the importance of parrots as endozoochorous dispersers has been largely under-appreciated due to the lack of research systematically searching for seeds in their faeces. We encourage the evaluation of seed dispersal and other mutualistic interactions mediated by parrots before their generalized population declines contribute to the collapse of key ecosystem processes.

  7. Fluff-thieving birds sabotage seed dispersal

    OpenAIRE

    Rohwer, Vanya G.; Pauw, Anton; Martin, Paul R.

    2017-01-01

    Characterizing many species interactions as mutualisms can be misleading because some members of the interaction derive greater fitness benefits at the expense of other members. We provide detailed natural history data on a suspected bird?plant mutualism in South Africa where many species of birds use fluffy Eriocephalus seed material to construct their nests, potentially dispersing seeds for the plant. We focus on a common bird, Prinia maculosa, which invests heavily in gathering Eriocephalu...

  8. Fluff-thieving birds sabotage seed dispersal.

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    Rohwer, Vanya G; Pauw, Anton; Martin, Paul R

    2017-01-01

    Characterizing many species interactions as mutualisms can be misleading because some members of the interaction derive greater fitness benefits at the expense of other members. We provide detailed natural history data on a suspected bird-plant mutualism in South Africa where many species of birds use fluffy Eriocephalus seed material to construct their nests, potentially dispersing seeds for the plant. We focus on a common bird, Prinia maculosa , which invests heavily in gathering Eriocephalus material. Prinias spent 5 of their median 6-day nest construction period adding seed material to their nests and frequently travelled outside their territory boundary to gather Eriocephalus material. Yet, prinias gathered primarily Eriocephalus fluff and actively avoided gathering seeds. The average prinia nest contained only 6.6 seeds, but contained fluff from 579 seeds. These data suggest that prinias provide limited dispersal benefits to Eriocephalus plants. By contrast, the large amounts of Eriocephalus fluff in prinia nests, and the effort that prinias invest in gathering it, suggest that prinias benefit from constructing their nests with Eriocephalus material. We end by outlining hypotheses for possible fitness benefits that Eriocephalus material could provide prinias and other birds.

  9. Fluff-thieving birds sabotage seed dispersal

    Science.gov (United States)

    2017-01-01

    Characterizing many species interactions as mutualisms can be misleading because some members of the interaction derive greater fitness benefits at the expense of other members. We provide detailed natural history data on a suspected bird–plant mutualism in South Africa where many species of birds use fluffy Eriocephalus seed material to construct their nests, potentially dispersing seeds for the plant. We focus on a common bird, Prinia maculosa, which invests heavily in gathering Eriocephalus material. Prinias spent 5 of their median 6-day nest construction period adding seed material to their nests and frequently travelled outside their territory boundary to gather Eriocephalus material. Yet, prinias gathered primarily Eriocephalus fluff and actively avoided gathering seeds. The average prinia nest contained only 6.6 seeds, but contained fluff from 579 seeds. These data suggest that prinias provide limited dispersal benefits to Eriocephalus plants. By contrast, the large amounts of Eriocephalus fluff in prinia nests, and the effort that prinias invest in gathering it, suggest that prinias benefit from constructing their nests with Eriocephalus material. We end by outlining hypotheses for possible fitness benefits that Eriocephalus material could provide prinias and other birds. PMID:28280552

  10. Signals can trump rewards in attracting seed-dispersing ants.

    Directory of Open Access Journals (Sweden)

    Kyle M Turner

    Full Text Available Both rewards and signals are important in mutualisms. In myrmecochory, or seed dispersal by ants, the benefits to plants are relatively well studied, but less is known about why ants pick up and move seeds. We examined seed dispersal by the ant Aphaenogaster rudis of four co-occurring species of plants, and tested whether morphology, chemical signaling, or the nutritional quality of fatty seed appendages called elaiosomes influenced dispersal rates. In removal trials, ants quickly collected diaspores (seeds plus elaiosomes of Asarum canadense, Trillium grandiflorum, and Sanguinaria canadensis, but largely neglected those of T. erectum. This discrepancy was not explained by differences in the bulk cost-benefit ratio, as assessed by the ratio of seed to elaiosome mass. We also provisioned colonies with diaspores from one of these four plant species or no diaspores as a control. Colonies performed best when fed S. canadensis diaspores, worst when fed T. grandiflorum, and intermediately when fed A. canadense, T. erectum, or no diaspores. Thus, the nutritional rewards in elaiosomes affected colony performance, but did not completely predict seed removal. Instead, high levels of oleic acid in T. grandiflorum elaiosomes may explain why ants disperse these diaspores even though they reduce ant colony performance. We show for the first time that different elaiosome-bearing plants provide rewards of different quality to ant colonies, but also that ants appear unable to accurately assess reward quality when encountering seeds. Instead, we suggest that signals can trump rewards as attractants of ants to seeds.

  11. Adaptive Advantage of Myrmecochory in the Ant-Dispersed Herb Lamium amplexicaule (Lamiaceae: Predation Avoidance through the Deterrence of Post-Dispersal Seed Predators.

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    Koki Tanaka

    Full Text Available Seed dispersal by ants (myrmecochory is found worldwide, but the benefits that plants obtain from this mutualism remain uncertain. In the present study, we conducted laboratory experiments to demonstrate seed predator avoidance as a benefit of myrmecochory using the annual ant-dispersed herb Lamium amplexicaule, the disperser ant Tetramorium tsushimae, and the seed predatory burrower bug Adomerus rotundus. We compared the predation intensity of Lamium amplexicaule seeds by Adomerus rotundus under the presence or absence of Tetramorium tsushimae. Both the number of seeds sucked by Adomerus rotundus adults and the feeding duration of sucked seeds by nymphs were significantly reduced in the presence of ants. This effect was most likely due to the behavioral alteration of Adomerus rotundus in response to the ant presence, because ants seldom predated Adomerus rotundus during the experiment. Our results demonstrated that the presence of ants decreases post-dispersal seed predation, even when the ants do not bury the seeds. The present study thus suggests that the non-consumptive effects of ants on seed predators benefit myrmecochorous plants.

  12. Harnessing ant defence at fruits reduces bruchid seed predation in a symbiotic ant–plant mutualism

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    Pringle, Elizabeth G.

    2014-01-01

    In horizontally transmitted mutualisms, mutualists disperse separately and reassemble in each generation with partners genetically unrelated to those in the previous generation. Because of this, there should be no selection on either partner to enhance the other's reproductive output directly. In symbiotic ant–plant mutualisms, myrmecophytic plants host defensive ant colonies, and ants defend the plants from herbivores. Plants and ants disperse separately, and, although ant defence can indirectly increase plant reproduction by reducing folivory, it is unclear whether ants can also directly increase plant reproduction by defending seeds. The neotropical tree Cordia alliodora hosts colonies of Azteca pittieri ants. The trees produce domatia where ants nest at stem nodes and also at the node between the peduncle and the rachides of the infloresence. Unlike the stem domatia, these reproductive domatia senesce after the tree fruits each year. In this study, I show that the tree's resident ant colony moves into these ephemeral reproductive domatia, where they tend honeydew-producing scale insects and patrol the nearby developing fruits. The presence of ants significantly reduced pre-dispersal seed predation by Amblycerus bruchid beetles, thereby directly increasing plant reproductive output. PMID:24807259

  13. Harnessing ant defence at fruits reduces bruchid seed predation in a symbiotic ant-plant mutualism.

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    Pringle, Elizabeth G

    2014-06-22

    In horizontally transmitted mutualisms, mutualists disperse separately and reassemble in each generation with partners genetically unrelated to those in the previous generation. Because of this, there should be no selection on either partner to enhance the other's reproductive output directly. In symbiotic ant-plant mutualisms, myrmecophytic plants host defensive ant colonies, and ants defend the plants from herbivores. Plants and ants disperse separately, and, although ant defence can indirectly increase plant reproduction by reducing folivory, it is unclear whether ants can also directly increase plant reproduction by defending seeds. The neotropical tree Cordia alliodora hosts colonies of Azteca pittieri ants. The trees produce domatia where ants nest at stem nodes and also at the node between the peduncle and the rachides of the infloresence. Unlike the stem domatia, these reproductive domatia senesce after the tree fruits each year. In this study, I show that the tree's resident ant colony moves into these ephemeral reproductive domatia, where they tend honeydew-producing scale insects and patrol the nearby developing fruits. The presence of ants significantly reduced pre-dispersal seed predation by Amblycerus bruchid beetles, thereby directly increasing plant reproductive output.

  14. Seed dispersal in fens

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    Middleton, B.; Van Diggelen, R.; Jensen, K.

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.

  15. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and

  16. Nest-mediated seed dispersal

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    Robert J. Warren; Jason P. Love; Mark A. Bradford

    2017-01-01

    Many plant seeds travel on the wind and through animal ingestion or adhesion; however, an overlooked dispersal mode may lurk within those dispersal modes. Viable seeds may remain attached or embedded within materials birds gather for nest building. Our objective was to determine if birds inadvertently transport seeds when they forage for plant materials to...

  17. Introducing cultivated trees into the wild: Wood pigeons as dispersers of domestic olive seeds

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    Perea, Ramón; Gutiérrez-Galán, Alejandro

    2016-02-01

    Animals may disperse cultivated trees outside the agricultural land, favoring the naturalization or, even, the invasiveness of domestic plants. However, the ecological and conservation implications of new or unexplored mutualisms between cultivated trees and wild animals are still far from clear. Here, we examine the possible role of an expanding and, locally, overabundant pigeon species (Columba palumbus) as an effective disperser of domestic olive trees (Olea europaea), a widespread cultivated tree, considered a naturalized and invasive species in many areas of the world. By analyzing crop and gizzard content we found that olive fruits were an important food item for pigeons in late winter and spring. A proportion of 40.3% pigeons consumed olive seeds, with an average consumption of 7.8 seeds per pigeon and day. Additionally, most seed sizes (up to 0.7 g) passed undamaged through the gut and were dispersed from cultivated olive orchards to areas covered by protected Mediterranean vegetation, recording minimal dispersal distances of 1.8-7.4 km. Greenhouse experiments showed that seeds dispersed by pigeons significantly favored the germination and establishment in comparison to non-ingested seeds. The ability of pigeons to effectively disperse domestic olive seeds may facilitate the introduction of cultivated olive trees into natural systems, including highly-protected wild olive woodlands. We recommend harvesting ornamental olive trees to reduce both pigeon overpopulation and the spread of artificially selected trees into the natural environment.

  18. Thieving rodents as substitute dispersers of megafaunal seeds

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    Jansen, Patrick A.; Hirsch, Ben T.; Emsens, Willem-Jan; Zamora-Gutierrez, Veronica; Wikelski, Martin; Kays, Roland

    2012-01-01

    The Neotropics have many plant species that seem to be adapted for seed dispersal by megafauna that went extinct in the late Pleistocene. Given the crucial importance of seed dispersal for plant persistence, it remains a mystery how these plants have survived more than 10,000 y without their mutualist dispersers. Here we present support for the hypothesis that secondary seed dispersal by scatter-hoarding rodents has facilitated the persistence of these large-seeded species. We used miniature radio transmitters to track the dispersal of reputedly megafaunal seeds by Central American agoutis, which scatter-hoard seeds in shallow caches in the soil throughout the forest. We found that seeds were initially cached at mostly short distances and then quickly dug up again. However, rather than eating the recovered seeds, agoutis continued to move and recache the seeds, up to 36 times. Agoutis dispersed an estimated 35% of seeds for >100 m. An estimated 14% of the cached seeds survived to the next year, when a new fruit crop became available to the rodents. Serial video-monitoring of cached seeds revealed that the stepwise dispersal was caused by agoutis repeatedly stealing and recaching each other’s buried seeds. Although previous studies suggest that rodents are poor dispersers, we demonstrate that communities of rodents can in fact provide highly effective long-distance seed dispersal. Our findings suggest that thieving scatter-hoarding rodents could substitute for extinct megafaunal seed dispersers of tropical large-seeded trees. PMID:22802644

  19. Frugivores bias seed-adult tree associations through nonrandom seed dispersal: a phylogenetic approach.

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    Razafindratsima, Onja H; Dunham, Amy E

    2016-08-01

    Frugivores are the main seed dispersers in many ecosystems, such that behaviorally driven, nonrandom patterns of seed dispersal are a common process; but patterns are poorly understood. Characterizing these patterns may be essential for understanding spatial organization of fruiting trees and drivers of seed-dispersal limitation in biodiverse forests. To address this, we studied resulting spatial associations between dispersed seeds and adult tree neighbors in a diverse rainforest in Madagascar, using a temporal and phylogenetic approach. Data show that by using fruiting trees as seed-dispersal foci, frugivores bias seed dispersal under conspecific adults and under heterospecific trees that share dispersers and fruiting time with the dispersed species. Frugivore-mediated seed dispersal also resulted in nonrandom phylogenetic associations of dispersed seeds with their nearest adult neighbors, in nine out of the 16 months of our study. However, these nonrandom phylogenetic associations fluctuated unpredictably over time, ranging from clustered to overdispersed. The spatial and phylogenetic template of seed dispersal did not translate to similar patterns of association in adult tree neighborhoods, suggesting the importance of post-dispersal processes in structuring plant communities. Results suggest that frugivore-mediated seed dispersal is important for structuring early stages of plant-plant associations, setting the template for post-dispersal processes that influence ultimate patterns of plant recruitment. Importantly, if biased patterns of dispersal are common in other systems, frugivores may promote tree coexistence in biodiverse forests by limiting the frequency and diversity of heterospecific interactions of seeds they disperse. © 2016 by the Ecological Society of America.

  20. Consistent individual differences in seed disperser quality in a seed-eating fish

    NARCIS (Netherlands)

    Pollux, Bart J.A.

    2017-01-01

    Animal-mediated seed dispersal (zoochory) is considered to be an important mechanism regulating biological processes at larger spatial scales. To date, intra-specific variation in seed disperser quality within seed-dispersing animals has not been studied. Here, I employed seed feeding trials to

  1. Gibbons (Nomascus gabriellae) provide key seed dispersal for the Pacific walnut (Dracontomelon dao), in Asia's lowland tropical forest

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    Hai, Bach Thanh; Chen, Jin; McConkey, Kim R.; Dayananda, Salindra K.

    2018-04-01

    Understanding the mutualisms between frugivores and plants is essential for developing successful forest management and conservation strategies, especially in tropical rainforests where the majority of plants are dispersed by animals. Gibbons are among the most effective seed dispersers in South East Asia's tropical forests, but are also one of the highly threatened arboreal mammals in the region. Here we studied the seed dispersal of the Pacific walnut (Dracontomelon dao), a canopy tree which produces fruit that are common in the diet of the endangered southern yellow-cheeked crested gibbon (Nomascus gabriellae). We found that gibbons were the most effective disperser for this species; they consumed approximately 45% of the fruit crop, which was four times more than that consumed by macaques - the only other legitimate disperser. Gibbons tracked the temporal (but not spatial) abundance of ripe fruits, indicating this fruit was a preferred species for the gibbon. Both gibbons and macaques dispersed the majority (>90%) of the seeds at least 20 m away from parent crowns, with mean dispersal distances by gibbons measuring 179.3 ± 98.0 m (range: 4-425 m). Seeds defecated by gibbons germinated quicker and at greater rates than seeds spat by macaques, or in undispersed fruits. Gibbon-dispersed seeds were also more likely to be removed by unknown seed predators or unknown secondary dispersers. Overall, gibbons play a key role in the regeneration of the Pacific walnut. Our findings have significant implications both for the management of the Pacific walnut tree dominating tropical rainforest as well as the reintroduction program of the Southern yellow-cheeked crested gibbon.

  2. Oak habitat recovery on California's largest islands: Scenarios for the role of corvid seed dispersal

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    Pesendorfer, Mario B.; Baker, Christopher M.; Stringer, Martin; McDonald-Madden, Eve; Bode, Michael; McEachern, A. Kathryn; Morrison, Scott A.; Sillett, T. Scott

    2018-01-01

    Seed dispersal by birds is central to the passive restoration of many tree communities. Reintroduction of extinct seed dispersers can therefore restore degraded forests and woodlands. To test this, we constructed a spatially explicit simulation model, parameterized with field data, to consider the effect of different seed dispersal scenarios on the extent of oak populations. We applied the model to two islands in California's Channel Islands National Park (USA), one of which has lost a key seed disperser.We used an ensemble modelling approach to simulate island scrub oak (Quercus pacifica) demography. The model was developed and trained to recreate known population changes over a 20-year period on 250-km2 Santa Cruz Island, and incorporated acorn dispersal by island scrub-jays (Aphelocoma insularis), deer mice (Peromyscus maniculatus) and gravity, as well as seed predation. We applied the trained model to 215-km2 Santa Rosa Island to examine how reintroducing island scrub-jays would affect the rate and pattern of oak population expansion. Oak habitat on Santa Rosa Island has been greatly reduced from its historical extent due to past grazing by introduced ungulates, the last of which were removed by 2011.Our simulation model predicts that a seed dispersal scenario including island scrub-jays would increase the extent of the island scrub oak population on Santa Rosa Island by 281% over 100 years, and by 544% over 200 years. Scenarios without jays would result in little expansion. Simulated long-distance seed dispersal by jays also facilitates establishment of discontinuous patches of oaks, and increases their elevational distribution.Synthesis and applications. Scenario planning provides powerful decision support for conservation managers. We used ensemble modelling of plant demographic and seed dispersal processes to investigate whether the reintroduction of seed dispersers could provide cost-effective means of achieving broader ecosystem restoration goals on

  3. Seed-dispersal distributions by trumpeter hornbills in fragmented landscapes

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    Lenz, Johanna; Fiedler, Wolfgang; Caprano, Tanja; Friedrichs, Wolfgang; Gaese, Bernhard H.; Wikelski, Martin; Böhning-Gaese, Katrin

    2011-01-01

    Frugivorous birds provide important ecosystem services by transporting seeds of fleshy fruited plants. It has been assumed that seed-dispersal kernels generated by these animals are generally leptokurtic, resulting in little dispersal among habitat fragments. However, little is known about the seed-dispersal distribution generated by large frugivorous birds in fragmented landscapes. We investigated movement and seed-dispersal patterns of trumpeter hornbills (Bycanistes bucinator) in a fragmented landscape in South Africa. Novel GPS loggers provide high-quality location data without bias against recording long-distance movements. We found a very weakly bimodal seed-dispersal distribution with potential dispersal distances up to 14.5 km. Within forest, the seed-dispersal distribution was unimodal with an expected dispersal distance of 86 m. In the fragmented agricultural landscape, the distribution was strongly bimodal with peaks at 18 and 512 m. Our results demonstrate that seed-dispersal distributions differed when birds moved in different habitat types. Seed-dispersal distances in fragmented landscapes show that transport among habitat patches is more frequent than previously assumed, allowing plants to disperse among habitat patches and to track the changing climatic conditions. PMID:21177686

  4. Modelling long-distance seed dispersal in heterogeneous landscapes.

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    Levey, Douglas, J.; Tewlsbury, Joshua, J.; Bolker, Benjamin, M.

    2008-01-01

    1. Long-distance seed dispersal is difficult to measure, yet key to understanding plant population dynamics and community composition. 2. We used a spatially explicit model to predict the distribution of seeds dispersed long distances by birds into habitat patches of different shapes. All patches were the same type of habitat and size, but varied in shape. They occurred in eight experimental landscapes, each with five patches of four different shapes, 150 m apart in a matrix of mature forest. The model was parameterized with smallscale movement data collected from field observations of birds. In a previous study we validated the model by testing its predictions against observed patterns of seed dispersal in real landscapes with the same types and spatial configuration of patches as in the model. 3. Here we apply the model more broadly, examining how patch shape influences the probability of seed deposition by birds into patches, how dispersal kernels (distributions of dispersal distances) vary with patch shape and starting location, and how movement of seeds between patches is affected by patch shape. 4. The model predicts that patches with corridors or other narrow extensions receive higher numbers of seeds than patches without corridors or extensions. This pattern is explained by edgefollowing behaviour of birds. Dispersal distances are generally shorter in heterogeneous landscapes (containing patchy habitat) than in homogeneous landscapes, suggesting that patches divert the movement of seed dispersers, ‘holding’ them long enough to increase the probability of seed defecation in the patches. Dispersal kernels for seeds in homogeneous landscapes were smooth, whereas those in heterogenous landscapes were irregular. In both cases, long-distance (> 150 m) dispersal was surprisingly common, usually comprising approximately 50% of all dispersal events. 5. Synthesis . Landscape heterogeneity has a large influence on patterns of long-distance seed dispersal. Our

  5. Seed mass and mast seeding enhance dispersal by a neotropical scatter-hoarding rodent

    NARCIS (Netherlands)

    Jansen, P.A.; Bongers, F.J.J.M.; Hemerik, L.

    2004-01-01

    Many tree species that depend on scatter-hoarding animals for seed dispersal produce massive crops of large seeds at irregular intervals. Mast seeding and large seed size in these species have been explained as adaptations to increase animal dispersal and reduce predation. We studied how seed size

  6. Seed dispersal anachronisms: rethinking the fruits extinct megafauna ate.

    Directory of Open Access Journals (Sweden)

    Paulo R Guimarães

    Full Text Available BACKGROUND: Some neotropical, fleshy-fruited plants have fruits structurally similar to paleotropical fruits dispersed by megafauna (mammals > 10(3 kg, yet these dispersers were extinct in South America 10-15 Kyr BP. Anachronic dispersal systems are best explained by interactions with extinct animals and show impaired dispersal resulting in altered seed dispersal dynamics. METHODOLOGY/PRINCIPAL FINDINGS: We introduce an operational definition of megafaunal fruits and perform a comparative analysis of 103 Neotropical fruit species fitting this dispersal mode. We define two megafaunal fruit types based on previous analyses of elephant fruits: fruits 4-10 cm in diameter with up to five large seeds, and fruits > 10 cm diameter with numerous small seeds. Megafaunal fruits are well represented in unrelated families such as Sapotaceae, Fabaceae, Solanaceae, Apocynaceae, Malvaceae, Caryocaraceae, and Arecaceae and combine an overbuilt design (large fruit mass and size with either a single or few ( 100 seeds. Within-family and within-genus contrasts between megafaunal and non-megafaunal groups of species indicate a marked difference in fruit diameter and fruit mass but less so for individual seed mass, with a significant trend for megafaunal fruits to have larger seeds and seediness. CONCLUSIONS/SIGNIFICANCE: Megafaunal fruits allow plants to circumvent the trade-off between seed size and dispersal by relying on frugivores able to disperse enormous seed loads over long-distances. Present-day seed dispersal by scatter-hoarding rodents, introduced livestock, runoff, flooding, gravity, and human-mediated dispersal allowed survival of megafauna-dependent fruit species after extinction of the major seed dispersers. Megafauna extinction had several potential consequences, such as a scale shift reducing the seed dispersal distances, increasingly clumped spatial patterns, reduced geographic ranges and limited genetic variation and increased among

  7. Invasive pathogen threatens bird-pine mutualism: Implications for sustaining a high-elevation ecosystem

    Science.gov (United States)

    Shawn T. McKinney; Carl E. Fiedler; Diana F. Tomback

    2009-01-01

    Human-caused disruptions to seed-dispersal mutualisms increase the extinction risk for both plant and animal species. Large-seeded plants can be particularly vulnerable due to highly specialized dispersal systems and no compensatory regeneration mechanisms. Whitebark pine (Pinus albicaulis), a keystone subalpine species, obligately depends upon the Clark's...

  8. Crop size influences pre-dispersal seed predation in the Brazilian Cerrado

    Directory of Open Access Journals (Sweden)

    Alexander V. Christianini

    2017-11-01

    Full Text Available ABSTRACT Many pre-dispersal seed predators are specialized insects that rely on seeds for larval development. These insects may respond to the amount of seeds produced by a plant (i.e. crop size, increasing the proportion of seeds damaged with increases in seed numbers. Large seeds have more resources and spend more time in plants to complete their development and are probably more prone to be preyed on by those insects than small seeds. Here I tested how crop size and seed mass influence pre-dispersal seed predation in plants from the Cerrado savannas of Brazil. I related plant crop size to pre-dispersal seed predation for Xylopia aromatica and Erythroxylum pelleterianum. A literature review was performed to test if seed mass may explain among-species differences in pre-dispersal seed predation. Pre-dispersal losses increased proportionally to crop size in the two species investigated, but some species show positive or no density-dependent seed predation in literature, indicating that seed losses are not a simple function of crop sizes. Seed mass did not explain pre-dispersal seed loss differences among 14 species with data available. Pre-dispersal losses are often small and probably less important than seed dispersal and establishment limitation for plant recruitment in Cerrado savannas.

  9. Seed dispersers, seed predators, and browsers act synergistically as biotic filters in a mosaic landscape.

    Directory of Open Access Journals (Sweden)

    Regino Zamora

    Full Text Available In this study, we analize the functional influence of animals on the plants they interact with in a mediterranean mountain. We hypothesise that seed dispersers, seed predators, and browsers can act as biotic filters for plant communities. We analyse the combined effects of mutualistic (seed dispersal and antagonistic (seed predation, herbivory animal interactions in a mosaic landscape of Mediterranean mountains, basing our results on observational and experimental field. Most of the dispersed seeds came from tree species, whereas the population of saplings was composed predominantly of zoochorous shrub species. Seed predators preferentially consumed seeds from tree species, whereas seeds from the dominant fleshy-fruited shrubs had a higher probability of escaping these predators. The same pattern was repeated among the different landscape units by browsers, since they browsed selectively and far more intensely on tree-species saplings than on the surrounding shrubs. In synthesis, our work identifies the major biotic processes that appear to be favoring a community dominated by shrubs versus trees because seed dispersers, predators, and herbivores together favored shrub dispersal and establishment versus trees.

  10. Seed source, seed traits, and frugivore habits: Implications for dispersal quality of two sympatric primates.

    Science.gov (United States)

    Benítez-Malvido, Julieta; González-Di Pierro, Ana Ma; Lombera, Rafael; Guillén, Susana; Estrada, Alejandro

    2014-06-01

    • Premise of the study: Frugivore selection of fruits and treatment of seeds together with seed deposition site are crucial for the population dynamics of vertebrate-dispersed plants. However, frugivore species may influence dispersal quality differently even when feeding on the same fruit species and, while animals disperse some seeds, others simply fall beneath the parent plant.• Methods: In southern Mexico, we investigated to see if within-species seed traits (i.e., length, width, weight, and volume) and germination success differed according to seed source. For five tropical tree species we obtained ingested seeds from two sources, howler monkey (Alouatta pigra) and spider monkey (Ateles geoffroyi) feces; and noningested seeds from two sources, the ground and tree crowns (with predispersed seeds used as control).• Key results: A principal components' analysis showed that traits of seeds ingested by howler monkeys differed from other sources while seeds ingested by spider monkeys were similar to noningested seeds. Howlers consumed on average the larger seeds in Ampelocera hottlei, Brosimum lactescens, and Dialium guianense. Both primate species consumed the smaller seeds in Spondias mombin, while no seed trait differences among seed sources were found in Spondias radlkoferi. For all five tree species, germination rate was greatest for seeds ingested by howler monkeys.• Conclusions: For the studied plant species, seed ingestion by howler monkeys confers higher dispersal quality than ingestion by spider monkeys or nondispersal. Dispersal services of both primate species, however, are not redundant and may contribute to germination heterogeneity within plant populations in tropical forests. © 2014 Botanical Society of America, Inc.

  11. Uncoupling the effects of seed predation and seed dispersal by granivorous ants on plant population dynamics.

    Directory of Open Access Journals (Sweden)

    Xavier Arnan

    Full Text Available Secondary seed dispersal is an important plant-animal interaction, which is central to understanding plant population and community dynamics. Very little information is still available on the effects of dispersal on plant demography and, particularly, for ant-seed dispersal interactions. As many other interactions, seed dispersal by animals involves costs (seed predation and benefits (seed dispersal, the balance of which determines the outcome of the interaction. Separate quantification of each of them is essential in order to understand the effects of this interaction. To address this issue, we have successfully separated and analyzed the costs and benefits of seed dispersal by seed-harvesting ants on the plant population dynamics of three shrub species with different traits. To that aim a stochastic, spatially-explicit individually-based simulation model has been implemented based on actual data sets. The results from our simulation model agree with theoretical models of plant response dependent on seed dispersal, for one plant species, and ant-mediated seed predation, for another one. In these cases, model predictions were close to the observed values at field. Nonetheless, these ecological processes did not affect in anyway a third species, for which the model predictions were far from the observed values. This indicates that the balance between costs and benefits associated to secondary seed dispersal is clearly related to specific traits. This study is one of the first works that analyze tradeoffs of secondary seed dispersal on plant population dynamics, by disentangling the effects of related costs and benefits. We suggest analyzing the effects of interactions on population dynamics as opposed to merely analyzing the partners and their interaction strength.

  12. Extremely long-distance seed dispersal by an overfished Amazonian frugivore.

    Science.gov (United States)

    Anderson, Jill T; Nuttle, Tim; Saldaña Rojas, Joe S; Pendergast, Thomas H; Flecker, Alexander S

    2011-11-22

    Throughout Amazonia, overfishing has decimated populations of fruit-eating fishes, especially the large-bodied characid, Colossoma macropomum. During lengthy annual floods, frugivorous fishes enter vast Amazonian floodplains, consume massive quantities of fallen fruits and egest viable seeds. Many tree and liana species are clearly specialized for icthyochory, and seed dispersal by fish may be crucial for the maintenance of Amazonian wetland forests. Unlike frugivorous mammals and birds, little is known about seed dispersal effectiveness of fishes. Extensive mobility of frugivorous fish could result in extremely effective, multi-directional, long-distance seed dispersal. Over three annual flood seasons, we tracked fine-scale movement patterns and habitat use of wild Colossoma, and seed retention in the digestive tracts of captive individuals. Our mechanistic model predicts that Colossoma disperses seeds extremely long distances to favourable habitats. Modelled mean dispersal distances of 337-552 m and maximum of 5495 m are among the longest ever reported. At least 5 per cent of seeds are predicted to disperse 1700-2110 m, farther than dispersal by almost all other frugivores reported in the literature. Additionally, seed dispersal distances increased with fish size, but overfishing has biased Colossoma populations to smaller individuals. Thus, overexploitation probably disrupts an ancient coevolutionary relationship between Colossoma and Amazonian plants.

  13. Interactions between seed traits and digestive processes determine the germinability of bird-dispersed seeds.

    Science.gov (United States)

    Kleyheeg, Erik; Claessens, Mascha; Soons, Merel B

    2018-01-01

    Waterbirds disperse a wide range of plant seeds via their guts, promoting biotic connectivity between isolated habitat patches. However, the intensity of digestive forces encountered by seeds, and therefore their potential to survive digestive tract passage, varies within and between waterbird species. Here, we investigate under controlled conditions how the interaction between seed traits and digestive strategies affect the germinability of seeds following waterbird-mediated dispersal. We exposed seeds of 30 wetland plant species to the main digestive processes in the dabbling duck digestive system: mechanical, chemical and intestinal digestion. These were simulated by 1) a pressure test and scarification treatment, 2) incubation in simulated gastric juice, and 3) incubation in intestinal contents of culled mallards (Anas platyrhynchos). We evaluated their separate and combined effects on seed germination, and identified the role of seed size and seed coat traits in resisting the digestive forces. Seeds were generally resistant to separate digestive processes, but highly sensitive to a combination. Resistance to mechanical break-down was reduced by up to 80% by chemical pre-treatment, especially for seeds with permeable coats. Scarified seeds were 12-17% more vulnerable to chemical and intestinal digestive processes than undamaged seeds. Large seeds and seeds with thin, permeable coats were particularly sensitive to chemical and intestinal digestion. These results indicate that efficient digestion of seeds requires multiple digestive processes. The gizzard, responsible for mechanical digestion, plays a key role in seed survival. Omnivorous birds, which have relatively light gizzards compared to pure herbivores or granivores, are thus most likely to disperse seeds successfully. Regardless of digestive strategy, small seeds with tough seed coats are most resistant to digestion and may be adapted to endozoochorous dispersal by waterbirds.

  14. Interactions between seed traits and digestive processes determine the germinability of bird-dispersed seeds

    Science.gov (United States)

    Soons, Merel B.

    2018-01-01

    Waterbirds disperse a wide range of plant seeds via their guts, promoting biotic connectivity between isolated habitat patches. However, the intensity of digestive forces encountered by seeds, and therefore their potential to survive digestive tract passage, varies within and between waterbird species. Here, we investigate under controlled conditions how the interaction between seed traits and digestive strategies affect the germinability of seeds following waterbird-mediated dispersal. We exposed seeds of 30 wetland plant species to the main digestive processes in the dabbling duck digestive system: mechanical, chemical and intestinal digestion. These were simulated by 1) a pressure test and scarification treatment, 2) incubation in simulated gastric juice, and 3) incubation in intestinal contents of culled mallards (Anas platyrhynchos). We evaluated their separate and combined effects on seed germination, and identified the role of seed size and seed coat traits in resisting the digestive forces. Seeds were generally resistant to separate digestive processes, but highly sensitive to a combination. Resistance to mechanical break-down was reduced by up to 80% by chemical pre-treatment, especially for seeds with permeable coats. Scarified seeds were 12–17% more vulnerable to chemical and intestinal digestive processes than undamaged seeds. Large seeds and seeds with thin, permeable coats were particularly sensitive to chemical and intestinal digestion. These results indicate that efficient digestion of seeds requires multiple digestive processes. The gizzard, responsible for mechanical digestion, plays a key role in seed survival. Omnivorous birds, which have relatively light gizzards compared to pure herbivores or granivores, are thus most likely to disperse seeds successfully. Regardless of digestive strategy, small seeds with tough seed coats are most resistant to digestion and may be adapted to endozoochorous dispersal by waterbirds. PMID:29614085

  15. Forest rodents provide directed dispersal of Jeffrey pine seeds

    Science.gov (United States)

    Briggs, J.S.; Wall, S.B.V.; Jenkins, S.H.

    2009-01-01

    Some species of animals provide directed dispersal of plant seeds by transporting them nonrandomly to microsites where their chances of producing healthy seedlings are enhanced. We investigated whether this mutualistic interaction occurs between granivorous rodents and Jeffrey pine (Pinus jeffreyi) in the eastern Sierra Nevada by comparing the effectiveness of random abiotic seed dispersal with the dispersal performed by four species of rodents: deer mice (Peromyscus maniculatus), yellow-pine and long-eared chipmunks (Tamias amoenus and T. quadrimaculatus), and golden-mantled ground squirrels (Spermophilus lateralis). We conducted two caching studies using radio-labeled seeds, the first with individual animals in field enclosures and the second with a community of rodents in open forest. We used artificial caches to compare the fates of seeds placed at the range of microsites and depths used by animals with the fates of seeds dispersed abiotically. Finally, we examined the distribution and survival of naturally establishing seedlings over an eight-year period.Several lines of evidence suggested that this community of rodents provided directed dispersal. Animals preferred to cache seeds in microsites that were favorable for emergence or survival of seedlings and avoided caching in microsites in which seedlings fared worst. Seeds buried at depths typical of animal caches (5–25 mm) produced at least five times more seedlings than did seeds on the forest floor. The four species of rodents differed in the quality of dispersal they provided. Small, shallow caches made by deer mice most resembled seeds dispersed by abiotic processes, whereas many of the large caches made by ground squirrels were buried too deeply for successful emergence of seedlings. Chipmunks made the greatest number of caches within the range of depths and microsites favorable for establishment of pine seedlings. Directed dispersal is an important element of the population dynamics of Jeffrey pine, a

  16. Global patterns in post-dispersal seed removal by invertebrates and vertebrates.

    Science.gov (United States)

    Peco, Begoña; Laffan, Shawn W; Moles, Angela T

    2014-01-01

    It is commonly accepted that species interactions such as granivory are more intense in the tropics. However, this has rarely been tested. A global dataset of post-dispersal seed removal by invertebrates and vertebrates for 79 native plant species from semi-natural and natural terrestrial habitats ranging from 55° N to 45° S, was compiled from the global literature to test the hypothesis that post-dispersal seed removal by invertebrates and vertebrates is more intense at lower latitudes. We also quantified the relationship between post-dispersal seed removal by vertebrates and by invertebrates to global climatic features including temperature, actual evapotranspiration (AET) and rainfall seasonality. Linear mixed effect models were applied to describe the relationships between seed removal and latitude, hemisphere and climatic variables controlling for the effect of seed mass. Post-dispersal seed removal by invertebrates was negatively related to latitude. In contrast, post-dispersal seed removal by vertebrates was positively but weakly related to latitude. Mean annual temperature and actual evapotranspiration were positively related to post-dispersal seed removal by invertebrates, but not to post-dispersal seed removal by vertebrates, which was only marginally negatively related to rainfall seasonality. The inclusion of seed mass improved the fit of all models, but the term for seed mass was not significant in any model. Although a good climatic model for predicting post-dispersal seed predation by vertebrates at the global level was not found, our results suggest different and opposite latitudinal patterns of post-dispersal seed removal by invertebrates vs vertebrates. This is the first time that a negative relationship between post-dispersal seed removal by invertebrates and latitude, and a positive relationship with temperature and AET have been documented at a global-scale. These results have important implications for understanding global patterns in plant

  17. Does an ant-dispersed plant, Viola reichenbachiana, suffer from reduced seed dispersal under inundation disturbances?

    NARCIS (Netherlands)

    Prinzing, A.; Dauber, J.; Hammer, E.; Hammouti, N.; Bohning-Gaese, K.

    2008-01-01

    Many plant species use ants as seed dispersers. This dispersal mode is considered to be susceptible to disturbances, but the effect of natural, small-scale disturbances is still unknown. We investigated how small-scale disturbances due to inundation affect seed dispersal in Viola reichenbachiana, a

  18. Seed Dispersal Potential of Asian Elephants

    DEFF Research Database (Denmark)

    Harich, Franziska K.; Treydte, Anna Christina; Ogutu, Joseph Ochieng

    2016-01-01

    Elephants, the largest terrestrial mega-herbivores, play an important ecological role in maintaining forest ecosystem diversity. While several plant species strongly rely on African elephants (Loxodonta africana; L. cyclotis) as seed dispersers, little is known about the dispersal potential of As...

  19. Functional redundancy and complementarities of seed dispersal by the last neotropical megafrugivores.

    Science.gov (United States)

    Bueno, Rafael S; Guevara, Roger; Ribeiro, Milton C; Culot, Laurence; Bufalo, Felipe S; Galetti, Mauro

    2013-01-01

    Functional redundancy has been debated largely in ecology and conservation, yet we lack detailed empirical studies on the roles of functionally similar species in ecosystem function. Large bodied frugivores may disperse similar plant species and have strong impact on plant recruitment in tropical forests. The two largest frugivores in the neotropics, tapirs (Tapirus terrestris) and muriquis (Brachyteles arachnoides) are potential candidates for functional redundancy on seed dispersal effectiveness. Here we provide a comparison of the quantitative, qualitative and spatial effects on seed dispersal by these megafrugivores in a continuous Brazilian Atlantic forest. We found a low overlap of plant species dispersed by both muriquis and tapirs. A group of 35 muriquis occupied an area of 850 ha and dispersed 5 times more plant species, and 13 times more seeds than 22 tapirs living in the same area. Muriquis dispersed 2.4 times more seeds in any random position than tapirs. This can be explained mainly because seed deposition by muriquis leaves less empty space than tapirs. However, tapirs are able to disperse larger seeds than muriquis and move them into sites not reached by primates, such as large forest gaps, open areas and fragments nearby. Based on published information we found 302 plant species that are dispersed by at least one of these megafrugivores in the Brazilian Atlantic forest. Our study showed that both megafrugivores play complementary rather than redundant roles as seed dispersers. Although tapirs disperse fewer seeds and species than muriquis, they disperse larger-seeded species and in places not used by primates. The selective extinction of these megafrugivores will change the spatial seed rain they generate and may have negative effects on the recruitment of several plant species, particularly those with large seeds that have muriquis and tapirs as the last living seed dispersers.

  20. Functional Redundancy and Complementarities of Seed Dispersal by the Last Neotropical Megafrugivores

    Science.gov (United States)

    Bueno, Rafael S.; Guevara, Roger; Ribeiro, Milton C.; Culot, Laurence; Bufalo, Felipe S.; Galetti, Mauro

    2013-01-01

    Background Functional redundancy has been debated largely in ecology and conservation, yet we lack detailed empirical studies on the roles of functionally similar species in ecosystem function. Large bodied frugivores may disperse similar plant species and have strong impact on plant recruitment in tropical forests. The two largest frugivores in the neotropics, tapirs (Tapirus terrestris) and muriquis (Brachyteles arachnoides) are potential candidates for functional redundancy on seed dispersal effectiveness. Here we provide a comparison of the quantitative, qualitative and spatial effects on seed dispersal by these megafrugivores in a continuous Brazilian Atlantic forest. Methodology/Principal Findings We found a low overlap of plant species dispersed by both muriquis and tapirs. A group of 35 muriquis occupied an area of 850 ha and dispersed 5 times more plant species, and 13 times more seeds than 22 tapirs living in the same area. Muriquis dispersed 2.4 times more seeds in any random position than tapirs. This can be explained mainly because seed deposition by muriquis leaves less empty space than tapirs. However, tapirs are able to disperse larger seeds than muriquis and move them into sites not reached by primates, such as large forest gaps, open areas and fragments nearby. Based on published information we found 302 plant species that are dispersed by at least one of these megafrugivores in the Brazilian Atlantic forest. Conclusions/Significance Our study showed that both megafrugivores play complementary rather than redundant roles as seed dispersers. Although tapirs disperse fewer seeds and species than muriquis, they disperse larger-seeded species and in places not used by primates. The selective extinction of these megafrugivores will change the spatial seed rain they generate and may have negative effects on the recruitment of several plant species, particularly those with large seeds that have muriquis and tapirs as the last living seed dispersers. PMID

  1. Functional redundancy and complementarities of seed dispersal by the last neotropical megafrugivores.

    Directory of Open Access Journals (Sweden)

    Rafael S Bueno

    Full Text Available Functional redundancy has been debated largely in ecology and conservation, yet we lack detailed empirical studies on the roles of functionally similar species in ecosystem function. Large bodied frugivores may disperse similar plant species and have strong impact on plant recruitment in tropical forests. The two largest frugivores in the neotropics, tapirs (Tapirus terrestris and muriquis (Brachyteles arachnoides are potential candidates for functional redundancy on seed dispersal effectiveness. Here we provide a comparison of the quantitative, qualitative and spatial effects on seed dispersal by these megafrugivores in a continuous Brazilian Atlantic forest.We found a low overlap of plant species dispersed by both muriquis and tapirs. A group of 35 muriquis occupied an area of 850 ha and dispersed 5 times more plant species, and 13 times more seeds than 22 tapirs living in the same area. Muriquis dispersed 2.4 times more seeds in any random position than tapirs. This can be explained mainly because seed deposition by muriquis leaves less empty space than tapirs. However, tapirs are able to disperse larger seeds than muriquis and move them into sites not reached by primates, such as large forest gaps, open areas and fragments nearby. Based on published information we found 302 plant species that are dispersed by at least one of these megafrugivores in the Brazilian Atlantic forest.Our study showed that both megafrugivores play complementary rather than redundant roles as seed dispersers. Although tapirs disperse fewer seeds and species than muriquis, they disperse larger-seeded species and in places not used by primates. The selective extinction of these megafrugivores will change the spatial seed rain they generate and may have negative effects on the recruitment of several plant species, particularly those with large seeds that have muriquis and tapirs as the last living seed dispersers.

  2. Competition as a mechanism structuring mutualisms

    Science.gov (United States)

    Robert J. Warren; Itamar Giladi; Mark A. Bradford

    2014-01-01

    Summary 1. Hutchinsonian niche theory posits that organisms have fundamental abiotic resource requirements from which they are limited by competition. Organisms also have fundamental biotic requirements, such as mutualists, for which they also might compete. 2. We test this idea with a widespread ant–plant mutualism. Ant-mediated seed dispersal (myrmecochory) in...

  3. One-dimensional Analytical Modelling of Floating Seed Dispersal in Tidal Channels

    Science.gov (United States)

    Shi, W.; Purnama, A.; Shao, D.; Cui, B.; Gao, W.

    2017-12-01

    Seed dispersal is a primary factor influencing plant community development, and thus plays a critical role in maintaining wetland ecosystem functioning. However, compared with fluvial seed dispersal of riparian plants, dispersal of saltmarsh plant seeds in tidal channels is much less studied due to its complex behavior, and relevant mathematical modelling is particularly lacking. In this study, we developed a one-dimensional advection-dispersion model to explore the patterns of tidal seed dispersal. Oscillatory tidal current and water depth were assumed to represent the tidal effects. An exponential decay coefficient λ was introduced to account for seed deposition and retention. Analytical solution in integral form was derived using Green's function and further evaluated using numerical integration. The developed model was applied to simulate Spartina densiflora seed dispersal in a tidal channel located at the Mad River Slough in North Humboldt Bay, California, USA, to demonstrate its practical applicability. Model predictions agree satisfactorily with field observation and simulation results from Delft3D numerical model. Sensitivity analyses were also conducted to evaluate the effects of varying calibrated parameters on model predictions. The range of the seed dispersion as well as the distribution of the seed concentration were further analyzed through statistical parameters such as centroid displacement and variance of the seed cloud together with seed concentration contours. Implications of the modelling results on tidal marsh restoration and protection, e.g., revegetation through seed addition, were also discussed through scenario analysis. The developed analytical model provides a useful tool for ecological management of tidal marshes.

  4. Distribution of western juniper seeds across an ecotone and implications for seed dispersal processes

    Science.gov (United States)

    Western juniper forests have been the focus of extensive research and management due to range expansion and infilling that began over a century ago. Understanding juniper seed dispersal is vital to identifying processes behind increases in density and range. Dispersal of Juniperus seeds has generall...

  5. Mountain bikes as seed dispersers and their potential socio-ecological consequences.

    Science.gov (United States)

    Weiss, Fabio; Brummer, Tyler J; Pufal, Gesine

    2016-10-01

    Seed dispersal critically influences plant community composition and species distributions. Increasingly, human mediated dispersal is acknowledged as important dispersal mechanism, but we are just beginning to understand the different vectors that might play a role. We assessed the role of mountain bikes as potential dispersal vectors and associated social-ecological consequences in areas of conservation concern near Freiburg, Germany. Seed attachment and detachment on a mountain bike were measured experimentally at distances from 0 to 500 m. We assessed effects of seed traits, weather conditions, riding distance and tire combinations using generalized linear mixed effect models. Most seeds detached from the mountain bike within the first 5-20 m. However, a small proportion of seeds remained on tires after 200-500 m. Attachment was higher, and the rate of detachment slower, in semi-wet conditions and lighter seeds travelled farther. Seed dispersal by mountain bikes was moderate compared to other forms of human mediated dispersal. However, we found that lighter seeds could attach to other bike parts and remain there until cleaning which, depending on riders' preferences, might only be after 70 km and in different habitats. Ecological impacts of mountain biking are growing with the popularity of the activity. We demonstrate that mountain bikes are effective seeds dispersers at landscape scales. Thus, management to mitigate their potential to spread non-native species is warranted. We suggest bike cleaning between rides, control of non-native species at trailheads and increased awareness for recreationalists in areas of conservation concern to mitigate the potential negative consequences of seed dispersal. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Milkweed Seed Dispersal: A Means for Integrating Biology and Physics.

    Science.gov (United States)

    Bisbee, Gregory D.; Kaiser, Cheryl A.

    1997-01-01

    Describes an activity that integrates biology and physics concepts by experimenting with the seed dispersal of common milkweed or similar wind-dispersed seeds. Student teams collect seeds and measure several parameters, review principles of trajectory motion, perform experiments, and graph data. Students examine the ideas of…

  7. Internal dispersal of seeds by waterfowl: effect of seed size on gut passage time and germination patterns

    NARCIS (Netherlands)

    Figuerola, J.; Charalambidou, I.; Santamaria, L.; Green, A.J.

    2010-01-01

    Long distance dispersal may have important consequences for gene flow and community structure. The dispersal of many plants depends on transport by vertebrate seed dispersers. The shapes of seed shadows produced by vertebrates depend both on movement patterns of the dispersers and on the dynamics

  8. Frugivory and seed dispersal by tapirs: an insight on their ecological role.

    Science.gov (United States)

    O'Farrill, Georgina; Galetti, Mauro; Campos-Arceiz, Ahimsa

    2013-03-01

    Tapirs are one of the last extant megafauna species that survived the Pleistocene extinctions. Given their size and digestive system characteristics, tapirs might be the last potential seed disperser of plant species that were previously dispersed by other large mammal species that are now extinct. We compiled evidence from 39 published scientific studies showing that tapirs have a key role as seed dispersers and seed predators. Tapirs play an important role either through seed predation or by facilitating the recruitment of seeds over long distances, therefore influencing the diversity of plant species in the ecosystem. Neotropical tapirs might have a unique role as long-distance seed dispersers of large seeds (tapir diet, more information is needed on the identification of seed traits that allow the survival of seeds in the tapir's gut. Moreover, further studies are necessary on the role of tapirs as seed dispersers and predators; in particular considering spatial patterns of dispersed seeds, seed viability, effect of dung, and seed density in tapir latrines, and the effect of deposition sites on germination and seedling survival. Because all tapir species are highly threatened, it is paramount to identify gaps in our knowledge on the ecological role of tapirs and, in particular, on critical and endangered plant-tapir interactions to avoid possible trophic cascading effects on ecosystem function. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

  9. Seed dispersal by vertebrates in Madagascar's forests: review and ...

    African Journals Online (AJOL)

    seeds. Thus, understanding plant - frugivore interactions is of critical importance for the conservation and ... ance of many plant species on frugivores for their dispersal. Understanding this ecosystem service can provide us ... edge of this ecosystem service in Madagascar. Understanding seed dispersal is important because ...

  10. Myrmecochory and short-term seed fate in Rhamnus alaternus: Ant species and seed characteristics

    Science.gov (United States)

    Bas, J. M.; Oliveras, J.; Gómez, C.

    2009-05-01

    Benefits conferred on plants in ant-mediated seed dispersal mutualisms (myrmecochory) depend on the fate of transported seeds. We studied the effects of elaiosome presence, seed size and seed treatment (with and without passage through a bird's digestive tract) on short-term seed fate in Rhamnus alaternus. In our study, we define short-term seed, or initial, seed fate, as the location where ants release the seeds after ant contact with it. The elaiosomes had the most influence on short-term fate, i.e. whether or not seeds were transported to the nest. The workers usually transported big seeds more often than small ones, but small ants did not transport large seeds. Effect of seed size on transport depended on the ant species and on the treatment of the seed (manual extraction simulating a direct fall from the parent plant vs. bird deposition corresponding to preliminary primary dispersal). Probability of removal of elaiosome-bearing seeds to the nest by Aphaenogaster senilis increased with increasing seed weight.

  11. Defaunation leads to interaction deficits, not interaction compensation, in an island seed dispersal network.

    Science.gov (United States)

    Fricke, Evan C; Tewksbury, Joshua J; Rogers, Haldre S

    2018-01-01

    Following defaunation, the loss of interactions with mutualists such as pollinators or seed dispersers may be compensated through increased interactions with remaining mutualists, ameliorating the negative cascading impacts on biodiversity. Alternatively, remaining mutualists may respond to altered competition by reducing the breadth or intensity of their interactions, exacerbating negative impacts on biodiversity. Despite the importance of these responses for our understanding of the dynamics of mutualistic networks and their response to global change, the mechanism and magnitude of interaction compensation within real mutualistic networks remains largely unknown. We examined differences in mutualistic interactions between frugivores and fruiting plants in two island ecosystems possessing an intact or disrupted seed dispersal network. We determined how changes in the abundance and behavior of remaining seed dispersers either increased mutualistic interactions (contributing to "interaction compensation") or decreased interactions (causing an "interaction deficit") in the disrupted network. We found a "rich-get-richer" response in the disrupted network, where remaining frugivores favored the plant species with highest interaction frequency, a dynamic that worsened the interaction deficit among plant species with low interaction frequency. Only one of five plant species experienced compensation and the other four had significant interaction deficits, with interaction frequencies 56-95% lower in the disrupted network. These results do not provide support for the strong compensating mechanisms assumed in theoretical network models, suggesting that existing network models underestimate the prevalence of cascading mutualism disruption after defaunation. This work supports a mutualist biodiversity-ecosystem functioning relationship, highlighting the importance of mutualist diversity for sustaining diverse and resilient ecosystems. © 2017 John Wiley & Sons Ltd.

  12. The mechanics of explosive seed dispersal in orange jewelweed (Impatiens capensis).

    Science.gov (United States)

    Hayashi, Marika; Feilich, Kara L; Ellerby, David J

    2009-01-01

    Explosive dehiscence ballistically disperses seeds in a number of plant species. During dehiscence, mechanical energy stored in specialized tissues is transferred to the seeds to increase their kinetic and potential energies. The resulting seed dispersal patterns have been investigated in some ballistic dispersers, but the mechanical performance of a launch mechanism of this type has not been measured. The properties of the energy storage tissue and the energy transfer efficiency of the launch mechanism were quantified in Impatiens capensis. In this species the valves forming the seed pod wall store mechanical energy. Their mass specific energy storage capacity (124 J kg(-1)) was comparable with that of elastin and spring steel. The energy storage capacity of the pod tissues was determined by their level of hydration, suggesting a role for turgor pressure in the energy storage mechanism. During dehiscence the valves coiled inwards, collapsing the pod and ejecting the seeds. Dehiscence took 4.2+/-0.4 ms (mean +/-SEM, n=13). The estimated efficiency with which energy was transferred to the seeds was low (0.51+/-0.26%, mean +/-SEM, n=13). The mean seed launch angle (17.4+/-5.2, mean +/-SEM, n=45) fell within the range predicted by a ballistic model to maximize dispersal distance. Low ballistic dispersal efficiency or effectiveness may be characteristic of species that also utilize secondary seed dispersal mechanisms.

  13. Primary dispersal of Cytisus multiflorus seeds

    Directory of Open Access Journals (Sweden)

    Moreno Marcos, G.

    1992-12-01

    Full Text Available Current work relates to the primary dispersal of Cytisus multiflorus seeds: seed production, dispersal mechanisms, distribution of seed after dissemination and dormancy were investigated. The distribution of seed was recorded before collection; seed viabilaty and dormancy were assessed. The results indicate that the dispersion is assisted by an explosive dehiscence of the seed pod in that only 35% of the seed drop directly beneath the plant, the remainder falling further away, some reaching distances greater than 3 m. Dormancy index was found to be 98.9%.

    [es] En el presente trabajo se estudia la dispersión primaria de las semillas de Cytisus multiflorus: cuantificación de la producción, mecanismos de dispersión, distribución de las semillas tras la diseminación, y su estado de latencia. Para ello se colocaron dispositivos de recogida de las semillas debajo y alrededor de las plantas, anotando la cantidad y distancia de la calda; posteriormente eran sembradas para comprobarla viabilidad y dormición de las semillas. Los resultados indican la existencia de una dispersión por dehiscencia explosiva; solamente el 35% de las semillas caen bajo la planta, haciéndolo el resto en sus alrededores; algunas alcanzaron distancias superiores a los 3 m. El índice de dormición es de 98.9%.
    [fr] Dans le présent travail on étudie la dispersion primaire des graines de Cytisus multiflorus: quantification de la production, mécanismes de dispersion, distribution des graines après la dissémination et leur état de latence. Pour ce faire on a placé des dispositifs de récolte des graines au dessous et autour des plantes, enregistrant la quantité et la distance de la chute; après elles étaient semées pour tester la viabilité et dormance des graines. Les résultats indiquent l'existence d'une dispersion par déhiscence explosive; seulement 35% des graines tombent au-dessous de la plante, et le reste dans les

  14. Seed dispersal as an ecosystem service: frugivore loss leads to decline of a socially valued plant, Capsicum frutescens.

    Science.gov (United States)

    Egerer, Monika H; Fricke, Evan C; Rogers, Haldre S

    2018-04-01

    Species interactions, both mutualistic and antagonistic, are widely recognized as providing important ecosystem services. Fruit-eating animals influence plant recruitment by increasing germination during gut passage and moving seeds away from conspecifics. However, relative to studies focused on the importance of frugivores for plant population maintenance, few studies target frugivores as ecosystem service providers, and frugivores are underappreciated as ecosystem service providers relative to other mutualists such as pollinators. Here, we use an accidental experiment to elucidate the role of seed dispersal by frugivores for maintaining a culturally and economically important plant, the donne' sali chili (Capsicum frutescens) in the Mariana Islands. One of the islands (Guam) has lost nearly all of its native forest birds due to an invasive snake (Boiga irregularis), whereas nearby islands have relatively intact bird populations. We hypothesized that frugivore loss would influence chili recruitment and abundance, which could have economic and cultural impacts. By using video cameras, we confirmed that birds were the primary seed dispersers. We used captive bird feeding trials to obtain gut-passed seeds to use in a seedling emergence experiment. The experiment showed that gut-passed seeds emerged sooner and at a higher proportion than seeds from whole fruits. Consistent with our findings that birds benefit chilies, we observed lower chili abundance on Guam than on islands with birds. In a survey questionnaire of island residents, the majority of residents reported an association between the wild chili and local cultural values and traditions. In addition, we identified a thriving market for chili products, suggesting benefits of wild chilies to people in the Marianas both as consumers and producers. Our study therefore documents seed dispersal as both a cultural and a supporting ecosystem service. We provide a comprehensive case study on how seed-dispersed plants

  15. Epizoochory in dry forest iguanas: an overlooked seed dispersal mechanism?

    Directory of Open Access Journals (Sweden)

    Eloisa Lasso

    2015-01-01

    Full Text Available The role of animals as seed dispersal vectors is widely acknowledged, including dispersal by reptiles (saurochory. Most reports of saurochory have been via endozoochory, through feces deposition. We present the first evidence of epizoochory in Iguanas from a dry forest in Colombia via seeds attached to the snout. Our results show that seeds of a cactus Melocactus curvispinus ingested by iguana suffers from their passage through the digestive tract while seeds transported while attached to the snout germinate faster and in higher numbers. Our data suggest that we may have overlooked an alternative means of seed dispersal by lizards that does not comprise a passage through their digestive tract, and that deserves further attention for the understanding of dry forest ecology.

  16. Invasive pathogen threatens bird-pine mutualism: implications for sustaining a high-elevation ecosystem.

    Science.gov (United States)

    McKinney, Shawn T; Fiedler, Carl E; Tomback, Diana F

    2009-04-01

    Human-caused disruptions to seed-dispersal mutualisms increase the extinction risk for both plant and animal species. Large-seeded plants can be particularly vulnerable due to highly specialized dispersal systems and no compensatory regeneration mechanisms. Whitebark pine (Pinus albicaulis), a keystone subalpine species, obligately depends upon the Clark's Nutcracker (Nucifraga columbiana) for dispersal of its large, wingless seeds. Clark's Nutcracker, a facultative mutualist with whitebark pine, is sensitive to rates of energy gain, and emigrates from subalpine forests during periods of cone shortages. The invasive fungal pathogen Cronartium ribicola, which causes white pine blister rust, reduces whitebark pine cone production by killing cone-bearing branches and trees. Mortality from blister rust reaches 90% or higher in some whitebark pine forests in the Northern Rocky Mountains, USA, and the rust now occurs nearly rangewide in whitebark pine. Our objectives were to identify the minimum level of cone production necessary to elicit seed dispersal by nutcrackers and to determine how cone production is influenced by forest structure and health. We quantified forest conditions and ecological interactions between nutcrackers and whitebark pine in three Rocky Mountain ecosystems that differ in levels of rust infection and mortality. Both the frequency of nutcracker occurrence and probability of seed dispersal were strongly related to annual whitebark pine cone production, which had a positive linear association with live whitebark pine basal area, and negative linear association with whitebark pine tree mortality and rust infection. From our data, we estimated that a threshold level of approximately 1000 cones/ha is needed for a high likelihood of seed dispersal by nutcrackers (probability > or = 0.7), and that this level of cone production can be met by forests with live whitebark pine basal area > 5.0 m2/ha. The risk of mutualism disruption is greatest in northern

  17. DNA fingerprinting validates seed dispersal curves from observational studies in the neotropical legume parkia.

    Science.gov (United States)

    Heymann, Eckhard W; Lüttmann, Kathrin; Michalczyk, Inga M; Saboya, Pedro Pablo Pinedo; Ziegenhagen, Birgit; Bialozyt, Ronald

    2012-01-01

    Determining the distances over which seeds are dispersed is a crucial component for examining spatial patterns of seed dispersal and their consequences for plant reproductive success and population structure. However, following the fate of individual seeds after removal from the source tree till deposition at a distant place is generally extremely difficult. Here we provide a comparison of observationally and genetically determined seed dispersal distances and dispersal curves in a Neotropical animal-plant system. In a field study on the dispersal of seeds of three Parkia (Fabaceae) species by two Neotropical primate species, Saguinus fuscicollis and Saguinus mystax, in Peruvian Amazonia, we observationally determined dispersal distances. These dispersal distances were then validated through DNA fingerprinting, by matching DNA from the maternally derived seed coat to DNA from potential source trees. We found that dispersal distances are strongly right-skewed, and that distributions obtained through observational and genetic methods and fitted distributions do not differ significantly from each other. Our study showed that seed dispersal distances can be reliably estimated through observational methods when a strict criterion for inclusion of seeds is observed. Furthermore, dispersal distances produced by the two primate species indicated that these primates fulfil one of the criteria for efficient seed dispersers. Finally, our study demonstrated that DNA extraction methods so far employed for temperate plant species can be successfully used for hard-seeded tropical plants.

  18. Seed dispersal in six species of terrestrial orchids in Biebrza National Park (NE Poland

    Directory of Open Access Journals (Sweden)

    Emilia Brzosko

    2017-09-01

    Full Text Available Knowledge about seed dispersal is required to explain problems in ecology, phylogeography, and conservation biology. Even though seed dispersal is a fundamental mechanism to understand problems at different levels of biological organization (individual, population, species, landscape, it remains one of the least recognized processes. Similar to other groups of plants, very little is known regarding patterns and distances of seed dispersal in orchids. Orchid seeds are generally assumed to be widely dispersed by wind because of their small size and low weight. Between 2006 and 2008, we conducted a field study of the distances at which orchid seeds are dispersed, and determined factors affecting dispersal. Investigations included 13 populations of six terrestrial orchid species – Cypripedium calceolus, Cephalanthera rubra, Epipactis helleborine, Goodyera repens, Neottia ovata, and Platanthera bifolia. To evaluate seed dispersal in orchid populations, 8.5-cm Petri dishes (traps with self-adhesive paper were placed along transects, starting from a group of fruiting plants, which were considered to be the dispersal source. Seeds of the investigated orchid species were dispersed over relatively short distances. There were statistically significant negative correlations between seed density and distance from the fruiting plants. Seeds of species with taller fruiting shoots were dispersed farther than those with shorter ones (R = 0.68, p < 0.05. We discuss the causes and consequences of the dispersal patterns of orchid seeds.

  19. Biomimetics on seed dispersal: survey and insights for space exploration

    International Nuclear Information System (INIS)

    Pandolfi, Camilla; Izzo, Dario

    2013-01-01

    Seeds provide the vital genetic link and dispersal agent between successive generations of plants. Without seed dispersal as a means of reproduction, many plants would quickly die out. Because plants lack any sort of mobility and remain in the same spot for their entire lives, they rely on seed dispersal to transport their offspring throughout the environment. This can be accomplished either collectively or individually; in any case as seeds ultimately abdicate their movement, they are at the mercy of environmental factors. Thus, seed dispersal strategies are characterized by robustness, adaptability, intelligence (both behavioral and morphological), and mass and energy efficiency (including the ability to utilize environmental sources of energy available): all qualities that advanced engineering systems aim at in general, and in particular those that need to enable complex endeavors such as space exploration. Plants evolved and adapted their strategy according to their environment, and taken together, they enclose many desirable characteristics that a space mission needs to have. Understanding in detail how plants control the development of seeds, fabricate structural components for their dispersal, build molecular machineries to keep seeds dormant up to the right moment and monitor the environment to release them at the right time could provide several solutions impacting current space mission design practices. It can lead to miniaturization, higher integration and packing efficiency, energy efficiency and higher autonomy and robustness. Consequently, there would appear to be good reasons for considering biomimetic solutions from plant kingdom when designing space missions, especially to other celestial bodies, where solid and liquid surfaces, atmosphere, etc constitute and are obviously parallel with the terrestrial environment where plants evolved. In this paper, we review the current state of biomimetics on seed dispersal to improve space mission design

  20. Mountain-climbing bears protect cherry species from global warming through vertical seed dispersal.

    Science.gov (United States)

    Naoe, Shoji; Tayasu, Ichiro; Sakai, Yoichiro; Masaki, Takashi; Kobayashi, Kazuki; Nakajima, Akiko; Sato, Yoshikazu; Yamazaki, Koji; Kiyokawa, Hiroki; Koike, Shinsuke

    2016-04-25

    In a warming climate, temperature-sensitive plants must move toward colder areas, that is, higher latitude or altitude, by seed dispersal [1]. Considering that the temperature drop with increasing altitude (-0.65°C per 100 m altitude) is one hundred to a thousand times larger than that of the equivalent latitudinal distance [2], vertical seed dispersal is probably a key process for plant escape from warming temperatures. In fact, plant geographical distributions are tracking global warming altitudinally rather than latitudinally, and the extent of tracking is considered to be large in plants with better-dispersed traits (e.g., lighter seeds in wind-dispersed plants) [1]. However, no study has evaluated vertical seed dispersal itself due to technical difficulty or high cost. Here, we show using a stable oxygen isotope that black bears disperse seeds of wild cherry over several hundred meters vertically, and that the dispersal direction is heavily biased towards the mountain tops. Mountain climbing by bears following spring-to-summer plant phenology is likely the cause of this biased seed dispersal. These results suggest that spring- and summer-fruiting plants dispersed by animals may have high potential to escape global warming. Our results also indicate that the direction of vertical seed dispersal can be unexpectedly biased, and highlight the importance of considering seed dispersal direction to understand plant responses to past and future climate change. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Potential of endozoochorous seed dispersal by sheep in calcareous grasslands: correlations with seed traits.

    NARCIS (Netherlands)

    Kuiters, A.T.; Huiskes, H.P.J.

    2010-01-01

    Questions: What is the potential of sheep to serve as seed dispersers via ingestion and defecation in calcareous grasslands? Is the presence of viable seeds from dung correlated with specific seed traits? Location: Calcareous grasslands, South Limburg, the Netherlands/Belgium. Methods: Dung samples

  2. DNA Fingerprinting Validates Seed Dispersal Curves from Observational Studies in the Neotropical Legume Parkia

    Science.gov (United States)

    Heymann, Eckhard W.; Lüttmann, Kathrin; Michalczyk, Inga M.; Saboya, Pedro Pablo Pinedo; Ziegenhagen, Birgit; Bialozyt, Ronald

    2012-01-01

    Background Determining the distances over which seeds are dispersed is a crucial component for examining spatial patterns of seed dispersal and their consequences for plant reproductive success and population structure. However, following the fate of individual seeds after removal from the source tree till deposition at a distant place is generally extremely difficult. Here we provide a comparison of observationally and genetically determined seed dispersal distances and dispersal curves in a Neotropical animal-plant system. Methodology/Principal Findings In a field study on the dispersal of seeds of three Parkia (Fabaceae) species by two Neotropical primate species, Saguinus fuscicollis and Saguinus mystax, in Peruvian Amazonia, we observationally determined dispersal distances. These dispersal distances were then validated through DNA fingerprinting, by matching DNA from the maternally derived seed coat to DNA from potential source trees. We found that dispersal distances are strongly right-skewed, and that distributions obtained through observational and genetic methods and fitted distributions do not differ significantly from each other. Conclusions/Significance Our study showed that seed dispersal distances can be reliably estimated through observational methods when a strict criterion for inclusion of seeds is observed. Furthermore, dispersal distances produced by the two primate species indicated that these primates fulfil one of the criteria for efficient seed dispersers. Finally, our study demonstrated that DNA extraction methods so far employed for temperate plant species can be successfully used for hard-seeded tropical plants. PMID:22514748

  3. Cone and seed traits of two Juniperus species influence roles of frugivores and scatter-hoarding rodents as seed dispersal agents

    Science.gov (United States)

    Dimitri, Lindsay A.; Longland, William S.; Vander Wall, Stephen B.

    2017-11-01

    Seed dispersal in Juniperus is generally attributed to frugivores that consume the berry-like female cones. Some juniper cones are fleshy and resinous such as those of western juniper (Juniperus occidentalis), while others are dry and leathery such as those of Utah juniper (J. osteosperma). Rodents have been recorded harvesting Juniperus seeds and cones but are mostly considered seed predators. Our study sought to determine if rodents play a role in dispersal of western and Utah juniper seeds. We documented rodent harvest of cones and seeds of the locally-occurring juniper species and the alternate (non-local) juniper species in removal experiments at a western juniper site in northeastern California and a Utah juniper site in western Nevada. Characteristics of western and Utah juniper cones appeared to influence removal, as cones from the local juniper species were preferred at both sites. Conversely, removal of local and non-local seeds was similar. Piñon mice (Peromyscus truei) were responsible for most removal of cones and seeds at both sites. We used radioactively labeled seeds to follow seed fate and found many of these seeds in scattered caches (western juniper: 415 seeds in 82 caches, 63.0% of seeds found; Utah juniper: 458 seeds in 127 caches, 39.5% of seeds found) most of which were attributed to piñon mice. We found little evidence of frugivores dispersing Utah juniper seeds, thus scatter-hoarding rodents appear to be the main dispersal agents. Western juniper cones were eaten by frugivores, and scatter-hoarding is a complimentary or secondary form of seed dispersal. Our results support the notion that Utah juniper has adapted to xeric environments by conserving water through the loss of fleshy fruits that attract frugivores and instead relies on scatter-hoarding rodents as effective dispersal agents.

  4. Evaluating the potential for weed seed dispersal based on waterfowl consumption and seed viability.

    Science.gov (United States)

    Farmer, Jaime A; Webb, Elisabeth B; Pierce, Robert A; Bradley, Kevin W

    2017-12-01

    Migratory waterfowl have often been implicated in the movement of troublesome agronomic and wetland weed species. However, minimal research has been conducted to investigate the dispersal of agronomically important weed species by waterfowl. The two objectives for this project were to determine what weed species are being consumed by ducks and snow geese, and to determine the recovery rate and viability of 13 agronomic weed species after passage through a duck's digestive system. Seed recovered from digestive tracts of 526 ducks and geese harvested during a 2-year field study had 35 020 plants emerge. A greater variety of plant species emerged from ducks each year (47 and 31 species) compared to geese (11 and 3 species). Viable seed from 11 of 13 weed species fed to ducks in a controlled feeding study were recovered. Viability rate and gut retention times indicated potential dispersal up to 2900 km from the source depending on seed characteristics and variability in waterfowl dispersal distances. Study results confirm that waterfowl are consuming seeds from a variety of agronomically important weed species, including Palmer amaranth, which can remain viable after passage through digestive tracts and have potential to be dispersed over long distances by waterfowl. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  5. Seed dispersal into wetlands: Techniques and results for a restored tidal freshwater marsh

    Science.gov (United States)

    Neff, K.P.; Baldwin, A.H.

    2005-01-01

    Although seed dispersal is assumed to be a major factor determining plant community development in restored wetlands, little research exists on density and species richness of seed available through dispersal in these systems. We measured composition and seed dispersal rates at a restored tidal freshwater marsh in Washington, DC, USA by collecting seed dispersing through water and wind. Seed dispersal by water was measured using two methods of seed collection: (1) stationary traps composed of coconut fiber mat along an elevation gradient bracketing the tidal range and (2) a floating surface trawl net attached to a boat. To estimate wind dispersal rates, we collected seed from stationary traps composed of coconut fiber mat positioned above marsh vegetation. We also collected a small number of samples of debris deposited along high tide lines (drift lines) and feces of Canada Goose to explore their seed content. We used the seedling emergence method to determine seed density in all samples, which involved placing the fiber mats or sample material on top of potting soil in a greenhouse misting room and enumerating emerging seedlings. Seedlings from a total of 125 plant species emerged during this study (including 82 in river trawls, 89 in stationary water traps, 21 in drift lines, 39 in wind traps, and 10 in goose feces). The most abundant taxa included Bidens frondosa, Boehmeria cylindrica, Cyperus spp., Eclipta prostrata, and Ludwigia palustris. Total seedling density was significantly greater for the stationary water traps (212 + 30.6 seeds/m2/month) than the equal-sized stationary wind traps (18 + 6.0 seeds/m(2)/month). Lower-bound estimates of total species richness based on the non-parametric Chao 2 asymptotic estimators were greater for seeds in water (106 + 1.4 for stationary water traps and 104 + 5.5 for trawl samples) than for wind (54 + 6.4). Our results indicate that water is the primary source of seeds dispersing to the site and that a species-rich pool

  6. Refaunation and the reinstatement of the seed-dispersal function in Gorongosa National Park.

    Science.gov (United States)

    Correia, Marta; Timóteo, Sérgio; Rodríguez-Echeverría, Susana; Mazars-Simon, Alban; Heleno, Ruben

    2017-02-01

    Large animals are important seed dispersers; however, they tend to be under a high extinction risk worldwide. There is compelling evidence that the global biodiversity crisis is leading to the deterioration of several ecosystem functions, but there is virtually no information on how large-scale refaunation efforts can reinstate seed dispersal. We evaluated the effectiveness of a 62-km 2 wildlife sanctuary, which was established to recover populations of large mammals in Gorongosa National Park (Mozambique), in restoring seed dispersal. We collected animal scats during the dry season of 2014 (June-August) along 5 transects inside and 5 transects outside the sanctuary fence (50 km total) with the same type of plant community, identified animal and plant species in the transects, and quantified the number of seeds in each scat. Based on these data, we built bipartite networks and calculated network and species-level descriptor values, and we compared data collected inside and outside the sanctuary. There were more scats (268 vs. 207) and more scats containing seeds (132 vs. 94) inside than outside the sanctuary. The number of mammal dispersers was also higher inside (17) than outside the sanctuary (11). Similarly, more seeds (2413 vs. 2124) and plant species (33 vs. 26) were dispersed inside than outside the sanctuary. Overall, the seed-dispersal network was less specialized (0.38 vs. 0.44) and there was a greater overlap (0.16 vs. 0.07) inside than outside the sanctuary. Both networks were significantly modular and antinested. The high number and richness of seeds dispersed inside the sanctuary was explained mostly by a higher abundance of dispersers rather than by disperser identity. Our results suggest conservation efforts aimed at recovering populations of large mammals are helping to reestablish not only target mammal species but also their functional roles as seed dispersers in the ecosystem. © 2016 Society for Conservation Biology.

  7. Emergence of ratio-dependent and predator-dependent functional responses for pollination mutualism and seed parasitism

    Science.gov (United States)

    DeAngelis, Donald L.; Holland, J. Nathaniel

    2006-01-01

    Prey (N) dependence [g(N)], predator (P) dependence [g(P) or g(N,P)], and ratio dependence [f(P/N)] are often seen as contrasting forms of the predator's functional response describing predator consumption rates on prey resources in predator–prey and parasitoid–host interactions. Analogously, prey-, predator-, and ratio-dependent functional responses are apparently alternative functional responses for other types of consumer–resource interactions. These include, for example, the fraction of flowers pollinated or seeds parasitized in pollination (pre-dispersal) seed-parasitism mutualisms, such as those between fig wasps and fig trees or yucca moths and yucca plants. Here we examine the appropriate functional responses for how the fraction of flowers pollinated and seeds parasitized vary with the density of pollinators (predator dependence) or the ratio of pollinator and flower densities (ratio dependence). We show that both types of functional responses can emerge from minor, but biologically important variations on a single model. An individual-based model was first used to describe plant–pollinator interactions. Conditional upon on whether the number of flowers visited by the pollinator was limited by factors other than search time (e.g., by the number of eggs it had to lay, if it was also a seed parasite), and on whether the pollinator could directly find flowers on a plant, or had to search, the simulation results lead to either a predator-dependent or a ratio-dependent functional response. An analytic model was then used to show mathematically how these two cases can arise.

  8. Reconstructing past ecological networks: the reconfiguration of seed-dispersal interactions after megafaunal extinction.

    Science.gov (United States)

    Pires, Mathias M; Galetti, Mauro; Donatti, Camila I; Pizo, Marco A; Dirzo, Rodolfo; Guimarães, Paulo R

    2014-08-01

    The late Quaternary megafaunal extinction impacted ecological communities worldwide, and affected key ecological processes such as seed dispersal. The traits of several species of large-seeded plants are thought to have evolved in response to interactions with extinct megafauna, but how these extinctions affected the organization of interactions in seed-dispersal systems is poorly understood. Here, we combined ecological and paleontological data and network analyses to investigate how the structure of a species-rich seed-dispersal network could have changed from the Pleistocene to the present and examine the possible consequences of such changes. Our results indicate that the seed-dispersal network was organized into modules across the different time periods but has been reconfigured in different ways over time. The episode of megafaunal extinction and the arrival of humans changed how seed dispersers were distributed among network modules. However, the recent introduction of livestock into the seed-dispersal system partially restored the original network organization by strengthening the modular configuration. Moreover, after megafaunal extinctions, introduced species and some smaller native mammals became key components for the structure of the seed-dispersal network. We hypothesize that such changes in network structure affected both animal and plant assemblages, potentially contributing to the shaping of modern ecological communities. The ongoing extinction of key large vertebrates will lead to a variety of context-dependent rearranged ecological networks, most certainly affecting ecological and evolutionary processes.

  9. The Effect of Height, Wing Length, and Wing Symmetry on Tabebuia rosea Seed Dispersal

    Directory of Open Access Journals (Sweden)

    Yasmeen Moussa

    2014-12-01

    Full Text Available The relationship between the vertical drop height and the horizontal distance traveled (dispersal ratio was investigated for a sample of fifty Tabebuia rosea seeds by dropping the seeds from five heights ranging from 1.00 to 2.00 meters. The dispersal ratio was found to be a constant 0.16 m/m for these heights. The effects of total seed length and asymmetry of seed wings on dispersal ratio were also measured using separate samples of fifty Tabebuia rosea seeds. It was found that neither seed length nor asymmetry had a significant effect on the dispersal ratio.

  10. On the relative contributions of wind vs. animals to seed dispersal of four Sierra Nevada pines.

    Science.gov (United States)

    Vander Wall, Stephen B

    2008-07-01

    Selective pressures that influence the form of seed dispersal syndromes are poorly understood. Morphology of plant propagules is often used to infer the means of dispersal, but morphology can be misleading. Several species of pines, for example, have winged seeds adapted for wind dispersal but owe much of their establishment to scatter-hoarding animals. Here the relative importance of wind vs. animal dispersal is assessed for four species of pines of the eastern Sierra Nevada that have winged seeds but differed in seed size: lodgepole pine (Pinus contorta murrayana, 8 mg); ponderosa pine (Pinus ponderosa ponderosa, 56 mg); Jeffrey pine (Pinus jeffreyi, 160 mg); and sugar pine (Pinus lambertiana, 231 mg). Pre-dispersal seed mortality eliminated much of the ponderosa pine seed crop (66%), but had much less effect on Jeffrey pine (32% of seeds destroyed), lodgepole pine (29%), and sugar pine (7%). When cones opened most filled seeds were dispersed by wind. Animals removed > 99% of wind-dispersed Jeffrey and sugar pine seeds from the ground within 60 days, but animals gathered only 93% of lodgepole pine seeds and 38% of ponderosa pine seeds during the same period. Animals gathered and scatter hoarded radioactively labeled ponderosa, Jeffrey, and sugar pine seeds, making a total of 2103 caches over three years of study. Only three lodgepole pine caches were found. Caches typically contained 1-4 seeds buried 5-20 mm deep, depths suitable for seedling emergence. Although Jeffrey and sugar pine seeds are initially wind dispersed, nearly all seedlings arise from animal caches. Lodgepole pine is almost exclusively wind dispersed, with animals acting as seed predators. Animals treated ponderosa pine in an intermediate fashion. Two-phased dispersal of large, winged pine seeds appears adaptive; initial wind dispersal helps to minimize pre-dispersal seed mortality whereas scatter hoarding by animals places seeds in sites with a higher probability of seedling establishment.

  11. Complementary roles of two resilient neotropical mammalian seed dispersers

    Science.gov (United States)

    de Almeida, Adriana; Morris, Rebecca J.; Lewis, Owen T.; Mikich, Sandra B.

    2018-04-01

    Capuchin monkeys (Cebus spp. and Sapajus spp.) and coatis (Nasua spp.) coexist in most neotropical forests, including small forest remnants. Both capuchins and coatis eat fruit and disperse seeds, but little is known about whether their roles in seed dispersal are redundant or complementary. We compiled 49 studies from the literature on feeding by capuchins and/or coatis, of which 19 were comprehensive enough for our analyses. We determined the relative importance of fruit eating to each species and compared their diets. Additionally, we analysed the structure of three fruit-frugivore networks built with both animal groups and the fruits they eat and evaluated whether fruit traits influenced the network topology. Fruits represented the largest part of capuchin and coati diets, even though coatis have been known for their opportunistic and generalist diets. Capuchins and coatis also exhibited similar general diet parameters (niche breadth and trophic diversity). The three networks exhibited high connectance values and variable niche overlap. A Multiple Correspondence Analysis, failed to detect any trait or trait combination related to food use. In conclusion, capuchins and coatis both have generalist diets; they feed on many different species of fruits and exhibit important complementarity as seed dispersers. Both are likely to be particularly important seed dispersers in disturbed and fragmented forests.

  12. Long-distance seed dispersal by straw-coloured fruit bats varies by season and landscape

    Directory of Open Access Journals (Sweden)

    Michael Abedi-Lartey

    2016-07-01

    Full Text Available On-going fragmentation of tropical forest ecosystems and associated depletion of seed dispersers threatens the long-term survival of animal-dispersed plants. These threats do not only affect biodiversity and species abundance, but ultimately ecosystem functions and services. Thus, seed dispersers such as the straw-coloured fruit bat, E. helvum, which traverse long distances across fragmented landscapes, are particularly important for maintaining genetic connectivity and colonizing new sites for plant species. Using high-resolution GPS-tracking of movements, field observations and gut retention experiments, we quantify dispersal distances for small- and large-seeded fruits foraged by E. helvum during periods of colony population low (wet season and high (dry season in an urban and a rural landscape in the forest zone of Ghana. Gut passage time averaged 116 min (range 4–1143 min, comparable to other fruit bats. Movements were generally longer in the urban than in the rural landscape and also longer in the dry than in the wet season. As the majority of seeds are dispersed only to feeding roosts, median dispersal distances were similar for both large (42–67 m and small (42–65 m seeds. However, small seeds were potentially dispersed up to 75.4 km, four times further than the previous maximum distance estimated for a similar-sized frugivore. Maximum seed dispersal distances for small seeds were almost twice as long in the rural (49.7 km compare to the urban (31.2 km landscape. Within the urban landscape, estimated maximum dispersal distances for small seeds were three times longer during the dry season (75.4 km compared to the wet season (22.8 km; in contrast, distances in the rural landscape were three times longer in the wet season (67 km compared to the dry season (24.4. Dispersal distances for large seeds during the dry season (551 m in the rural landscape were almost twice that in the wet season (319 m. We found no influence of food

  13. Can salvage logging affect seed dispersal by birds into burned forests?

    Science.gov (United States)

    Rost, J.; Pons, P.; Bas, J. M.

    2009-09-01

    The recovery of vegetation in Mediterranean ecosystems after wildfire is mostly a result of direct regeneration, since the same species existing before the fire regenerate on-site by seeding or resprouting. However, the possibility of plant colonization by dispersal of seeds from unburned areas remains poorly studied. We addressed the role of the frugivorous, bird-dependent seed dispersal (seed rain) of fleshy-fruited plants in a burned and managed forest in the second winter after a fire, before on-site fruit production had begun. We also assessed the effect on seed rain of different microhabitats resulting from salvage logging (erosion barriers, standing snags, open areas), as well as the microhabitats of unlogged patches and an unburned control forest, taking account of the importance of perches as seed rain sites. We found considerable seed rain by birds in the burned area. Seeds, mostly from Olive trees Olea europaea and Evergreen pistaches Pistacia lentiscus, belonged to plants fruiting only in surrounding unburned areas. Seed rain was heterogeneous, and depended on microhabitat, with the highest seed density in the unburned control forest but closely followed by the wood piles of erosion barriers. In contrast, very low densities were found under perches of standing snags. Furthermore, frugivorous bird richness seemed to be higher in the erosion barriers than elsewhere. Our results highlight the importance of this specific post-fire management in bird-dependent seed rain and also may suggest a consequent heterogeneous distribution of fleshy-fruited plants in burned and managed areas. However, there needs to be more study of the establishment success of dispersed seeds before an accurate assessment can be made of the role of bird-mediated seed dispersal in post-fire regeneration.

  14. The evolution of plant-insect mutualisms.

    Science.gov (United States)

    Bronstein, Judith L; Alarcón, Ruben; Geber, Monica

    2006-01-01

    Mutualisms (cooperative interactions between species) have had a central role in the generation and maintenance of life on earth. Insects and plants are involved in diverse forms of mutualism. Here we review evolutionary features of three prominent insect-plant mutualisms: pollination, protection and seed dispersal. We focus on addressing five central phenomena: evolutionary origins and maintenance of mutualism; the evolution of mutualistic traits; the evolution of specialization and generalization; coevolutionary processes; and the existence of cheating. Several features uniting very diverse insect-plant mutualisms are identified and their evolutionary implications are discussed: the involvement of one mobile and one sedentary partner; natural selection on plant rewards; the existence of a continuum from specialization to generalization; and the ubiquity of cheating, particularly on the part of insects. Plant-insect mutualisms have apparently both arisen and been lost repeatedly. Many adaptive hypotheses have been proposed to explain these transitions, and it is unlikely that any one of them dominates across interactions differing so widely in natural history. Evolutionary theory has a potentially important, but as yet largely unfilled, role to play in explaining the origins, maintenance, breakdown and evolution of insect-plant mutualisms.

  15. Interactions between seed traits and digestive processes determine the germinability of bird-dispersed seeds

    NARCIS (Netherlands)

    Kleyheeg, Erik; Claessens, Mascha; Soons, Merel B.

    2018-01-01

    Waterbirds disperse a wide range of plant seeds via their guts, promoting biotic connectivity between isolated habitat patches. However, the intensity of digestive forces encountered by seeds, and therefore their potential to survive digestive tract passage, varies within and between waterbird

  16. Seed production, seed dispersal and seedling establishment of two afromontane tree species in and around a church forest: implications for forest restoration

    Directory of Open Access Journals (Sweden)

    Abrham Abiyu

    2016-07-01

    Full Text Available Background Seed production, seed dispersal and seedling establishment are relevant life phases of plants. Understanding these processes and their patterns is essential to recognize vegetation dynamics and to apply it to forest restoration. Methods For Olea europaea and Schefflera abyssinica, fecundity was estimated using randomized branch sampling. Seed dispersal and seedling establishment were monitored using spatially explicit seed traps and plots. Dispersal functions were calibrated applying inverse modeling. Results O. europaea produced more seeds and had longer dispersal distances compared to S. abyssinica. Correlations between observed and predicted number of recruits were statistically significant. Seedlings of the two species showed different niche requirements. Conclusions The studied species were recruitment-limited due to low dispersal activity or lack of suitable microsites. Restoration relying on natural regeneration should overcome these limitations by increasing disperser visitation and reducing biotic and abiotic stresses.

  17. Seed Dispersal Anachronisms: Rethinking the Fruits Extinct Megafauna Ate

    OpenAIRE

    Guimarães, Paulo R.; Galetti, Mauro; Jordano, Pedro

    2008-01-01

    Background: Some neotropical, fleshy-fruited plants have fruits structurally similar to paleotropical fruits dispersed by megafauna (mammals .103 kg), yet these dispersers were extinct in South America 10–15 Kyr BP. Anachronic dispersal systems are best explained by interactions with extinct animals and show impaired dispersal resulting in altered seed dispersal dynamics. Methodology/Principal Findings: We introduce an operational definition of megafaunal fruits and perform a comparativ...

  18. Galápagos land iguana (Conolophus subcristatus) as a seed disperser.

    Science.gov (United States)

    Traveset, Anna; Nogales, Manuel; Vargas, Pablo; Rumeu, Beatriz; Olesen, Jens M; Jaramillo, Patricia; Heleno, Ruben

    2016-05-01

    The role of the most common land iguana (Conolophus subcristatus) in the Galápagos Islands as an effective seed disperser is explored in this study. A total of 5705 seeds of 32 plant species were identified from 160 scats, 4545 of which (80%) appeared visually undamaged. Germination trials of 849 seeds from 29 species revealed that at least 10 species remained viable after passing through the iguana's gut, although only a small proportion of those seeds (4%) germinated. In any case, we argue that C. subcristatus exerts an important role on the 7 Galapagos islands where it occurs because of its abundance and capacity to ingest and disperse seeds at long distances. Our results strongly suggest that the Galápagos C. subcristatus plays an important role as a seed disperser of not only of native species but also some introduced plants in the Galápagos Islands. © 2016 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

  19. High Resilience of Seed Dispersal Webs Highlighted by the Experimental Removal of the Dominant Disperser.

    Science.gov (United States)

    Timóteo, Sérgio; Ramos, Jaime Albino; Vaughan, Ian Phillip; Memmott, Jane

    2016-04-04

    The pressing need to conserve and restore habitats in the face of ongoing species loss [1, 2] requires a better understanding of what happens to communities when species are lost or reinstated [3, 4]. Theoretical models show that communities are relatively insensitive to species loss [5, 6]; however, they disagree with field manipulations showing a cascade of extinctions [7, 8] and have seldom been tested under field conditions (e.g., [9]). We experimentally removed the most abundant seed-dispersing ant species from seed dispersal networks in a Mediterranean landscape, replicating the experiment in three types of habitat, and then compared these communities to un-manipulated control communities. Removal did not result in large-scale changes in network structure. It revealed extensive structural plasticity of the remaining community, which rearranged itself through rewiring, while maintaining its functionality. The remaining ant species widened their diet breadth in a way that maintained seed dispersal, despite the identity of many interactions changing. The species interaction strength decreased; thus, the importance of each ant species for seed dispersal became more homogeneous, thereby reducing the dependence of seed species on one dominant ant species. Compared to the experimental results, a simulation model that included rewiring considerably overestimated the effect of species loss on network robustness. If community-level species loss models are to be of practical use in ecology or conservation, they need to include behavioral and population responses, and they need to be routinely tested under field conditions; doing this would be to the advantage of both empiricists and theoreticians. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Seed dispersal increases local species richness and reduces spatial turnover of tropical tree seedlings.

    Science.gov (United States)

    Wandrag, Elizabeth M; Dunham, Amy E; Duncan, Richard P; Rogers, Haldre S

    2017-10-03

    Dispersal is thought to be a key process underlying the high spatial diversity of tropical forests. Just how important dispersal is in structuring plant communities is nevertheless an open question because it is very difficult to isolate dispersal from other processes, and thereby measure its effect. Using a unique situation, the loss of vertebrate seed dispersers on the island of Guam and their presence on the neighboring islands of Saipan and Rota, we quantify the contribution of vertebrate seed dispersal to spatial patterns of diversity of tree seedlings in treefall gaps. The presence of vertebrate seed dispersers approximately doubled seedling species richness within canopy gaps and halved species turnover among gaps. Our study demonstrates that dispersal plays a key role in maintaining local and regional patterns of diversity, and highlights the potential for ongoing declines in vertebrate seed dispersers to profoundly alter tropical forest composition.

  1. Overseas seed dispersal by migratory birds.

    Science.gov (United States)

    Viana, Duarte S; Gangoso, Laura; Bouten, Willem; Figuerola, Jordi

    2016-01-13

    Long-distance dispersal (LDD) promotes the colonization of isolated and remote habitats, and thus it has been proposed as a mechanism for explaining the distributions of many species. Birds are key LDD vectors for many sessile organisms such as plants, yet LDD beyond local and regional scales has never been directly observed nor quantified. By sampling birds caught while in migratory flight by GPS-tracked wild falcons, we show that migratory birds transport seeds over hundreds of kilometres and mediate dispersal from mainland to oceanic islands. Up to 1.2% of birds that reached a small island of the Canary Archipelago (Alegranza) during their migration from Europe to Sub-Saharan Africa carried seeds in their guts. The billions of birds making seasonal migrations each year may then transport millions of seeds. None of the plant species transported by the birds occurs in Alegranza and most do not occur on nearby Canary Islands, providing a direct example of the importance of environmental filters in hampering successful colonization by immigrant species. The constant propagule pressure generated by these LDD events might, nevertheless, explain the colonization of some islands. Hence, migratory birds can mediate rapid range expansion or shifts of many plant taxa and determine their distribution. © 2016 The Author(s).

  2. [Role of mammals on seed dispersal and predation processes of Mauritia flexuosa (Arecaceae)

    Science.gov (United States)

    Acevedo-Quintero, Juan Fernando; Zamora-Abrego, Joan Gastón

    2016-03-01

    Mammals and palms are important elements of fauna and flora in the Neotropics, and their interactions, such as fruit consumption and seed dispersal, are one of the most important ecological relationships in these ecosystems. The main objective of this study was to identify the relative importance of mammals in the dispersal and predation of Mauritia flexuosa palm fruits. We installed camera-traps in front of palm fallen seeds and clusters with fruits. A catalog of species was prepared with the recorded videos and the foraging behaviors exhibited were classified and identified. In addition, two exclusion treatments with three repetitions each were used. In the semi-open treatment, a plot was fenced with metal mesh leaving four open- ings in order to allow access only to small and medium sized mammals, while in the open treatment, the small, medium and large sized mammals had free access. In both cases, seed removal was evaluated. We recorded a total of 19 species of mammals, nine of which fed on palm fruits and the other five were seed dispersers. We reported for the first time the consumption of Mauritia flexuosa fruits by Atelocynus microtis. The species with the highest relative importance was Dasyprocta fuliginosa, which showed the highest percentage of seed dispersal (63.5%) compared to the other species. Tayassu peccary was identified as an in situ consumer, eating 45.3% of seeds without dispersing them. The number of seeds consumed in situ in the open treatment showed significant differences regarding the semi-open treatment, suggesting greater involvement of large mammals in this process. In conclusion, the fruits of M. flexuosa are an important food source for the local mammal com- munity. Additionally, the consumption of seeds under the canopy of the mother palm is proportionally greater than their dispersion. Generally, the pressure of frugivorous species over seeds may determine the reproductive strategies of plants. However, research on effective

  3. Complementing endozoochorous seed dispersal patterns by donkeys and goats in a semi-natural island ecosystem.

    Science.gov (United States)

    Treitler, Julia Tabea; Drissen, Tim; Stadtmann, Robin; Zerbe, Stefan; Mantilla-Contreras, Jasmin

    2017-12-19

    Endozoochory is, in grazing systems, a substantial vector for seed dispersal. It can play an important role in vegetation dynamics, especially in colonization processes through seed input on the vegetation and on the soil seed bank. We investigated the endozoochorous seed input of donkeys and goats on a semi-natural island ecosystem in the Mediterranean. Through germination experiments, we assessed the viable seed content of the dung of these grazing animals to estimate their suitability and efficiency for seed dispersal of the vegetation types of the island. We show different dispersal patterns of donkeys and goats. Goats disperse a high number of diaspores from shrubs while donkeys disperse more diaspores of grasses. In addition, goats disperse plants of greater growth height and donkeys plants of shorter height. These dispersal patterns are in accordance with the vegetation types of which donkeys and goats disperse indicator species. Both, donkeys and goats, feed on and disperse species of the vegetation types, open grassland and temporarily wet grassland. In addition, goats feed on and disperse diagnostic species of the semi-open maquis and preforest formations. Overall, our results show that donkeys and goats are complementing each other in their endozoochorous seed dispersal potential. This emphasizes the importance of both grazing animals for the vegetation dynamics of the semi-natural island ecosystem. Therefore, the adaption of the goat management to a traditional land management based on directed transhumance might maintain and enrich vegetation types.

  4. Locomotion during digestion changes current estimates of seed dispersal kernels by fish

    NARCIS (Netherlands)

    Leeuwen, van C.H.A.; Beukeboom, R.; Nolet, B.A.; Bakker, E.S.; Pollux, B.J.A.

    2016-01-01

    1.Dispersal of seeds by animals is an important mechanism regulating plant diversity, range expansions and invasions. Many birds, mammals, fish and reptiles regularly ingest, transport and excrete viable seeds (known as endozoochory). 2.The effectiveness of endozoochory is modelled in dispersal

  5. Seed dispersal and predation of Buchenavia tomentosa Eichler (Combretaceae in a Cerrado sensu stricto, midwest Brazil

    Directory of Open Access Journals (Sweden)

    J. Farias

    Full Text Available Abstract The ecology of seed dispersal is critical to understand the patterns of distribution and abundance of plant species. We investigated seed dispersal aspects associated with the high abundance of Buchenavia tomentosa in the Serra Azul State Park (PESA. We estimated fruit production and conducted fruit removal experiments. We carried out diurnal and nocturnal observations on frugivory as well as germination tests. Fruiting occurred in the dry season and totaled 1,365,015 ± 762,670 fruits.ha–1. B. tomentosa fruits were utilized by eight animal species. The lowland tapir (Tapirus terrestris was considered the main seed disperser. Leafcutter ants (Atta laevigata and Atta sexdens participated in the seed cleaning and occasionally dispersed seeds. The beetle Amblycerus insuturatus, blue-and-yellow macaw (Ara ararauna and red-and-green macaw (Ara chloropterus were considered pre-dispersal seed predators. The seeds manually cleaned presented higher germination rate (100% and speed index (4.2 seeds.d–1 than that of seeds with pulp. Germination of seeds found in tapirs’feces was 40%, while for the seeds without pulp it was 25%. The high abundance of B. tomentosa in the cerrado of PESA may be due to massive fruit production, low rates of seed predation, and efficient seed dispersal by tapirs, occurring before the rains which promote germination and recruitment of this species.

  6. Potential effects of arboreal and terrestrial avian dispersers on seed dormancy, seed germination and seedling establishment in Ormosia (Papilionoideae) species in Peru

    Science.gov (United States)

    Foster, Mercedes S.

    2008-01-01

    The relative effectiveness of arboreal or terrestrial birds at dispersing seeds of Ormosia macrocalyx and O. bopiensis (Fabaceae: Papilionoideae) were studied in south-eastern Peru. Seeds of both species were either scarified, to represent seed condition after dispersal by terrestrial birds, or left intact, to represent seed condition after dispersal by arboreal birds. Seeds were distributed along forest transects, and germination, seedling development and mortality were monitored to determine the successes of the two groups at producing seedlings. Scarified seeds germinated with the early rains of the dry-to-wet-season transition, when erratic rainfall was interspersed with long dry spells. Intact seeds germinated 30 d later when the rain was more plentiful and regular. Intact seeds of O. macrocalyx gave rise to significantly more seedlings (41.1% vs. 25.5%) than did scarified seeds, in part, because significantly more seedlings from scarified seeds (n = 20) than from intact seeds (n = 3) died from desiccation when their radicles failed to enter the dry ground present during the dry-to-wet-season transition. Also, seedlings from scarified seeds were neither larger nor more robust than those from intact seeds despite their longer growing period. Results are consistent with the hypothesis that dispersal effectiveness of arboreal birds, at least for O. macrocalyx, is greater than that of terrestrial birds. Screen-house experiments in which seedlings developed under different watering regimes supported this result. Numbers of seedlings developing from intact and scarified seeds of O. bopiensis did not differ significantly.

  7. Locomotion during digestion changes current estimates of seed dispersal kernels by fish

    NARCIS (Netherlands)

    van Leeuwen, Casper H.A.; Beukeboom, Rosanne; Nolet, Bart A.; Bakker, Elisabeth S.; Pollux, Bart J.A.

    2016-01-01

    Dispersal of seeds by animals is an important mechanism regulating plant diversity, range expansions and invasions. Many birds, mammals, fish, and reptiles regularly ingest, transport and excrete viable seeds (known as endozoochory). The effectiveness of endozoochory is modelled in dispersal

  8. Habitat differences in dung beetle assemblages in an African savanna-forest ecotone: implications for secondary seed dispersal.

    Science.gov (United States)

    Kunz, Britta K; Krell, Frank-Thorsten

    2011-06-01

    The probability and pattern of secondary seed dispersal by dung beetles (Scarabaeinae) depend on their community structure and composition at the site of primary deposition, which, in turn, seem to be strongly determined by vegetation. Consequently, we expected pronounced differences in secondary seed dispersal between forest and savanna in the northern Ivory Coast, West Africa. We found 99 dung beetle species at experimentally exposed dung piles of the olive baboon (Papio anubis (Lesson, 1827)), an important primary seed disperser in West Africa. Seventy-six species belonged to the roller and tunneler guilds, which are relevant for secondary seed dispersal. Most species showed a clear habitat preference. Contrary to the Neotropics, species number and abundance were much higher in the savanna than in the forest. Rollers and tunnelers each accounted for approximately 50% of the individuals in the savanna, but in the forest rollers made up only 4%. Seeds deposited into the savanna by an omnivorous primary disperser generally have a higher overall probability of being more rapidly dispersed secondarily by dung beetles than seeds in the forest. Also, rollers disperse seeds over larger distances. In contrast to other studies, small rollers were active in dispersal of large seeds, which were seemingly mistaken for dung balls. Our results suggest that rollers can remove seeds from any plant dispersed in primate dung in this ecosystem. © 2011 ISZS, Blackwell Publishing and IOZ/CAS.

  9. Estimating adhesive seed-dispersal distances : field experiments and correlated random walks

    NARCIS (Netherlands)

    Mouissie, AM; Lengkeek, W; van Diggelen, R

    1. In this study we aimed to estimate distance distributions of adhesively dispersed seeds and the factors that determine them. 2. Seed attachment and detachment were studied using field experiments with a real sheep, a sheep dummy and a cattle dummy. Seed-retention data were used in correlated

  10. Frugivores and seed dispersal: mechanisms and consequences for biodiversity of a key ecological interaction.

    Science.gov (United States)

    Jordano, Pedro; Forget, Pierre-Michel; Lambert, Joanna E; Böhning-Gaese, Katrin; Traveset, Anna; Wright, S Joseph

    2011-06-23

    The 5th Symposium on Frugivores and Seed Dispersal, held in Montpellier (France), 13-18 June 2010, brought together more than 220 researchers exemplifying a wide diversity of approaches to the study of frugivory and dispersal of seeds. Following Ted Fleming and Alejandro Estrada's initiative in 1985, this event was a celebration of the 25th anniversary of the first meeting in Veracruz, Mexico. Frugivory and seed dispersal are active research areas that have diversified in multiple directions since 1985 to include evolution (e.g. phylogenetic diversity and dispersal adaptations), physiology (e.g. sensory cues and digestion), landscape ecology (movement patterns), molecular ecology (e.g. gene flow, genetic diversity and structure), community ecology (e.g. mutualistic interaction networks) and conservation biology (effects of hunting, fragmentation, invasion and extinction), among others. This meeting provided an opportunity to assess conceptual and methodological progress, to present ever more sophisticated insights into frugivory in animals and dispersal patterns in plants, and to report the advances made in examining the mechanisms and consequences of seed dispersal for plants and frugivores.

  11. Field experiments on seed dispersal by wind in ten umbelliferous species (Apiaceae)

    NARCIS (Netherlands)

    Jongejans, E.; Telenius, A.

    2001-01-01

    This report presents data from experiments on seed dispersal by wind for ten species of the family Apiaceae. Seed shadows were obtained in the field under natural conditions, using wind speeds between four and ten m/s. The flight of individual seeds was followed by eye, and seed shadows were

  12. Spatial heterogeneity in post-dispersal predation on Prunus and Uvularia seeds.

    Science.gov (United States)

    Webb, Sara L; Willson, Mary F

    1985-08-01

    We investigated effects of seed density, distance from parent, and habitat (woods, open field) on post-dispersal predation risk (chiefly by rodents) for seeds of Prunus virginiana (Rosaceae). Additional study of the habitat effect (woods, open field, treefall gap) was made with seeds of Prunus avium (Rosaceae) and Uvularia grandiflora (Liliaceae). Density of Prunus seeds (range 2-40 seeds/group) did not affect predation risk for individual seeds. Distance from parent plants did influence predation risk, which was greatest directly beneath parents. This distance effect primarily comprised a sharp drop in risk within 2 m of parents, a distance too small to generate a "spacing rule" for conspecifics.We found that habitat strongly influenced predation intensity. Rates of removal of Prunus seeds were higher in woods than in open fields, except when overall predation intensity was very low and no pattern could be discerned. Prunus seed removal rates were higher in closed woods than in treefall gaps. Consequently, a Prunus seed will more likely escape predation if dispersed to an open site. In contrast, Uvularia seed removal rates were higher in open fields than in woods but did not differ between closed woods and tree-fall gaps.Predation intensity was spatially patchy between and within experimental arrays, but was consistent over time at some specific points in space, possibly reflecting home ranges of seed predators.

  13. Genetic consequences of seed dispersal to sleeping trees by white-bellied spider monkeys

    Science.gov (United States)

    Karubian, Jordan; Ottewell, Kym; Link, Andres; Di Fiore, Anthony

    2015-10-01

    Frugivorous animals frequently generate clumped distributions of seeds away from source trees via 'destination-based' dispersal processes. For example, use of traditional sleeping trees by white-bellied spider monkeys Ateles belzebuth generates high densities of seeds of a preferred food source, the palm Oenocarpus bataua, at these sites. Little is known about the maternal seed source diversity and population genetic metrics of seed pools encountered at these sites. Given the repeated use of sleeping trees over time, and the fluid social organization and wide ranging movements exhibited by spider monkeys, we predicted that O. bataua seed pools beneath sleeping trees would be characterized by relatively high values of maternal seed source diversity and standard metrics of genetic diversity. Contrary to these expectations, we found relatively low average maternal seed source diversity beneath each of 6 sleeping trees we studied (weighted mean α = 3.74), but considerable variation in diversity of maternal seed sources between sleeping trees (range = 1.75-10.1) and high heterogeneity in standard genetic diversity measures between sleeping trees. There was no evidence for overlap in maternal seed sources between sleeping tree sites (δ = 1.0), resulting in significant genetic differentiation (Fst = 0.055-0.319) between these sites. Observed variation between sleeping trees could not be explained by the number of individual spider monkeys whose core home ranges included a given tree, nor by distance to a central mineral lick, a focal point of spider monkey activity. These findings suggest that spider monkey seed dispersal to sleeping trees is spatially restricted, perhaps because the animals visit sleeping trees at the end of the day and therefore only disperse O. bataua fruits that they ingest late in the day. These results add to our growing appreciation of the ways frugivore behavior mechanistically shapes seed dispersal outcomes.

  14. Splash-cup plants accelerate raindrops to disperse seeds

    Science.gov (United States)

    Amador, Guillermo J.; Yamada, Yasukuni; McCurley, Matthew; Hu, David L.

    2013-01-01

    The conical flowers of splash-cup plants Chrysosplenium and Mazus catch raindrops opportunistically, exploiting the subsequent splash to disperse their seeds. In this combined experimental and theoretical study, we elucidate their mechanism for maximizing dispersal distance. We fabricate conical plant mimics using three-dimensional printing, and use high-speed video to visualize splash profiles and seed travel distance. Drop impacts that strike the cup off-centre achieve the largest dispersal distances of up to 1 m. Such distances are achieved because splash speeds are three to five times faster than incoming drop speeds, and so faster than the traditionally studied splashes occurring upon horizontal surfaces. This anomalous splash speed is because of the superposition of two components of momentum, one associated with a component of the drop's motion parallel to the splash-cup surface, and the other associated with film spreading induced by impact with the splash-cup. Our model incorporating these effects predicts the observed dispersal distance within 6–18% error. According to our experiments, the optimal cone angle for the splash-cup is 40°, a value consistent with the average of five species of splash-cup plants. This optimal angle arises from the competing effects of velocity amplification and projectile launching angle. PMID:23235266

  15. Seed dispersal networks in the Galápagos and the consequences of alien plant invasions

    DEFF Research Database (Denmark)

    Heleno, R. H.; Olesen, Jens Mogens; Nogales, M.

    2013-01-01

    Alien plants are a growing threat to the Gala´pagos unique biota. We evaluated the impact of alien plants on eight seed dispersal networks from two islands of the archipelago. Nearly 10 000 intact seeds from 58 species were recovered from the droppings of 18 bird and reptile dispersers. The most......, followed by small ground finch, two mockingbirds, the giant tortoise and two insectivorous birds. Most animals dispersed alien seeds, but these formed a relatively small proportion of the interactions. Nevertheless, the integration of aliens was higher in the island that has been invaded for longest......, suggesting a time-lag between alien plant introductions and their impacts on seed dispersal networks. Alien plants become more specialized with advancing invasion, favouring more simplified plant and disperser communities. However, only habitat type significantly affected the overall network structure. Alien...

  16. Partitioning of seed dispersal services between birds and bats in a fragment of the Brazilian Atlantic Forest

    Directory of Open Access Journals (Sweden)

    Raissa Sarmento

    2014-06-01

    Full Text Available Community-level network studies suggest that seed dispersal networks may share some universal properties with other complex systems. However, most of the datasets used so far in those studies have been strongly biased towards temperate birds, including not only dispersers, but also seed predators. Recent evidence from multi-taxon networks suggests that seed dispersal networks are not all alike and may be more complex than previously thought. Here, we used network theory to evaluate seed dispersal in a strongly impacted Atlantic Forest fragment in northeastern Brazil, where bats and birds are the only extant dispersers. We hypothesized that the seed dispersal network should be more modular then nested, and that the dispersers should segregate their services according to dispersal syndromes. Furthermore, we predicted that bat and bird species that are more specialized in frugivory would be more important for maintaining the network structure. The mixed network contained 56 plant species, 12 bat species, and eight bird species, and its structure was more modular (M = 0.58 then nested (NODF = 0.21 compared with another multi-taxon network and 21 single-taxon networks (with either bats or birds. All dispersed fruits had seeds smaller than 9 mm. Bats dispersed mainly green fruits, whereas birds dispersed fruits of various colors. The network contained eight modules: five with birds only, two with bats only, and one mixed. Most dispersers were peripheral, and only specialized frugivores acted as hubs or connectors. Our results strongly support recent studies, suggesting that seed dispersal networks are complex mosaics, where different taxa form separate modules with different properties, which in turn play complementary roles in the maintenance of the associated ecosystem functions and services.

  17. Seed dispersal of Diospyros virginiana in the past and the present: Evidence for a generalist evolutionary strategy.

    Science.gov (United States)

    Rebein, Mimi; Davis, Charli N; Abad, Helena; Stone, Taylor; Del Sol, Jillian; Skinner, Natalie; Moran, Matthew D

    2017-06-01

    Several North American trees are hypothesized to have lost their co-evolved seed disperser during the late-Pleistocene extinction and are therefore considered anachronistic. We tested this hypothesis for the American persimmon ( Diospyros virginiana ) by studying the effects of gut passage of proposed seed dispersers on seedling survival and growth, natural fruiting characteristics, and modern animal consumption patterns. We tested gut passage effects on persimmon seeds using three native living species, the raccoon ( Procyon lotor ), Virginia opossum ( Didelphis virginiana ), and coyote ( Canis latrans ), and two Pleistocene analogs; the Asian elephant ( Elephas maximus ) and alpaca ( Vicugna pacos ). Persimmon seeds excreted by raccoons, coyotes, and elephants survived gut transit. Gut passage did not affect sprouting success, but did tend to decrease time to sprout and increase seedling quality. Under field conditions, persimmon fruits were palatable on the parent tree and on the ground for an equal duration, but most fruits were consumed on the ground. Seven vertebrate species fed upon persimmon fruits, with the white-tailed deer ( Odocoileus virginianus )-a species not capable of dispersing persimmon seeds-comprising over 90% of detections. Conversely, potential living seed dispersers were rarely detected. Our results suggest the American persimmon evolved to attract a variety of seed dispersers and thus is not anachronistic. However, human-induced changes in mammal communities could be affecting successful seed dispersal. We argue that changes in the relative abundance of mammals during the Anthropocene may be modifying seed dispersal patterns, leading to potential changes in forest community composition.

  18. Reduced germination success of temperate grassland seeds sown in dung: consequences for post-dispersal seed fate.

    Science.gov (United States)

    Milotić, T; Hoffmann, M

    2016-11-01

    Endozoochory is one of the main drivers shaping temperate grassland communities by maintaining plant populations of its constituents and enabling plants to colonize new habitats. Successful endozoochorous dispersal implies that seeds not only get consumed and survive the digestive tract but are also able to develop into viable seedlings in a dung environment. We experimentally assessed the germination probability and timing of 15 annual and perennial temperate European grassland species in cattle and horse dung and in different climatic conditions (greenhouse and outdoor conditions). Interspecific variation in germinability and germination timing are found, while life strategy had only an effect on germination timing. We found adverse effects of both cattle and horse dung on the germination characteristics of all tested grassland species, but the effects of cattle dung were more pronounced. In comparison with the control treatment, fewer seeds emerged in dung and more time was needed to germinate. Also, germination metrics clearly differed between the artificial greenhouse and outdoor conditions, with generally a lower germinability in outdoor conditions. According to our results, a large cost seems to be associated with endozoochorous dispersal in this stage of the life cycle, as seed dispersal effectiveness strongly depends on the quality of the deposition site with a lowered survival and germination probability when seeds are deposited in dung. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

  19. Red fox ( Vulpes vulpes L.) favour seed dispersal, germination and seedling survival of Mediterranean Hackberry ( Celtis australis L.)

    Science.gov (United States)

    Juan, Traba; Sagrario, Arrieta; Jesús, Herranz; Cristina, Clamagirand M.

    2006-07-01

    Seeds of the Mediterranean Hackberry Celtis australis are often encountered in fox faeces. In order to evaluate the effect of gut transit on the size of seeds selected, the rates and speed of germination and on the survival of the seedlings, Mediterranean Hackberry seeds from fox faeces were germinated in a greenhouse. The results were compared with those of seeds taken from ripe, uneaten fruits. Fox-dispersed seeds were smaller and lighter than the control ones and had higher (74% vs. 57%) and more rapid germination (74.5 days vs. 99.2 days). Seedlings from fox-dispersed seeds showed significantly greater survival by the end of the study period (74.1% vs. 43.6%) than the control ones. Survival in seedlings from fox-dispersed seeds was related to germination date, late seedlings showing poorer survival. This relationship was not observed away in the control seedlings. Seed mass did not affect seedling survival. Seedling arising from fox-dispersed seeds grew faster than control ones. These results suggest that fox can play a relevant role as seed disperser of Mediterranean Hackberry.

  20. Analysis of plant soil seed banks and seed dispersal vectors: Its potential and limits for forensic investigations.

    Science.gov (United States)

    Šumberová, Kateřina; Ducháček, Michal

    2017-01-01

    Plant seeds exhibit many species-specific traits, thus potentially being especially helpful for forensic investigations. Seeds of a broad range of plant species occur in soil seed banks of various habitats and may become attached in large quantities to moving objects. Although plant seeds are now routinely used as trace evidence in forensic practice, only scant information has been published on this topic in the scientific literature. Thus, the standard methods remain unknown to specialists in such botanical subjects as plant ecology and plant geography. These specialists, if made aware of the forensic uses of seeds, could help in development of new, more sophisticated approaches. We aim to bridge the gap between forensic analysts and botanists. Therefore, we explore the available literature and compare it with our own experiences to reveal both the potential and limits of soil seed bank and seed dispersal analysis in forensic investigations. We demonstrate that habitat-specific and thus relatively rare species are of the greatest forensic value. Overall species composition, in terms of species presence/absence and relative abundance can also provide important information. In particular, the ecological profiles of seeds found on any moving object can help us identify the types of environments through which the object had travelled. We discuss the applicability of this approach to various European environments, with the ability to compare seed samples with georeferenced vegetation databases being particularly promising for forensic investigations. We also explore the forensic limitations of soil seed bank and seed dispersal vector analyses. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  1. Pollination and seed dispersal in the endangered succulent ...

    African Journals Online (AJOL)

    The dwarf succulent euphorbia Euphorbia brevitorta (Euphorbiaceae) is a localized and potentially threatened endemic species with limited distributed across rocky grasslands in central and southern Kenya. The pollination ecology and seed dispersal of E. brevitorta was investigated by direct observation. Euphorbia ...

  2. Post-dispersal seed removal by ground-feeding rodents in tropical peatlands, Central Kalimantan, Indonesia

    Science.gov (United States)

    Blackham, Grace V.; Corlett, Richard T.

    2015-01-01

    Forested tropical peatlands in Southeast Asia are being rapidly converted to agriculture or degraded into non-forest vegetation. Although large areas have been abandoned, there is little evidence for subsequent forest recovery. As part of a study of forest degradation and recovery, we used seed removal experiments and rodent surveys to investigate the potential role of post-dispersal seed predation in limiting the regeneration of woody plants. Two 14-day seed removal trials were done in deforested and forested peatland habitat in Central Kalimantan, Indonesia. Seeds of Nephelium lappaceum, Syzygium muelleri, Artocarpus heterophyllus (all animal-dispersed) and Combretocarpus rotundatus (wind-dispersed) were tested. Significantly more seeds (82.8%) were removed in forest than non-forest (38.1%) and Combretocarpus had the lowest removal in both habitats. Most handled seeds were eaten in situ and little caching was observed. Six species of rodents were captured in forest and five in non-forest. The most trapped taxa were three Maxomys spp. in forest (85.5% of individuals) and Rattus tiomanicus in non-forest (74.8%). Camera traps confirmed that rodents were responsible for seed removal. Seed predation in deforested areas, which have a much lower seed rain than forest, may contribute to the low density and diversity of regenerating forest. PMID:26369444

  3. Post-dispersal seed predation of woody forest species limits recolonization of forest plantations on ex-arable land

    DEFF Research Database (Denmark)

    Bruun, Hans Henrik; Valtinat, Karin; Kollmann, Johannes

    2010-01-01

    be differences in recruitment. The present study addresses post-dispersal seed predation, mainly of woody plants, as the factor limiting the recolonization of young oak plantations in southern Sweden. Our objectives were to investigate differences in dispersal and post-dispersal seed predation between first......, the colonization of forest plantations by native shrubs and trees appears to be habitat-limited; the only exception being Rhamnus catharticus, for which poor dispersal ability may be more important. Post-dispersal seed predation of forest shrubs and trees was marked, especially in relatively small and isolated...... plantations on ex-arable land. There was a high seed predation of Crataegus monogyna, Sorbus aucuparia and Viburnum opulus on ex-arable land, while that of Frangula alnus and Sambucus racemosa was not associated with site placement and land-use history. Seed predation is probably a more important factor...

  4. Frugivory and seed dispersal by birds in Cereus jamacaru DC. ssp. jamacaru (Cactaceae) in the Caatinga of Northeastern Brazil.

    Science.gov (United States)

    Gomes, V G N; Quirino, Z G M; Araujo, H F P

    2014-02-01

    Studies of the dispersal modes of plants aid our understanding of the dynamics of resource and its availability for dispersal agents. The present work sought to characterize the fruiting patterns of the native Caatinga (dryland) cactus Cereus jamacaru, identify its principal dispersers, and evaluate the effects of seed passage through digestive tract of dispersers on its germination. Cereus jamacaru present an annual fruiting pattern and fruiting peaks occurred during June/2009 and February/2010. A total of 135 visits by nine species of resident Caatinga bird species were recorded. The most frequent visiting bird species were Paroaria dominicana and Euphonia chlorotica. Length of bird visits varied from 15 seconds to 4 minutes and seeds removed by birds travelled 10.6 ± 11.2 m until dispersers make the first landing perch, in some cases more than 40 meters away. Germination tests show birds had a high quantity of viable seeds of C. jamacaru in its feces. Seeds that passed through the digestive tract of birds showed a similar germinability of the seeds of the control group. However, the seeds dispersed by birds showed lowest mean germination time related to the control group seeds. This study highlights the potential role of birds as seed dispersers of C. jamacaru, swallowing the whole seeds and defecating intact seeds, accelerating the germination process and transporting seeds away from the mother plant.

  5. Frugivores and seed dispersal: mechanisms and consequences for biodiversity of a key ecological interaction

    OpenAIRE

    Jordano, Pedro; Forget, Pierre-Michel; Lambert, Joanna E.; Böhning-Gaese, Katrin; Traveset, Anna; Wright, S. Joseph

    2010-01-01

    The 5th Symposium on Frugivores and Seed Dis- persal, held in Montpellier (France), 13 – 18 June 2010, brought together more than 220 researchers exemplifying a wide diversity of approaches to the study of frugivory and dispersal of seeds. Fol- lowing Ted Fleming and Alejandro Estrada’s initiative in 1985, this event was a celebration of the 25th anniversary of the first meeting in Veracruz, Mexico. Frugivory and seed dispersal are active research areas that hav...

  6. Genetic diversity of dispersed seeds is highly variable among leks of the long-wattled umbrellabird

    Science.gov (United States)

    Ottewell, Kym; Browne, Luke; Cabrera, Domingo; Olivo, Jorge; Karubian, Jordan

    2018-01-01

    Frugivorous animals frequently generate clumped distributions of seeds away from source trees, but genetic consequences of this phenomenon remain poorly resolved. Seed dispersal of the palm Oenocarpus bataua by long-wattled umbrellabirds Cephalopterus penduliger generates high seed densities in leks (i.e., multi-male display sites), providing a suitable venue to investigate how dispersal by this frugivore may influence seed source diversity and genetic structure at local and landscape levels. We found moderate levels of maternal seed source diversity in primary seed rain across five leks in northwest Ecuador (unweighted mean alpha diversity α = 9.52, weighted mean αr = 3.52), with considerable variation among leks (αr range: 1.81-24.55). Qualitatively similar findings were obtained for allelic diversity and heterozygosity. Higher densities of O. bataua adults around leks were associated with higher values of αr and heterozygosity (non-significant trends) and allelic diversity (significant correlation). Seed source overlap between different leks was not common but did occur at low frequency, providing evidence for long-distance seed dispersal by umbrellabirds into leks. Our findings are consistent with the idea that seed pool diversity within leks may be shaped by the interaction between density of local trees, which can vary considerably between leks, and umbrellabird foraging ecology, particularly a lack of territorial defense of fruiting trees. Taken as a whole, this work adds to our growing appreciation of the ways resource distribution and associated frugivore foraging behaviors mechanistically shape seed dispersal outcomes and the distribution of plant genotypes across the landscape.

  7. Evaluating realized seed dispersal across fragmented tropical landscapes : a two-fold approach using parentage analysis and the neighbourhood model

    NARCIS (Netherlands)

    Ismail, Sascha A.; Ghazoul, Jaboury; Ravikanth, Gudasalamani; Kushalappa, Cheppudira G.; Uma Shaanker, Ramanan; Kettle, Chris J.

    2017-01-01

    Despite the importance of seed dispersal for survival of plant species in fragmented landscapes, data on seed dispersal at landscape scales remain sparse. Effective seed dispersal among fragments determines recolonization and plant species persistence in such landscapes. We present the first

  8. Consequences of intraspecific seed-size variation in Sparganium emersum for dispersal by fish

    NARCIS (Netherlands)

    Pollux, B.J.A.; Ouborg, J.; Van Groenendael, J.M.; Klaassen, M.R.J.

    2007-01-01

    The potential for seed dispersal by fish (ichthyochory) is likely to vary within aquatic plant species, depending on intraspecific variation in phenotypic seed traits. 2. We studied the effect of seed size variation within the unbranched burreed (Sparganium emersum) on the potential for internal

  9. Paleocene wind-dispersed fruits and seeds from Colombia and their implications for early Neotropical rainforests

    Directory of Open Access Journals (Sweden)

    Herrera Fabiany

    2014-12-01

    Full Text Available Extant Neotropical rainforests are well known for their remarkable diversity of fruit and seed types. Biotic agents disperse most of these disseminules, whereas wind dispersal is less common. Although wind-dispersed fruits and seeds are greatly overshadowed in closed rainforests, many important families in the Neotropics (e.g., Bignoniaceae, Fabaceae, Malvaceae, Orchidaceae, Sapindaceae show numerous morphological adaptations for anemochory (i.e. wings, accessory hairs. Most of these living groups have high to moderate levels of plant diversity in the upper levels of the canopy. Little is known about the fossil record of wind-dispersed fruits and seeds in the Neotropics. Six new species of disseminules with varied adaptations for wind dispersal are documented here. These fossils, representing extinct genera of Ulmaceae, Malvaceae, and some uncertain families, indicate that wind-dispersed fruit and seed syndromes were already common in the Neotropics by the Paleocene, coinciding with the early development of multistratal rainforests. Although the major families known to include most of the wind-dispersed disseminules in extant rainforests are still missing from the Paleogene fossil record of South and Central America, the new fossils imply that anemochory was a relatively important product and/or mechanism of plant evolution and diversification in early Neotropical rainforests.

  10. Bird attributes, plant characteristics, and seed dispersal of Pera glabrata (Schott, 1858), (Euphorbiaceae) in a disturbed cerrado area.

    Science.gov (United States)

    Francisco, M R; Lunardi, V O; Galetti, M

    2007-11-01

    Several plant characteristics, such as fruit production, nutrient reward, secondary compounds, and fruit color display, affect fruit choice by birds. On the other hand, several bird attributes affect their efficiency as dispersers. Here we investigate the ornithochoric seed dispersal of Pera glabrata Schott (Euphorbiaceae) in a cerrado fragment in southeastern Brazil. A set of bird attributes, such as frequency of visits, number of diaspores eaten, time spent foraging, methods of taking and handling the diaspores and agonistic interactions were analyzed in order to infer about the potential of each species to act as a seed disperser. Birds were the unique seed dispersers of these oil-rich diaspores. We observed 414 bird visits during 60 hours of focal observations in five trees from December 1999 to January 2000. Twenty bird species from seven families ate the diaspores of P. glabrata, but only 14 species were considered potential seed dispersers because they swallowed the diaspores, increasing the probabilities for the seeds to be defecated and/or regurgitated away from the parent trees. The main potential seed dispersers were: Turdus leucomelas (Muscicapidae), Dacnis cayana (Emberizidae), Colaptes melanochloros (Picidae) and Elaenia spp. (Tyrannidae). We did not find any significant seasonal change in the number of visits on the fruiting trees throughout the day. We also did not find any relation between the number of visits per tree and fruit production. The most effective seed dispersers of P. glabrata were generalist birds, which have a high visiting rate, high fruit consumption rate, and spend short periods on the plants. The large number of species recorded as potential seed dispersers of P. glabrata, being most of them very abundant even in Brazilian disturbed areas, may guarantee seed dispersal of this plant in small fragments and regenerating areas.

  11. Dispersal of invasive Phytolacca americana seeds by birds in an urban garden in China.

    Science.gov (United States)

    Li, Ning; Yang, Wen; Fang, Shubo; Li, Xinhai; Liu, Zhanchen; Leng, Xin; An, Shuqing

    2017-01-01

    Although seed dispersal is a key process determining the regeneration and spread of invasive plant populations, few studies have explicitly addressed the link between dispersal vector behavior and seedling recruitment to gain insight into the invasion process within an urban garden context. We evaluated the role of bird vectors in the dispersal of pokeweed (Phytolacca americana), a North American herb that is invasive in urban gardens in China. Fruiting P. americana attracted both generalist and specialist bird species that fed on and dispersed its seeds. The generalist species Pycnonotus sinensis and Urocissa erythrorhyncha were the most frequent dispersers. Seedling numbers of P. americana were strongly associated with the perching behavior of frugivorous birds. If newly recruited bird species use seedling-safe perching sites, the P. americana will regenerate faster, which would enhance its invasive potential. Based on our observations, we conclude that the 2 main bird vectors, P. sinensis and U. erythrorhyncha, provide potential effective dispersal agents for P. americana. Our results highlight the role of native birds in seed dispersal of invasive plants in urban gardens. © 2016 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

  12. The effect of seed morphology on the potential dispersal of aquatic macrophytes by the common carp (Cyprinus carpio)

    NARCIS (Netherlands)

    Pollux, B.J.A.; de Jong, M.D.E.; Steegh, A.; Ouborg, N.J.; Van Groenendael, J.M.; Klaassen, M.R.J.

    2006-01-01

    1. The potential for seed dispersal by fish (ichthyochory) will vary among aquatic plants because of differences in seed size and morphology. 2. To examine how seed morphology influences the probability of dispersal by the common carp (Cyprinus carpio), we studied seed ingestion, retention time and

  13. The role of animal seed dispersal in accelerating native forest regeneration on degraded tropical lands.

    Science.gov (United States)

    J.M. Wunderle Jr.

    1997-01-01

    this paper reviews the characteristicas of animal seed dispersal. relevant to tropical forest restoration efforts and discusses their managment implication. In many tropical regions seed dispersal by animals is the predominant form of dissemination of propagules and has a potential to facilitate recolonization of native vegetation on degraded sites.

  14. Refaunation and the reinstatement of the seed-dispersal function in Gorongosa National Park

    OpenAIRE

    Correia, Marta; Timóteo, Sérgio; Rodríguez-Echeverría, Susana; Mazars-Simon, Alban; Heleno, Ruben

    2017-01-01

    Large animals are important seed dispersers; however, they tend to be under a high extinction risk worldwide. There is compelling evidence that the global biodiversity crisis is leading to the deterioration of several ecosystem functions, but there is virtually no information on how large-scale refaunation efforts can reinstate seed dispersal. We evaluated the effectiveness of a 62-km(2) wildlife sanctuary, which was established to recover populations of large mammals in Gorongosa National Pa...

  15. A new hypothesis for the importance of seed dispersal in time

    Directory of Open Access Journals (Sweden)

    Adriana Guzmán

    2011-12-01

    Full Text Available Most studies on seed dispersal in time have focused on seed dormancy and the physiological triggers for germination. However, seed dispersed by animals with low metabolic and moving rates, and long gutpassage times such as terrestrial turtles, could be considered another type of dispersal in time. This study tests the hypothesis that seeds dispersed in time may lower predation rates. We predicted that seeds deposited below parent trees after fruiting fall has finished is advantageous to minimize seed predators and should show higher survival rates. Four Amazonian plant species, Dicranostyles ampla, Oenocarpus bataua, Guatteria atabapensis and Ocotea floribunda, were tested for seed survival probabilities in two periods: during fruiting and 10-21 days after fruiting. Experiments were carried out in two biological stations located in the Colombian Amazon (Caparú and Zafire Biological Stations. Seed predation was high and mainly caused by non-vertebrates. Out of the four plant species tested, only Guatteria atabapensis supported the time escape hypothesis. For this species, seed predation by vertebrates after the fruiting period increased (from 4.1% to 9.2% while seed predation by nonvertebrates decreased (from 54.0% to 40.2%. In contrast, seed predation by vertebrates and by non-vertebrates after the fruiting period in D. ampla increased (from 7.9% to 22.8% and from 40.4% to 50.6%, respectively, suggesting predator satiation. Results suggest that for some species dispersal in time could be advantageous to avoid some type of seed predators. Escape in time could be an additional dimension in which seeds may reach adequate sites for recruitment. Thus, future studies should be address to better understand the survival advantages given by an endozoochory time-dispersal process. Rev. Biol. Trop. 59 (4: 1795-1803. Epub 2011 December 01.La mayoría de estudios sobre dispersión de semillas en el tiempo tratan sobre la dormancia de las semillas y los

  16. Evaluating realized seed dispersal across fragmented tropical landscapes: a two-fold approach using parentage analysis and the neighbourhood model.

    Science.gov (United States)

    Ismail, Sascha A; Ghazoul, Jaboury; Ravikanth, Gudasalamani; Kushalappa, Cheppudira G; Uma Shaanker, Ramanan; Kettle, Chris J

    2017-05-01

    Despite the importance of seed dispersal for survival of plant species in fragmented landscapes, data on seed dispersal at landscape scales remain sparse. Effective seed dispersal among fragments determines recolonization and plant species persistence in such landscapes. We present the first large-scale (216-km 2 ) direct estimates of realized seed dispersal of a high-value timber tree (Dysoxylum malabaricum) across an agro-forest landscape in the Western Ghats, India. Based upon an exhaustive inventory of adult trees and a sample of 488 seedlings all genotyped at 10 microsatellite loci, we estimated realized seed dispersal using parentage analysis and the neighbourhood model. Our estimates found that most realized seed dispersal was within 200 m, which is insufficient to effectively bridge the distances between forest patches. We conclude that using mobility of putative animal dispersers can be misleading when estimating tropical tree species vulnerability to habitat fragmentation. This raises serious concerns about the potential of many tropical trees to recolonize isolated forest patches where high-value tree species have already been removed. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  17. The experimental study of seed dispersal by fish (ichthyochory)

    NARCIS (Netherlands)

    Pollux, B.J.A.

    2011-01-01

    1.The last few years have seen an increased interest in the experimental study of seed dispersal by fish (ichthyochory). This paper reviews such experiments, aiming to determine what functional aspects of ichthyochory have been investigated, what experimental designs have been used and what the

  18. High seed dispersal ability of Pinus canariensis in stands of contrasting density inferred from genotypic data

    Directory of Open Access Journals (Sweden)

    Unai López de Heredia

    2015-04-01

    Full Text Available Aim of the study: Models that combine parentage analysis from molecular data with spatial information of seeds and seedlings provide a framework to describe and identify the factors involved in seed dispersal and recruitment of forest species. In the present study we used a spatially explicit method (the gene shadow model in order to assess primary and effective dispersal in Pinus canariensis. Area of study: Pinus canariensis is endemic to the Canary Islands (Spain. Sampling sites were a high density forest in southern slopes of Tenerife and a low density stand in South Gran Canaria. Materials and methods: We fitted models based on parentage analysis from seeds and seedlings collected in two sites with contrasting stand density, and then compared the resulting dispersal distributions. Main results: The results showed that: 1 P. canariensis has a remarkable dispersal ability compared to other pine species; 2 there is no discordance between primary and effective dispersals, suggesting limited secondary dispersal by animals and lack of Janzen-Connell effect; and 3 low stand densities enhance the extent of seed dispersal, which was higher in the low density stand. Research highlights: The efficient dispersal mechanism of P. canariensis by wind inferred by the gene shadow model is congruent with indirect measures of gene flow, and has utility in reconstructing past demographic events and in predicting future distribution ranges for the species.

  19. The effect of feeding time on dispersal of Virola seeds by toucans determined from GPS tracking and accelerometers

    NARCIS (Netherlands)

    Kays, Roland; Jansen, Patrick A.; Knecht, Elise M. H.; Vohwinkel, Reinhard; Wikelski, Martin

    2011-01-01

    Seed dispersal is critical to understanding forest dynamics but is hard to study because tracking seeds is difficult. Even for the best-studied dispersal system of the Neotropics, Virola nobilis, the dispersal kernel remains unknown. We combined high-resolution GPS/3D-acceleration bird tracking,

  20. Divergent chemical cues elicit seed collecting by ants in an obligate multi-species mutualism in lowland Amazonia.

    Directory of Open Access Journals (Sweden)

    Elsa Youngsteadt

    2010-12-01

    Full Text Available In lowland Amazonian rainforests, specific ants collect seeds of several plant species and cultivate them in arboreal carton nests, forming species-specific symbioses called ant-gardens (AGs. In this obligate mutualism, ants depend on the plants for nest stability and the plants depend on ant nests for substrate and nutrients. AG ants and plants are abundant, dominant members of lowland Amazonian ecosystems, but the cues ants use to recognize the seeds are poorly understood. To address the chemical basis of the ant-seed interaction, we surveyed seed chemistry in nine AG species and eight non-AG congeners. We detected seven phenolic and terpenoid volatiles common to seeds of all or most of the AG species, but a blend of the shared compounds was not attractive to the AG ant Camponotus femoratus. We also analyzed seeds of three AG species (Anthurium gracile, Codonanthe uleana, and Peperomia macrostachya using behavior-guided fractionation. At least one chromatographic fraction of each seed extract elicited retrieval behavior in C. femoratus, but the active fractions of the three plant species differed in polarity and chemical composition, indicating that shared compounds alone did not explain seed-carrying behavior. We suggest that the various AG seed species must elicit seed-carrying with different chemical cues.

  1. Pollination and seed dispersal of Aquilaria sinensis (Lour. Gilg (Thymelaeaceae: An economic plant species with extremely small populations in China

    Directory of Open Access Journals (Sweden)

    Gao Chen

    2016-10-01

    Full Text Available Pollination and seed dispersal in angiosperms have long been investigated in order to understand the coevolution of plants and animals. However, the signals from flowers and/or seeds to attract pollinators and/or seed dispersers have received comparatively little attention. In this study, the pollination biology and seed dispersal of the vulnerable agarwood plant Aquilaria sinensis (Lour. Gilg, a traditional medicinal plant in China, was studied in its natural distribution range. The reproductive tactics of A. sinensis were studied in detail by employing various tests dealing with fruit set and also seed dispersal. Dynamic headspace extraction followed by GC-MS analysis was also performed in order to reveal the composition of floral scent. The results showed that noctuids and pyralids are the most effective pollinators of pollinator-dependent A. sinensis. The main compounds of the floral scent were (E, E-α-Farnesene (61.9 ± 3.2%, trans-Ocimene (16.6 ± 1.2%, and Benzyl salicylate (4.6 ± 1.1%. The results obtained from seed dispersal experiments indicate that hornets are effective seed dispersers and they may play an important role in long-distance seed dispersal of A. sinensis. Based on our findings, we recommend several protection methods for this threatened agarwood plant in China.

  2. Seed dispersal by vertebrates in Madagascar's forests: review and ...

    African Journals Online (AJOL)

    Seed dispersal by vertebrates in Madagascar's forests: review and future directions. ... provides a helpful Frequently Asked Questions about PDFs. Alternatively, you can download the PDF file directly to your computer, from where it can be opened using a PDF reader. To download the PDF, click the Download link above.

  3. Testing hypotheses for excess flower production and low fruit-to-flower ratios in a pollinating seed-consuming mutualism

    Science.gov (United States)

    Holland, J. Nathaniel; Bronstein, Judith L.; DeAngelis, Donald L.

    2004-01-01

    Pollinator attraction, pollen limitation, resource limitation, pollen donation and selective fruit abortion have all been proposed as processes explaining why hermaphroditic plants commonly produce many more flowers than mature fruit. We conducted a series of experiments in Arizona to investigate low fruit-to-flower ratios in senita cacti, which rely exclusively on pollinating seed-consumers. Selective abortion of fruit based on seed predators is of particular interest in this case because plants relying on pollinating seed-consumers are predicted to have such a mechanism to minimize seed loss. Pollinator attraction and pollen dispersal increased with flower number, but fruit set did not, refuting the hypothesis that excess flowers increase fruit set by attracting more pollinators. Fruit set of natural- and hand-pollinated flowers were not different, supporting the resource, rather than pollen, limitation hypothesis. Senita did abort fruit, but not selectively based on pollen quantity, pollen donors, or seed predators. Collectively, these results are consistent with sex allocation theory in that resource allocation to excess flower production can increase pollen dispersal and the male fitness function of flowers, but consequently results in reduced resources available for fruit set. Inconsistent with sex allocation theory, however, fruit production and the female fitness function of flowers may actually increase with flower production. This is because excess flower production lowers pollinator-to-flower ratios and results in fruit abortion, both of which limit the abundance and hence oviposition rates, of pre-dispersal seed predators.

  4. Seed dispersal by small herbivores and tidal water : are they important filters in the assembly of salt-marsh communities?

    NARCIS (Netherlands)

    Chang, ER; Zozaya, EL; Kuijper, DPJ; Bakker, JP

    1. Characteristics of internal seed dispersal (endozoochory) by European Brown Hares were compared with similar dispersal by Brent Geese. Hares deposited more seeds of mid-successional, perennial, high-marsh species than did geese, which deposited more seeds of early successional, annual, low-marsh

  5. Seed dispersal by small herbivores and tidal water: Are they important filters in the assembly of salt-marsh communities?

    NARCIS (Netherlands)

    Chang, E.R.; Zozaya, E.L.; Kuijper, D.P.J.; Bakker, J.P.

    2005-01-01

    1. Characteristics of internal seed dispersal (endozoochory) by European Brown Hares were compared with similar dispersal by Brent Geese. Hares deposited more seeds of mid-successional, perennial, high-marsh species than did geese, which deposited more seeds of early successional, annual, low-marsh

  6. Seed dispersal of a useful palm (Astrocaryum chambira Burret) in three amazonian forests with different human intervention used in ecological restoration

    International Nuclear Information System (INIS)

    Ramirez Beatriz H; Parrado Rosselli Angela; Stevenson Pablo

    2009-01-01

    The young leaves of Astrocaryum chambira are used by the indigenous people in the Amazon as raw material for handicrafts. However, few studies have been made on the natural history of this palm and on the indirect impact caused by the decrease of its dispersal agents. Considering that the loss of animal dispersal vectors due to hunting and landscape modification can affect seed dispersal processes of tropical forest plants, the goal of this study was to compare seed dispersal of A. chambira in three terra firme forests of the Colombian Amazon, with different degrees of human intervention. We censused densities of dispersal agents of A. chambira, and characterized the seed shadow. We also marked seeds to estimate dispersal distances, and established density and distance-dependent experimental stations to assess their relevance on seed dispersal. The results showed that seed removal was proportional to dispersal agent densities and forest intervention levels. Insects were the main seed predators in all sites but their effect was less pronounced in the low intervened forest site. Seed density did not show any effect on removal, while a higher probability of survival at intermediate distances from the parent palm (10 m) was found. Future studies should focus on seedling establishment, recruitment rates and the effects of human intervention on subsequent life stages of the palm.

  7. Are weeds hitchhiking a ride on your car? A systematic review of seed dispersal on cars.

    Directory of Open Access Journals (Sweden)

    Michael Ansong

    Full Text Available When traveling in cars, we can unintentionally carry and disperse weed seed; but which species, and where are they a problem? To answer these questions, we systematically searched the scientific literature to identify all original research studies that assess seed transported by cars and listed the species with seed on/in cars. From the 13 studies that fit these criteria, we found 626 species from 75 families that have seed that can be dispersed by cars. Of these, 599 are listed as weeds in some part of the world, with 439 listed as invasive or naturalized alien species in one or more European countries, 248 are invasive/noxious weeds in North America, 370 are naturalized alien species in Australia, 167 are alien species in India, 77 are invasive species in China and 23 are declared weeds/invaders in South Africa. One hundred and one are classified as internationally important environmental weeds. Although most (487 were only recorded once, some species such as Chenopodium album, Poa pratensis and Trifolium repens were common among studies. Perennial graminoids seem to be favoured over annual graminoids while annual forbs are favoured over perennial forbs. Species characteristics including seed size and morphology and where the plants grew affected the probability that their seed was transported by cars. Seeds can be found in many different places on cars including under the chassis, front and rear bumpers, wheel wells and rims, front and back mudguards, wheel arches, tyres and on interior floor mats. With increasing numbers of cars and expanding road networks in many regions, these results highlight the importance of cars as a dispersal mechanism, and how it may favour invasions by some species over others. Strategies to reduce the risk of seed dispersal by cars include reducing seed on cars by mowing road verges and cleaning cars.

  8. Does animal-mediated seed dispersal facilitate the formation of Pinus armandii-Quercus aliena var. acuteserrata forests?

    Science.gov (United States)

    Yu, Fei; Wang, Dexiang; Yi, Xianfeng; Shi, Xiaoxiao; Huang, Yakun; Zhang, Hongwu; Zhang, XinPing

    2014-01-01

    The Pinus armandii and Quercus aliena var. acuteserrata mixed forest is one of the major forest types in the Qinling Mountains, China. P. armandii is considered to be a pioneer species during succession and it is usually invaded by late successional Q. aliena var. acuteserrata. However, the mechanism that underlies its invasion remains unclear. In the present study, we tracked seed dispersal of P. armandii and Q. aliena var. acuteserrata using coded plastic tags in the western, middle and eastern Qinling Mountains to elucidate the invasion process in the mixed forests. Our results indicated that the seeds of both P. armandii and Q. aliena var. acuteserrata were removed rapidly in the Qinling Mountains, and there were no differences in the seed removal rates between the two species. There were significant differences in rodent seed-eating and caching strategies between the two tree species. For P. armandii, seeds were more likely to be eaten in situ than those of Q. aliena var. acuteserrata in all plots. By contrast, the acorns of Q. aliena var. acuteserrata were less frequently eaten in situ, but more likely to be removed and cached. Q. aliena var. acuteserrata acorns had significantly longer dispersal distances than P. armandii seeds in all plots. Although P. armandii seeds were less likely to be dispersed into the Q. aliena var. acuteserrata stands, over 30% of the released acorns were transported into the P. armandii stands where they established five seedlings. Based on the coupled recruitment patterns of P. armandii and Q. aliena var. acuteserrata, we suggest that the animal-mediated seed dispersal contributes to the formation of Pinus armandii-Quercus aliena var. acuteserrata forests.

  9. Black howler monkey (Alouatta pigra) activity, foraging and seed dispersal patterns in shaded cocoa plantations versus rainforest in southern Mexico.

    Science.gov (United States)

    Zárate, Diego A; Andresen, Ellen; Estrada, Alejandro; Serio-Silva, Juan Carlos

    2014-09-01

    Recent evidence has shown that primates worldwide use agroecosystems as temporary or permanent habitats. Detailed information on how these primates are using these systems is scant, and yet their role as seed dispersers is often implied. The main objective of this study was to compare the activity, foraging patterns and seed dispersal role of black howler monkeys (Alouatta pigra) inhabiting shaded cocoa plantations and rainforest in southern Chiapas, Mexico. We gathered data on three monkey groups living in shaded cocoa plantations and three groups living in rainforest, using focal sampling, and collecting fecal samples. General activity and foraging patterns were similar in both habitats, with the exception that monkeys in the cocoa habitat spent more time feeding on petioles. Monkeys in shaded cocoa plantations dispersed 51,369 seeds (4% were seeds ≥3 mm width) of 16 plant species. Monkeys in the rainforest dispersed 6,536 seeds (78% were seeds ≥3 mm width) of 13 plant species. Our data suggest that the difference between habitats in the proportion of large versus small seeds dispersed reflects differences in fruit species abundance and availability in cocoa versus forest. Mean seed dispersal distances were statistically similar in both habitats (cocoa = 149 m, forest = 86 m). We conclude that the studied cocoa plantations provide all elements necessary to constitute a long-term permanent habitat for black howler monkeys. In turn, howler monkeys living in these plantations are able to maintain their functional role as seed dispersers for those native tree and liana species present within their areas of activities. © 2014 Wiley Periodicals, Inc.

  10. Ecological consequences of primary and secondary seed dispersal on seed and seedling fate of Dipteryx oleifera (Fabaceae

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    Javier Ruiz

    2010-09-01

    Full Text Available The relative contributions of primary and secondary seed dispersal to plant demography have received little investigation. Evidence on these seed dispersal types, on seed fate and seedling recruitment of the tropical rain forest tree Dipteryx oleifera, is presented. The study was conducted in a 6.37ha permanent plot where seeds and seedlings were located and tagged for the 2007 cohort. A total of 2 814 seeds were threaded and their fate was followed one year after germination. Primary seed dispersal by bats protected seeds from insect larval predation below the adult tree. Bats congregated seeds in bat seed piles located at a mean distance of 40.94±1.48m from the nearest adult individual of D. oleifera. Terrestrial vertebrates congregated seeds in caches located 41.90±2.43m from the nearest adult individual of D. oleifera. The results of the fitted proportional hazard model suggested that primary seed dispersal decreased seed hazard probability by 1.12% for each meter from the adult conspecific (pPresentamos evidencia de la contribución relativa de la dispersión primaria y secundaria de semillas en la suerte que corren las mismas y en el reclutamiento de plántulas de la especie de bosque húmedo tropical Dipteryx oleifera. Este estudio fue realizado en una parcela permanente de 6.37 ha en la que semillas y plántulas del cohorte del 2007 fueron localizadas y mapeadas. Etiquetamos 2 814 semillas para evaluar su suerte un año después de la germinación. Encontramos que la dispersión primaria por murciélagos libera a las semillas de la depredación bajo la copa del árbol adulto causada por la fase larval de un insecto. Los murciélagos dispersan semillas bajo la copa de palmas usadas como comederos, localizados a 40.94±1.48m del árbol de D. oleifera más cercano y vertebrados terrestres congregaran las semillas en caches localizados aproximadamente a 41.90±2.43m del árbol de D. oleifera. Un modelo proporcional de riesgos fue ajustado

  11. Edge effect on post-dispersal artificial seed predation in the southeastern Amazonia, Brazil.

    Science.gov (United States)

    Penido, G; Ribeiro, V; Fortunato, D S

    2015-05-01

    This paper evaluates the post-dispersal artificial seed predation rates in two areas of the southeastern Amazon forest-savanna boundary, central Brazil. We conducted the survey in a disturbance regime controlled research site to verify if exists an edge effect in these rates and if the disturbance (in this case annual fire and no fire) affects seed predation. We placed 800 peanuts seeds in each area at regular distance intervals from the fragment`s edge. Data were analyzed by a likelihood ratio model selection in generalized linear models (GLM). The complete model (with effects from edge distance and site and its interaction) was significative (F3=4.43; p=0.005). Seeds had a larger predation rates in fragment's interior in both areas, but in the controlled area (no disturbance) this effect was less linear. This suggests an edge effect for post-dispersal seed predation, and that disturbances might alter these effects. Even if we exclude the site effect (grouping both areas together) there is still a strong edge effect on seed predation rates (F3=32.679; p>0.001). We did not verify predator's species in this study; however, the presence of several species of ants was extremely common in the seeds. The detection of an edge effect in only a short survey time suggests that there is heterogeneity in predation rates and that this variation might affect plant recruitment in fragmented areas of the Amazon forest. Henceforth, this seed predation should be taken in consideration in reforestation projects, where the main source of plants species is from seed distribution.

  12. Gopherus agassizii (Desert Tortoise). Non-native seed dispersal

    Science.gov (United States)

    Ennen, J.R.; Loughran, Caleb L.; Lovich, Jeffrey E.

    2011-01-01

    Sahara Mustard (Brassica tournefortii) is a non-native, highly invasive weed species of southwestern U.S. deserts. Sahara Mustard is a hardy species, which flourishes under many conditions including drought and in both disturbed and undisturbed habitats (West and Nabhan 2002. In B. Tellman [ed.], Invasive Plants: Their Occurrence and Possible Impact on the Central Gulf Coast of Sonora and the Midriff Islands in the Sea of Cortes, pp. 91–111. University of Arizona Press, Tucson). Because of this species’ ability to thrive in these habitats, B. tournefortii has been able to propagate throughout the southwestern United States establishing itself in the Mojave and Sonoran Deserts in Arizona, California, Nevada, and Utah. Unfortunately, naturally disturbed areas created by native species, such as the Desert Tortoise (Gopherus agassizii), within these deserts could have facilitated the propagation of B. tournefortii. (Lovich 1998. In R. G. Westbrooks [ed.], Invasive Plants, Changing the Landscape of America: Fact Book, p. 77. Federal Interagency Committee for the Management of Noxious and Exotic Weeds [FICMNEW], Washington, DC). However, Desert Tortoises have never been directly observed dispersing Sahara Mustard seeds. Here we present observations of two Desert Tortoises dispersing Sahara Mustard seeds at the interface between the Mojave and Sonoran deserts in California.

  13. Seed dispersal and movement patterns in two species of Ceratogymna hornbills in a West African tropical lowland forest.

    Science.gov (United States)

    Holbrook, Kimberly M; Smith, Thomas B

    2000-10-01

    We studied two species of Ceratogymna hornbills, the black-casqued hornbill, C. atrata, and the white-thighed hornbill, C. cylindricus, in the tropical forests of Cameroon, to understand their movement patterns and evaluate their effectiveness as seed dispersers. To estimate hornbill contribution to a particular tree species' seed shadow we combined data from movements, determined by radio-tracking, with data from seed passage trials. For 13 individuals tracked over 12 months, home range varied between 925 and 4,472 ha, a much larger area than reported for other African avian frugivores. Seed passage times ranged from 51 to 765 min, with C. atrata showing longer passage times than C. cylindricus, and larger seeds having longer gut retention times than smaller seeds. Combining these data, we estimated that seed shadows were extensive for the eight tree species examined, with approximately 80% of seeds moved more than 500 m from the parent plant. Maximum estimated dispersal distances for larger seeds were 6,919 and 3,558 m for C. atrata and C. cylindricus, respectively. The extent of hornbill seed shadows suggests that their influence in determining forest structure will likely increase as other larger mammalian dispersers are exterminated.

  14. Disentangling the role of seed bank and dispersal in plant metapopulation dynamics using patch occupancy surveys.

    Science.gov (United States)

    Manna, F; Pradel, R; Choquet, R; Fréville, H; Cheptou, P-O

    2017-10-01

    In plants, the presence of a seed bank challenges the application of classical metapopulation models to aboveground presence surveys; ignoring seed bank leads to overestimated extinction and colonization rates. In this article, we explore the possibility to detect seed bank using hidden Markov models in the analysis of aboveground patch occupancy surveys of an annual plant with limited dispersal. Patch occupancy data were generated by simulation under two metapopulation sizes (N = 200 and N = 1,000 patches) and different metapopulation scenarios, each scenario being a combination of the presence/absence of a 1-yr seed bank and the presence/absence of limited dispersal in a circular 1-dimension configuration of patches. In addition, because local conditions often vary among patches in natural metapopulations, we simulated patch occupancy data with heterogeneous germination rate and patch disturbance. Seed bank is not observable from aboveground patch occupancy surveys, hence hidden Markov models were designed to account for uncertainty in patch occupancy. We explored their ability to retrieve the correct scenario. For 10 yr surveys and metapopulation sizes of N = 200 or 1,000 patches, the correct metapopulation scenario was detected at a rate close to 100%, whatever the underlying scenario considered. For smaller, more realistic, survey duration, the length for a reliable detection of the correct scenario depends on the metapopulation size: 3 yr for N = 1,000 and 6 yr for N = 200 are enough. Our method remained powerful to disentangle seed bank from dispersal in the presence of patch heterogeneity affecting either seed germination or patch extinction. Our work shows that seed bank and limited dispersal generate different signatures on aboveground patch occupancy surveys. Therefore, our method provides a powerful tool to infer metapopulation dynamics in a wide range of species with an undetectable life form. © 2017 by the Ecological Society of America.

  15. Passive restoration following ungulate removal in a highly disturbed tropical wet forest devoid of native seed dispersers

    Science.gov (United States)

    Nafus, Melia; Savidge, Julie A.; Yackel Adams, Amy A.; Christy, Michelle T.; Reed, Robert

    2018-01-01

    Overabundant ungulate populations can alter forests. Concurrently, global declines of seed dispersers may threaten native forest structure and function. On an island largely devoid of native vertebrate seed dispersers, we monitored forest succession for 7 years following ungulate exclusion from a 5-ha area and adjacent plots with ungulates still present. We observed succession from open scrub to forest and understory cover by non-native plants declined. Two trees, native Hibiscus tiliaceus and non-native Leucaena leucocephala, accounted for most forest regeneration, with the latter dominant. Neither species is dependent on animal dispersers nor was there strong evidence that plants dependent on dispersers migrated into the 5-ha study area. Passive restoration following ungulate removal may facilitate restoration, but did not show promise for fully restoring native forest on Guam. Restoration of native forest plants in bird depopulated areas will likely require active outplanting of native seedlings, control of factors resulting in bird loss, and reintroduction of seed dispersers.

  16. Edge effect on post-dispersal artificial seed predation in the southeastern Amazonia, Brazil

    Directory of Open Access Journals (Sweden)

    G. Penido

    Full Text Available This paper evaluates the post-dispersal artificial seed predation rates in two areas of the southeastern Amazon forest-savanna boundary, central Brazil. We conducted the survey in a disturbance regime controlled research site to verify if exists an edge effect in these rates and if the disturbance (in this case annual fire and no fire affects seed predation. We placed 800 peanuts seeds in each area at regular distance intervals from the fragment`s edge. Data were analyzed by a likelihood ratio model selection in generalized linear models (GLM. The complete model (with effects from edge distance and site and its interaction was significative (F3=4.43; p=0.005. Seeds had a larger predation rates in fragment’s interior in both areas, but in the controlled area (no disturbance this effect was less linear. This suggests an edge effect for post-dispersal seed predation, and that disturbances might alter these effects. Even if we exclude the site effect (grouping both areas together there is still a strong edge effect on seed predation rates (F3=32.679; p>0.001. We did not verify predator’s species in this study; however, the presence of several species of ants was extremely common in the seeds. The detection of an edge effect in only a short survey time suggests that there is heterogeneity in predation rates and that this variation might affect plant recruitment in fragmented areas of the Amazon forest. Henceforth, this seed predation should be taken in consideration in reforestation projects, where the main source of plants species is from seed distribution.

  17. Benefit and cost curves for typical pollination mutualisms.

    Science.gov (United States)

    Morris, William F; Vázquez, Diego P; Chacoff, Natacha P

    2010-05-01

    Mutualisms provide benefits to interacting species, but they also involve costs. If costs come to exceed benefits as population density or the frequency of encounters between species increases, the interaction will no longer be mutualistic. Thus curves that represent benefits and costs as functions of interaction frequency are important tools for predicting when a mutualism will tip over into antagonism. Currently, most of what we know about benefit and cost curves in pollination mutualisms comes from highly specialized pollinating seed-consumer mutualisms, such as the yucca moth-yucca interaction. There, benefits to female reproduction saturate as the number of visits to a flower increases (because the amount of pollen needed to fertilize all the flower's ovules is finite), but costs continue to increase (because pollinator offspring consume developing seeds), leading to a peak in seed production at an intermediate number of visits. But for most plant-pollinator mutualisms, costs to the plant are more subtle than consumption of seeds, and how such costs scale with interaction frequency remains largely unknown. Here, we present reasonable benefit and cost curves that are appropriate for typical pollinator-plant interactions, and we show how they can result in a wide diversity of relationships between net benefit (benefit minus cost) and interaction frequency. We then use maximum-likelihood methods to fit net-benefit curves to measures of female reproductive success for three typical pollination mutualisms from two continents, and for each system we chose the most parsimonious model using information-criterion statistics. We discuss the implications of the shape of the net-benefit curve for the ecology and evolution of plant-pollinator mutualisms, as well as the challenges that lie ahead for disentangling the underlying benefit and cost curves for typical pollination mutualisms.

  18. Myiarchus flycatchers are the primary seed dispersers of Bursera longipes in a Mexican dry forest

    Directory of Open Access Journals (Sweden)

    R. Carlos Almazán-Núñez

    2016-06-01

    Full Text Available We evaluated the seed dispersal of Bursera longipes by birds along a successional gradient of tropical dry forest (TDF in southwestern Mexico. B. longipes is an endemic tree to the TDF in the Balsas basin. The relative abundance of frugivorous birds, their frequency of visits to B. longipes and the number of removed fruits were recorded at three study sites with different stages of forest succession (early, intermediate and mature characterized by distinct floristic and structural elements. Flycatchers of the Myiarchus and Tyrannus genera removed the majority of fruits at each site. Overall, visits to B. longipes were less frequent at the early successional site. Birds that function as legitimate dispersers by consuming whole seeds and regurgitating or defecating intact seeds in the process also remove the pseudoaril from seeds, thereby facilitating the germination process. The highest germination percentages were recorded for seeds that passed through the digestive system of two migratory flycatchers: M. cinerascens and M. nutingii. Perch plants, mainly composed of legumes (e.g., Eysenhardtia polystachya, Acacia cochliacantha, Calliandra eryophylla, Mimosa polyantha, serve also as nurse plants since the number of young individuals recruited from B. longipes was higher under these than expected by chance. This study shows that Myiarchus flycatchers are the most efficient seed dispersers of B. longipes across all successional stages. This suggests a close mutualistic relationship derived from adaptive processes and local specializations throughout the distribution of both taxa, as supported by the geographic mosaic theory of coevolution.

  19. Multilayer networks reveal the spatial structure of seed-dispersal interactions across the Great Rift landscapes.

    Science.gov (United States)

    Timóteo, Sérgio; Correia, Marta; Rodríguez-Echeverría, Susana; Freitas, Helena; Heleno, Ruben

    2018-01-10

    Species interaction networks are traditionally explored as discrete entities with well-defined spatial borders, an oversimplification likely impairing their applicability. Using a multilayer network approach, explicitly accounting for inter-habitat connectivity, we investigate the spatial structure of seed-dispersal networks across the Gorongosa National Park, Mozambique. We show that the overall seed-dispersal network is composed by spatially explicit communities of dispersers spanning across habitats, functionally linking the landscape mosaic. Inter-habitat connectivity determines spatial structure, which cannot be accurately described with standard monolayer approaches either splitting or merging habitats. Multilayer modularity cannot be predicted by null models randomizing either interactions within each habitat or those linking habitats; however, as habitat connectivity increases, random processes become more important for overall structure. The importance of dispersers for the overall network structure is captured by multilayer versatility but not by standard metrics. Highly versatile species disperse many plant species across multiple habitats, being critical to landscape functional cohesion.

  20. Avian frugivory and seed dispersal of Indian Sandalwood Santalum album in Tamil Nadu, India

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    P. Balasubramanian

    2011-05-01

    Full Text Available Santalum album, a medium sized evergreen tree found in dry forest tracts of the Deccan Peninsula, India is vulnerable (IUCN and red listed species in southern India. The paper discusses the role of avian frugivores in seed dissemination of S.album in Tamil Nadu. Observations from different locations of Western and Eastern Ghats of Tamil Nadu are presented. The forest type of the study sites comprise of southern dry mixed deciduous forest. Extended watches of 3-hr duration were made on focal trees. During the extended observations, the observer noted the name of the visitor, frequency of fruit-feeding visits by different species, and fruit handling behaviour. A total of 10 species of birds and Three-striped Palm Squirrel foraged fruit crops. Birds constituted the principal seed dispersers of Santalum album. Role of Indian Grey Hornbill in regeneration of S. album was evidenced by the presence of sandalwood seedlings in hornbill’s nest middens. Although bulbuls made frequent foraging visits, they ate the fruits in piecemeal and did not move the seeds away from the parent trees. Among the avian foragers, Asian Koel, Common Myna, Brahminy Starling, Brown-headed Barbet, White-headed Babbler and Indian Grey Hornbill constituted the major seed dispersers of S.album. These birds visited the fruit crops more frequently and swallowed the fruits wholly. Conservation efforts need to focus in providing a healthy habitat for the seed dispersing birds such as koel, as the population of sandalwood tree is dwindling in the wild.

  1. Legitimate seed dispersal by lizards in an alpine habitat: The case of Berberis empetrifolia (Berberidaceae) dispersed by Liolaemus belii (Tropiduridae)

    Science.gov (United States)

    Celedón-Neghme, Constanza; San Martin, Leonardo A.; Victoriano, Pedro F.; Cavieres, Lohengrin A.

    2008-05-01

    In this study we determined the effect of seed passage through Liolaemus bellii lizard digestive tracts on germination of fleshy-fruited Andean shrub species Berberis empetrifolia (Berberidaceae), and evaluated the effect of this passage on seed coat characteristics. In addition, we assessed the spatial patterns of fecal deposition by lizards onto various microhabitats available in the Andean environments of central Chile. The germination rate and the final percentage of lizard-ingested B. empetrifolia seeds was greater than control seeds. Comparing photographs and seed coat histological cuts, we suggest that the cutine wax present on seed coats from lizard-ingested seeds was probably removed by abrasion inside the lizards' digestive tract. Sixty-two percent of the lizard's feces was deposited on bare soil near rocks commonly inhabited by lizards. However, this microhabitat represents only 29% of the available ground cover at the study site. By enhancing seed germination and depositing seeds onto potential safe sites for recruitment, the lizard Liolaemus bellii is acting, at least qualitatively, as an effective disperser of Berberis empetrifolia.

  2. Directed seed dispersal towards areas with low conspecific tree density by a scatter-hoarding rodent

    NARCIS (Netherlands)

    Hirsch, Ben T.; Kays, Roland; Pereira, Veronica E.; Jansen, Patrick A.

    2012-01-01

    Scatter-hoarding animals spread out cached seeds to reduce density-dependent theft of their food reserves. This behaviour could lead to directed dispersal into areas with lower densities of conspecific trees, where seed and seedling survival are higher, and could profoundly affect the spatial

  3. Noise pollution alters ecological services: enhanced pollination and disrupted seed dispersal.

    Science.gov (United States)

    Francis, Clinton D; Kleist, Nathan J; Ortega, Catherine P; Cruz, Alexander

    2012-07-22

    Noise pollution is a novel, widespread environmental force that has recently been shown to alter the behaviour and distribution of birds and other vertebrates, yet whether noise has cumulative, community-level consequences by changing critical ecological services is unknown. Herein, we examined the effects of noise pollution on pollination and seed dispersal and seedling establishment within a study system that isolated the effects of noise from confounding stimuli common to human-altered landscapes. Using observations, vegetation surveys and pollen transfer and seed removal experiments, we found that effects of noise pollution can reverberate through communities by disrupting or enhancing these ecological services. Specifically, noise pollution indirectly increased artificial flower pollination by hummingbirds, but altered the community of animals that prey upon and disperse Pinus edulis seeds, potentially explaining reduced P. edulis seedling recruitment in noisy areas. Despite evidence that some ecological services, such as pollination, may benefit indirectly owing to noise, declines in seedling recruitment for key-dominant species such as P. edulis may have dramatic long-term effects on ecosystem structure and diversity. Because the extent of noise pollution is growing, this study emphasizes that investigators should evaluate the ecological consequences of noise alongside other human-induced environmental changes that are reshaping human-altered landscapes worldwide.

  4. Noise pollution alters ecological services: enhanced pollination and disrupted seed dispersal

    Science.gov (United States)

    Francis, Clinton D.; Kleist, Nathan J.; Ortega, Catherine P.; Cruz, Alexander

    2012-01-01

    Noise pollution is a novel, widespread environmental force that has recently been shown to alter the behaviour and distribution of birds and other vertebrates, yet whether noise has cumulative, community-level consequences by changing critical ecological services is unknown. Herein, we examined the effects of noise pollution on pollination and seed dispersal and seedling establishment within a study system that isolated the effects of noise from confounding stimuli common to human-altered landscapes. Using observations, vegetation surveys and pollen transfer and seed removal experiments, we found that effects of noise pollution can reverberate through communities by disrupting or enhancing these ecological services. Specifically, noise pollution indirectly increased artificial flower pollination by hummingbirds, but altered the community of animals that prey upon and disperse Pinus edulis seeds, potentially explaining reduced P. edulis seedling recruitment in noisy areas. Despite evidence that some ecological services, such as pollination, may benefit indirectly owing to noise, declines in seedling recruitment for key-dominant species such as P. edulis may have dramatic long-term effects on ecosystem structure and diversity. Because the extent of noise pollution is growing, this study emphasizes that investigators should evaluate the ecological consequences of noise alongside other human-induced environmental changes that are reshaping human-altered landscapes worldwide. PMID:22438504

  5. Stability and generalization in seed dispersal networks: a case study of frugivorous fish in Neotropical wetlands.

    Science.gov (United States)

    Correa, Sandra Bibiana; Arujo, Joisiane K; Penha, Jerry; Nunes da Cunha, Catia; Bobier, Karen E; Anderson, Jill T

    2016-08-31

    When species within guilds perform similar ecological roles, functional redundancy can buffer ecosystems against species loss. Using data on the frequency of interactions between fish and fruit, we assessed whether co-occurring frugivores provide redundant seed dispersal services in three species-rich Neotropical wetlands. Our study revealed that frugivorous fishes have generalized diets; however, large-bodied fishes had greater seed dispersal breadth than small species, in some cases, providing seed dispersal services not achieved by smaller fish species. As overfishing disproportionately affects big fishes, the extirpation of these species could cause larger secondary extinctions of plant species than the loss of small specialist frugivores. To evaluate the consequences of frugivore specialization for network stability, we extracted data from 39 published seed dispersal networks of frugivorous birds, mammals and fish (our networks) across ecosystems. Our analysis of interaction frequencies revealed low frugivore specialization and lower nestedness than analyses based on binary data (presence-absence of interactions). In that case, ecosystems may be resilient to loss of any given frugivore. However, robustness to frugivore extinction declines with specialization, such that networks composed primarily of specialist frugivores are highly susceptible to the loss of generalists. In contrast with analyses of binary data, recently developed algorithms capable of modelling interaction strengths provide opportunities to enhance our understanding of complex ecological networks by accounting for heterogeneity of frugivore-fruit interactions. © 2016 The Author(s).

  6. Undeclared baggage: Do tourists act as vectors for seed dispersal in fynbos protected areas?

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    Elizabeth H. Bouchard

    2015-10-01

    Full Text Available Encroachment by alien species is the second greatest threat to biodiversity worldwide. As South Africa’s Cape Floristic Region has a botanical endemism of nearly 70%, conservation efforts are a high priority. Estimates suggest that alien species cost the country over R6.5 billion per year. Despite significant research on alien species dispersal, the role of tourists as seed dispersers requires further exploration. To investigate the potential role tourists play in introducing alien seeds into protected areas, long-bristle brushes were used to scrape seeds off the shoes of hikers, dog walkers and cyclists, as well as the wheels of mountain bikes and dogs themselves, upon entering the Silvermine Nature Reserve section of the Table Mountain National Park in the Western Cape province, South Africa. In addition, a vegetation survey was conducted. This comprised 18 transects at various distances from the recreational paths in the park, and used a prioritisation ranking system that identified the alien species of greatest concern. It was concluded that the greatest number of alien plant species could be found along dog paths, in comparison to the hiking trails and cycling trails. This corresponded to the findings that dog walkers had the highest incidence of seeds on their shoes, suggesting that tourists were possibly dispersing seeds from their gardens. Alien species significantly covered more of the vegetation transects closer to the trails than they did in transects further into the matrix. Because more alien species were present in areas susceptible to human disturbance, the data suggest that tourists can act as vectors for alien seed dispersal. These findings emphasise the need for active tourism management in line with the South African National Parks Biodiversity Monitoring Programme in order to prevent the introduction and spread of alien species into South Africa’s protected areas. Conservation implications: Tourism is the main source of

  7. Directed seed dispersal of Piper by Carollia perspicillata and its effect on understory plant diversity and folivory.

    Science.gov (United States)

    Salazar, Diego; Kelm, Detlev H; Salazar, Diego

    2013-11-01

    Directed dispersal occurs when seeds are differentially deposited to sites where offspring survivorship is higher than at randomly chosen sites. Traditionally, characteristics of the dispersal target sites that could increase survivorship of the dispersed plants are thought to be intrinsic to the sites. If directed dispersal is constant over extended periods of time, however, it is likely that nonrandom patterns of dispersal could modify the ecological characteristics of the target site in ways that could increase survivorship and fitness of the dispersed plants. Here we report patterns of Piper diversity (richness, equitability, and similarity) and Piper folivory within plots near natural or artificial roosts of Carollia perspicillata vs. similar plots without bat roosts. Plots with bat roosts, both natural and artificial, had significantly higher Piper species diversity. Additionally, we found that plots with a higher Piper species diversity showed less specialist folivory, higher generalist folivory, and lower total herbivore leaf damage than plots with low Piper diversity. Finally, plots with bat roosts also showed less specialist folivory, lower generalist folivory, and lower total folivory when compared to plots without roosts. We propose that long-lasting nonrandom patterns of seed dispersal can change the local ecological characteristics of target sites via changes in plant diversity, and that these changes are likely to reduce the local rates of folivory and, therefore, increase seed and adult plant survivorship.

  8. Assessment of spatial discordance of primary and effective seed dispersal of European beech (Fagus sylvatica L.) by ecological and genetic methods.

    Science.gov (United States)

    Millerón, M; López de Heredia, U; Lorenzo, Z; Alonso, J; Dounavi, A; Gil, L; Nanos, N

    2013-03-01

    Spatial discordance between primary and effective dispersal in plant populations indicates that postdispersal processes erase the seed rain signal in recruitment patterns. Five different models were used to test the spatial concordance of the primary and effective dispersal patterns in a European beech (Fagus sylvatica) population from central Spain. An ecological method was based on classical inverse modelling (SSS), using the number of seed/seedlings as input data. Genetic models were based on direct kernel fitting of mother-to-offspring distances estimated by a parentage analysis or were spatially explicit models based on the genotype frequencies of offspring (competing sources model and Moran-Clark's Model). A fully integrated mixed model was based on inverse modelling, but used the number of genotypes as input data (gene shadow model). The potential sources of error and limitations of each seed dispersal estimation method are discussed. The mean dispersal distances for seeds and saplings estimated with these five methods were higher than those obtained by previous estimations for European beech forests. All the methods show strong discordance between primary and effective dispersal kernel parameters, and for dispersal directionality. While seed rain was released mostly under the canopy, saplings were established far from mother trees. This discordant pattern may be the result of the action of secondary dispersal by animals or density-dependent effects; that is, the Janzen-Connell effect. © 2013 Blackwell Publishing Ltd.

  9. Interference competition and high temperatures reduce the virulence of fig wasps and stabilize a fig-wasp mutualism.

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    Rui-Wu Wang

    2009-11-01

    Full Text Available Fig trees are pollinated by fig wasps, which also oviposit in female flowers. The wasp larvae gall and eat developing seeds. Although fig trees benefit from allowing wasps to oviposit, because the wasp offspring disperse pollen, figs must prevent wasps from ovipositing in all flowers, or seed production would cease, and the mutualism would go extinct. In Ficus racemosa, we find that syconia ('figs' that have few foundresses (ovipositing wasps are underexploited in the summer (few seeds, few galls, many empty ovules and are overexploited in the winter (few seeds, many galls, few empty ovules. Conversely, syconia with many foundresses produce intermediate numbers of galls and seeds, regardless of season. We use experiments to explain these patterns, and thus, to explain how this mutualism is maintained. In the hot summer, wasps suffer short lifespans and therefore fail to oviposit in many flowers. In contrast, cooler temperatures in the winter permit longer wasp lifespans, which in turn allows most flowers to be exploited by the wasps. However, even in winter, only in syconia that happen to have few foundresses are most flowers turned into galls. In syconia with higher numbers of foundresses, interference competition reduces foundress lifespans, which reduces the proportion of flowers that are galled. We further show that syconia encourage the entry of multiple foundresses by delaying ostiole closure. Taken together, these factors allow fig trees to reduce galling in the wasp-benign winter and boost galling (and pollination in the wasp-stressing summer. Interference competition has been shown to reduce virulence in pathogenic bacteria. Our results show that interference also maintains cooperation in a classic, cooperative symbiosis, thus linking theories of virulence and mutualism. More generally, our results reveal how frequency-dependent population regulation can occur in the fig-wasp mutualism, and how a host species can 'set the rules of the

  10. Pondberry (Lindera   melissifolia, Lauraceae) seed and seedling dispersers and predators

    Science.gov (United States)

    Andreza M. Martins; Fernanda M. Abilio; Plinio Gonçalves de Oliveira; Raquel Partelli Feltrin; Fernanda Scheffer Alves de Lima; Priscilla de O. Antonelli; Daniela Teixeira Vilela; Carl G. Smith III; Collin Tidwell; Paul Hamel; Margaret Devall; Kristina Connor; Theodor Leininger; Nathan Schiff; A. Dan Wilson

    2015-01-01

    Pondberry (Lindera melissifolia(Walter) Blume) is an endangered dioecious, clonal shrub that grows in periodically flooded forests of the southeastern United States. The probability of survival of dispersed pondberry seeds and new germinants is unknown, but few seedlings are noted in the forest. This study was undertaken to: (1) identify herbivores...

  11. Do spatially-implicit estimates of neutral migration comply with seed dispersal data in tropical forests?

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    François Munoz

    Full Text Available Neutral community models have shown that limited migration can have a pervasive influence on the taxonomic composition of local communities even when all individuals are assumed of equivalent ecological fitness. Notably, the spatially implicit neutral theory yields a single parameter I for the immigration-drift equilibrium in a local community. In the case of plants, seed dispersal is considered as a defining moment of the immigration process and has attracted empirical and theoretical work. In this paper, we consider a version of the immigration parameter I depending on dispersal limitation from the neighbourhood of a community. Seed dispersal distance is alternatively modelled using a distribution that decreases quickly in the tails (thin-tailed Gaussian kernel and another that enhances the chance of dispersal events over very long distances (heavily fat-tailed Cauchy kernel. Our analysis highlights two contrasting situations, where I is either mainly sensitive to community size (related to ecological drift under the heavily fat-tailed kernel or mainly sensitive to dispersal distance under the thin-tailed kernel. We review dispersal distances of rainforest trees from field studies and assess the consistency between published estimates of I based on spatially-implicit models and the predictions of the kernel-based model in tropical forest plots. Most estimates of I were derived from large plots (10-50 ha and were too large to be accounted for by a Cauchy kernel. Conversely, a fraction of the estimates based on multiple smaller plots (1 ha appeared too small to be consistent with reported ranges of dispersal distances in tropical forests. Very large estimates may reflect within-plot habitat heterogeneity or estimation problems, while the smallest estimates likely imply other factors inhibiting migration beyond dispersal limitation. Our study underscores the need for interpreting I as an integrative index of migration limitation which, besides

  12. Modeling fine-scale coral larval dispersal and interisland connectivity to help designate mutually-supporting coral reef marine protected areas: Insights from Maui Nui, Hawaii

    Science.gov (United States)

    Storlazzi, Curt; van Ormondt, Maarten; Chen, Yi-Leng; Elias, Edwin P. L.

    2017-01-01

    Connectivity among individual marine protected areas (MPAs) is one of the most important considerations in the design of integrated MPA networks. To provide such information for managers in Hawaii, USA, a numerical circulation model was developed to determine the role of ocean currents in transporting coral larvae from natal reefs throughout the high volcanic islands of the Maui Nui island complex in the southeastern Hawaiian Archipelago. Spatially- and temporally-varying wind, wave, and circulation model outputs were used to drive a km-scale, 3-dimensional, physics-based circulation model for Maui Nui. The model was calibrated and validated using satellite-tracked ocean surface current drifters deployed during coral-spawning conditions, then used to simulate the movement of the larvae of the dominant reef-building coral, Porites compressa, from 17 reefs during eight spawning events in 2010–2013. These simulations make it possible to investigate not only the general dispersal patterns from individual coral reefs, but also how anomalous conditions during individual spawning events can result in large deviations from those general patterns. These data also help identify those reefs that are dominated by self-seeding and those where self-seeding is limited to determine their relative susceptibility to stressors and potential roadblocks to recovery. Overall, the numerical model results indicate that many of the coral reefs in Maui Nui seed reefs on adjacent islands, demonstrating the interconnected nature of the coral reefs in Maui Nui and providing a key component of the scientific underpinning essential for the design of a mutually supportive network of MPAs to enhance conservation of coral reefs.

  13. Empty seeds are not always bad: simultaneous effect of seed emptiness and masting on animal seed predation.

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    Ramón Perea

    Full Text Available Seed masting and production of empty seeds have often been considered independently as different strategies to reduce seed predation by animals. Here, we integrate both phenomena within the whole assemblage of seed predators (both pre and post-dispersal and in two contrasting microsites (open vs. sheltered to improve our understanding of the factors controlling seed predation in a wind-dispersed tree (Ulmus laevis. In years with larger crop sizes more avian seed predators were attracted with an increase in the proportion of full seeds predated on the ground. However, for abundant crops, the presence of empty seeds decreased the proportion of full seeds predated. Empty seeds remained for a very long period in the tree, making location of full seeds more difficult for pre-dispersal predators and expanding the overall seed drop period at a very low cost (in dry biomass and allocation of C, N and P. Parthenocarpy (non-fertilized seeds was the main cause of seed emptiness whereas seed abortion was produced in low quantity. These aborted seeds fell prematurely and, thus, could not work as deceptive seeds. A proportion of 50% empty seeds significantly reduced ground seed predation by 26%. However, a high rate of parthenocarpy (beyond 50% empty seeds did not significantly reduce seed predation in comparison to 50% empty seeds. We also found a high variability and unpredictability in the production of empty seeds, both at tree and population level, making predator deception more effective. Open areas were especially important to facilitate seed survival since rodents (the main post-dispersal predators consumed seeds mostly under shrub cover. In elm trees parthenocarpy is a common event that might work as an adaptive strategy to reduce seed predation. Masting per se did not apparently reduce the overall proportion of seeds predated in this wind-dispersed tree, but kept great numbers of seeds unconsumed.

  14. The role of fleshy pericarp in seed germination and dispersal under flooded conditions in three wetland forest species

    Science.gov (United States)

    Mora, Juan P.; Smith-Ramírez, Cecilia; Zúñiga-Feest, Alejandra

    2013-01-01

    In flooded habitats, inundations affect important forest regeneration processes, such as seed dispersal and germination. The main seed dispersal mechanism used by species in Austral South American temperate swamp and riparian forests is endozoochory, which releases seeds from the fleshy pericarp. Endozoochory could be favorable or unfavorable in wetland habitats, since this mechanism exposes seeds directly to water and can, in some cases, be detrimental to germination. In this study, we studied whether or not the fleshy pericarp favors germination after the flooding period's end. Furthermore, we quantified if the number of days which the fruit was found to be floating related to its germination success. We used the seeds of three common fleshy fruit species of flooded habitats from southern Chile, the trees Luma apiculata and Rhaphithamnus spinosus, and the vine Luzuriaga radicans. We simulated flooding periods of 7, 15, 30 and 45 days submerging seeds, with and without pericarps, in water. We found that the pericarp's presence significantly increased Luma's germination success and significantly decreased that of Luzuriaga. The germination of Rhaphithamnus was low after periods of flooding in both seed treatments, with no significant differences found between them. The fruits could float for an average of one to four weeks, depending on the species, which did not relate to their germination success. These results show that germination was affected by the presence of fleshy pericarps in flooded conditions and furthermore, that flotation allows for hydrochory from one week to one month. We suggest that in swamp forests multiple seed dispersal mechanisms are advantageous, especially for fleshy-fruited species.

  15. Ants sow the seeds of global diversification in flowering plants.

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    Szabolcs Lengyel

    Full Text Available The extraordinary diversification of angiosperm plants in the Cretaceous and Tertiary periods has produced an estimated 250,000-300,000 living angiosperm species and has fundamentally altered terrestrial ecosystems. Interactions with animals as pollinators or seed dispersers have long been suspected as drivers of angiosperm diversification, yet empirical examples remain sparse or inconclusive. Seed dispersal by ants (myrmecochory may drive diversification as it can reduce extinction by providing selective advantages to plants and can increase speciation by enhancing geographical isolation by extremely limited dispersal distances.Using the most comprehensive sister-group comparison to date, we tested the hypothesis that myrmecochory leads to higher diversification rates in angiosperm plants. As predicted, diversification rates were substantially higher in ant-dispersed plants than in their non-myrmecochorous relatives. Data from 101 angiosperm lineages in 241 genera from all continents except Antarctica revealed that ant-dispersed lineages contained on average more than twice as many species as did their non-myrmecochorous sister groups. Contrasts in species diversity between sister groups demonstrated that diversification rates did not depend on seed dispersal mode in the sister group and were higher in myrmecochorous lineages in most biogeographic regions.Myrmecochory, which has evolved independently at least 100 times in angiosperms and is estimated to be present in at least 77 families and 11 000 species, is a key evolutionary innovation and a globally important driver of plant diversity. Myrmecochory provides the best example to date for a consistent effect of any mutualism on large-scale diversification.

  16. Ants sow the seeds of global diversification in flowering plants.

    Science.gov (United States)

    Lengyel, Szabolcs; Gove, Aaron D; Latimer, Andrew M; Majer, Jonathan D; Dunn, Robert R

    2009-01-01

    The extraordinary diversification of angiosperm plants in the Cretaceous and Tertiary periods has produced an estimated 250,000-300,000 living angiosperm species and has fundamentally altered terrestrial ecosystems. Interactions with animals as pollinators or seed dispersers have long been suspected as drivers of angiosperm diversification, yet empirical examples remain sparse or inconclusive. Seed dispersal by ants (myrmecochory) may drive diversification as it can reduce extinction by providing selective advantages to plants and can increase speciation by enhancing geographical isolation by extremely limited dispersal distances. Using the most comprehensive sister-group comparison to date, we tested the hypothesis that myrmecochory leads to higher diversification rates in angiosperm plants. As predicted, diversification rates were substantially higher in ant-dispersed plants than in their non-myrmecochorous relatives. Data from 101 angiosperm lineages in 241 genera from all continents except Antarctica revealed that ant-dispersed lineages contained on average more than twice as many species as did their non-myrmecochorous sister groups. Contrasts in species diversity between sister groups demonstrated that diversification rates did not depend on seed dispersal mode in the sister group and were higher in myrmecochorous lineages in most biogeographic regions. Myrmecochory, which has evolved independently at least 100 times in angiosperms and is estimated to be present in at least 77 families and 11 000 species, is a key evolutionary innovation and a globally important driver of plant diversity. Myrmecochory provides the best example to date for a consistent effect of any mutualism on large-scale diversification.

  17. Pre-dispersal seed predation in a species-rich forest community: Patterns and the interplay with determinants

    Science.gov (United States)

    Yue Xu; Zehao Shen; Daoxin Li; Qinfeng Guo

    2015-01-01

    Pre-dispersal seed predation (PDSP) is commonly observed in woody plants, and recognized as a driver of seed production variability that is critical for successful regeneration. Earlier studies on PDSP and its determinants were mostly species specific, with community- level PDSP rarely estimated; and the interactions between the temporal...

  18. Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages

    NARCIS (Netherlands)

    Caughlin, T.T.; Ferguson, J.M.; Lichstein, J.W.; Zuidema, P.A.; Bunyavejchewin, S.; Levey, D.J.

    2015-01-01

    Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing

  19. Pericarpial nectary-visiting ants do not provide fruit protection against pre-dispersal seed predators regardless of ant species composition and resource availability.

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    Priscila Andre Sanz-Veiga

    Full Text Available Extrafloral nectaries can occur in both vegetative and reproductive plant structures. In many Rubiaceae species in the Brazilian Cerrado, after corolla abscission, the floral nectary continues to secret nectar throughout fruit development originating post-floral pericarpial nectaries which commonly attract many ant species. The occurrence of such nectar secreting structures might be strategic for fruit protection against seed predators, as plants are expected to invest higher on more valuable and vulnerable parts. Here, we performed ant exclusion experiments to investigate whether the interaction with ants mediated by the pericarpial nectaries of Tocoyena formosa affects plant reproductive success by reducing the number of pre-dispersal seed predators. We also assessed whether ant protection was dependent on ant species composition and resource availability. Although most of the plants were visited by large and aggressive ant species, such as Ectatomma tuberculatum and species of the genus Camponotus, ants did not protect fruits against seed predators. Furthermore, the result of the interaction was neither related to ant species composition nor to the availability of resources. We suggest that these results may be related to the nature and behavior of the most important seed predators, like Hemicolpus abdominalis weevil which the exoskeleton toughness prevent it from being predated by most ant species. On the other hand, not explored factors, such as reward quality, local ant abundance, ant colony characteristics and/or the presence of alternative energetic sources could also account for variations in ant frequency, composition, and finally ant protective effects, highlighting the conditionality of facultative plant-ant mutualisms.

  20. Seed dispersal by fishes in tropical and temperate fresh waters: The growing evidence

    NARCIS (Netherlands)

    Horn, M.H.; Correa, S.B.; Parolin, P.; Pollux, B.J.A.; Anderson, J.T.; Lucas, C.; Widmann, P.; Tjiu, A.; Galetti, M.; Goulding, M.

    2011-01-01

    Fruit-eating by fishes represents an ancient (perhaps Paleozoic) interaction increasingly regarded as important for seed dispersal (ichthyochory) in tropical and temperate ecosystems. Most of the more than 275 known frugivorous species belong to the mainly Neotropical Characiformes (pacus, piranhas)

  1. Do Hybrid Trees Inherit Invasive Characteristics? Fruits of Corymbia torelliana X C. citriodora Hybrids and Potential for Seed Dispersal by Bees.

    Science.gov (United States)

    Wallace, Helen Margaret; Leonhardt, Sara Diana

    2015-01-01

    Tree invasions have substantial impacts on biodiversity and ecosystem functioning, and trees that are dispersed by animals are more likely to become invasive. In addition, hybridisation between plants is well documented as a source of new weeds, as hybrids gain new characteristics that allow them to become invasive. Corymbia torelliana is an invasive tree with an unusual animal dispersal mechanism: seed dispersal by stingless bees, that hybridizes readily with other species. We examined hybrids between C. torelliana and C. citriodora subsp. citriodora to determine whether hybrids have inherited the seed dispersal characteristics of C. torelliana that allow bee dispersal. Some hybrid fruits displayed the characteristic hollowness, resin production and resin chemistry associated with seed dispersal by bees. However, we did not observe bees foraging on any hybrid fruits until they had been damaged. We conclude that C. torelliana and C. citriodora subsp. citriodora hybrids can inherit some fruit characters that are associated with dispersal by bees, but we did not find a hybrid with the complete set of characters that would enable bee dispersal. However, around 20,000 hybrids have been planted in Australia, and ongoing monitoring is necessary to identify any hybrids that may become invasive.

  2. Use of perches and seed dispersal by birds in an abandoned pasture in the Porto Ferreira state park, southeastern Brazil

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    S. Athiê

    Full Text Available Abstract We investigated the efficiency of different kinds of perches in attracting seed disperser-birds and increasing the seed rain in a degraded area located in the northeast region of São Paulo State. We installed seed traps under natural perches (NPs, living trees; simple artificial perches (SAPs of 3m tall and a crossbar; elaborate artificial perches (EAPs of 7m tall and three crossbars, and in a control area. Results showed the number of bird-dispersed seeds deposited was proportional to the number of structures for perching. The NPs also have provided other resources for birds such as food and shelter. Comparing visitation between artificial perches, there was greater use of EAPs also for having more perching structures and for being taller, providing better airspace visibility for predatory birds and tyrant-flycatchers, important seed dispersers. Thus, natural and artificial perches with similar characteristics to the EAPs are the most recommended as a base or complementary method for the restoration of degraded areas near to propagules source, also contributing to the maintenance of local fauna.

  3. Functional morphology and seed anatomy of the invasive weed, benghal dayflower (Commelina benghalensis): Implications for dispersal by mourning doves

    Science.gov (United States)

    Benghal dayflower (BD) is an exotic weed that reduces yields in many agricultural crops. Potential dispersal of this weed by migratory Mourning doves was investigated in this study. Evidence shows that doves feed on BD seeds, with some birds containing hundreds of seeds. Seeds extracted from harvest...

  4. Frugivory and seed dispersal of golden lion tamarin (Leontopithecus rosalia (Linnaeus, 1766 in a forest fragment in the Atlantic Forest, Brazil

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    MJ. Lapenta

    Full Text Available The influence of the golden lion tamarin (Leontopithecus rosalia as a seed disperser was studied by monitoring two groups of tamarins from December 1998 to December 2000 (871.9 hours of observations in a forest fragment in south-east Brazil. The tamarins consumed fruits of 57 species from at least 17 families. They ingested the seeds of 39 species, and 23 of these were put to germinate in the laboratory and/or in the field. L. rosalia is a legitimate seed disperser because the seeds of all species tested germinated after ingestion, albeit some in low percentages. These primates do not show a consistent effect in final seed germination, because they benefit some species while damaging others. Feces were examined for seeds that had been preyed upon or digested.

  5. Environmental variation shifts the relationship between trees and scatterhoarders along the continuum from mutualism to antagonism.

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    Sawaya, Gina M; Goldberg, Adam S; Steele, Michael A; Dalgleish, Harmony J

    2018-05-01

    The conditional mutualism between scatterhoarders and trees varies on a continuum from mutualism to antagonism and can change across time and space, and among species. We examined 4 tree species (red oak [Quercus rubra], white oak [Quercus alba], American chestnut [Castanea dentata] and hybrid chestnut [C. dentata × Castanea mollissima) across 5 sites and 3 years to quantify the variability in this conditional mutualism. We used a published model to compare the rates of seed emergence with and without burial to the probability that seeds will be cached and left uneaten by scatterhoarders to quantify variation in the conditional mutualism that can be explained by environmental variation among sites, years, species, and seed provenance within species. All species tested had increased emergence when buried. However, comparing benefits of burial to the probability of caching by scatterhoarders indicated a mutualism in red oak, while white oak was nearly always antagonistic. Chestnut was variable around the boundary between mutualism and antagonism, indicating a high degree of context dependence in the relationship with scatterhoarders. We found that different seed provenances did not vary in their potential for mutualism. Temperature did not explain microsite differences in seed emergence in any of the species tested. In hybrid chestnut only, emergence on the surface declined with soil moisture in the fall. By quantifying the variation in the conditional mutualism that was not caused by changes in scatterhoarder behavior, we show that environmental conditions and seed traits are an important and underappreciated component of the variation in the relationship between trees and scatterhoarders. © 2018 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

  6. Fruit Size Determines the Role of Three Scatter-Hoarding Rodents as Dispersers or Seed Predators of a Fleshy-Fruited Atacama Desert Shrub

    Science.gov (United States)

    Loayza, Andrea P.; Squeo, Francisco A.

    2016-01-01

    Scatter-hoarding rodents can act as both predators and dispersers for many large-seeded plants because they cache seeds for future use, but occasionally forget them in sites with high survival and establishment probabilities. The most important fruit or seed trait influencing rodent foraging behavior is seed size; rodents prefer large seeds because they have higher nutritional content, but this preference can be counterbalanced by the higher costs of handling larger seeds. We designed a cafeteria experiment to assess whether fruit and seed size of Myrcianthes coquimbensis, an endangered desert shrub, influence the decision-making process during foraging by three species of scatter-hoarding rodents differing in body size: Abrothrix olivaceus, Phyllotis darwini and Octodon degus. We found that the size of fruits and seeds influenced foraging behavior in the three rodent species; the probability of a fruit being harvested and hoarded was higher for larger fruits than for smaller ones. Patterns of fruit size preference were not affected by rodent size; all species were able to hoard fruits within the entire range of sizes offered. Finally, fruit and seed size had no effect on the probability of seed predation, rodents typically ate only the fleshy pulp of the fruits offered and discarded whole, intact seeds. In conclusion, our results reveal that larger M. coquimbensis fruits have higher probabilities of being harvested, and ultimately of its seeds being hoarded and dispersed by scatter-hoarding rodents. As this plant has no other dispersers, rodents play an important role in its recruitment dynamics. PMID:27861550

  7. Smile, you are on camera or in a live trap! The role of mammals in dispersion of jackfruit and native seeds in Ilha Grande State Park, Brazil

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    Daniel Santana Lorenzo Raíces

    2017-11-01

    Full Text Available The alien species Artocarpus heterophyllus, originally from India, was introduced to Brazil in the colonial period and has become invasive in some areas in the Atlantic Forest. Its fruits can weigh 35 kg and produce up to 500 seeds each. In their native range they are dispersed by turtles, rodents, monkeys, wild pigs and elephants. This study aimed to investigate the influence of mammals in jackfruit predation and seed dispersal, as well as the influence of jackfruit in native plant species dispersal by mammals, in the Ilha Grande State Park, Southeastern Brazil. Seeds with and without mesocarp were tied to thread spools and checked for predation and dispersion on 37 sites. We recorded mesocarp or jackfruit seed feeding on video. Six species of mammals were recorded feeding on jackfruit, but Trinomys dimidiatus, Didelphis aurita and Cuniculus paca accounted for 92% of all records. Cuniculus paca and Trinomys dimidiatus preyed and dispersed seeds while Didelphis aurita consumed mesocarp only. Seeds with mesocarp were more preyed on than seeds without mesocarp and its consumption was lower during more intense fruit production. Hence, jackfruit production can exceed the capacity of mammals to consume its seeds in areas where jackfruit density is high. Faeces of small mammals were collected in areas with (10 grids and without jackfruits (8 grids and analysed for the presence of native seeds. Twelve small mammal species were captured in areas with and without jackfruits, but faeces of 11 species were collected. Didelphis aurita dispersed proportionally more native seeds in area without jackfruits. Our results showed that mammals are playing a negative role helping to disperse jackfruit trees, and this is occurring in different ways depending on mammal species.

  8. Simple methodologies to estimate the energy amount stored in a tree due to an explosive seed dispersal mechanism

    Science.gov (United States)

    do Carmo, Eduardo; Goncalves Hönnicke, Marcelo

    2018-05-01

    There are different forms to introduce/illustrate the energy concepts for the basic physics students. The explosive seed dispersal mechanism found in a variety of trees could be one of them. Sibipiruna trees carry out fruits (pods) who show such an explosive mechanism. During the explosion, the pods throw out seeds several meters away. In this manuscript we show simple methodologies to estimate the energy amount stored in the Sibipiruna tree due to such a process. Two different physics approaches were used to carry out this study: by monitoring indoor and in situ the explosive seed dispersal mechanism and by measuring the elastic constant of the pod shell. An energy of the order of kJ was found to be stored in a single tree due to such an explosive mechanism.

  9. Measuring short distance dispersal of Alliaria petiolata and determining potential long distance dispersal mechanisms

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    Christopher A. Loebach

    2018-03-01

    Full Text Available Introduction Alliaria petiolata, an herbaceous plant, has invaded woodlands in North America. Its ecology has been thoroughly studied, but an overlooked aspect of its biology is seed dispersal distances and mechanisms. We measured seed dispersal distances in the field and tested if epizoochory is a potential mechanism for long-distance seed dispersal. Methods Dispersal distances were measured by placing seed traps in a sector design around three seed point sources, which consisted of 15 second-year plants transplanted within a 0.25 m radius circle. Traps were placed at intervals ranging from 0.25–3.25 m from the point source. Traps remained in the field until a majority of seeds were dispersed. Eight probability density functions were fitted to seed trap counts via maximum likelihood. Epizoochory was tested as a potential seed dispersal mechanism for A. petiolata through a combination of field and laboratory experiments. To test if small mammals transport A. petiolata seeds in their fur, experimental blocks were placed around dense A. petiolata patches. Each block contained a mammal inclusion treatment (MIT and control. The MIT consisted of a wood-frame (31 × 61× 31 cm covered in wire mesh, except for the two 31 × 31 cm ends, placed over a germination tray filled with potting soil. A pan filled with bait was placed in the center of the tray. The control frame (11 × 31 × 61 cm was placed over a germination tray and completely covered in wire mesh to exclude animal activity. Treatments were in the field for peak seed dispersal. In March, trays were moved to a greenhouse and A. petiolata seedlings were counted and then compared between treatments. To determine if A. petiolata seeds attach to raccoon (Procyon lotor and white-tailed deer (Odocoileus virginianus fur, wet and dry seeds were dropped onto wet and dry fur. Furs were rotated 180 degrees and the seeds that remained attached were counted. To measure seed retention, seeds

  10. Potential roles of fish, birds, and water in swamp privet (Forestiera acuminata) seed dispersal

    Science.gov (United States)

    Susan B. Adams; Paul B. Hamel; Kristina Connor; Bryce Burke; Emile S. Gardiner; David Wise

    2007-01-01

    Forestiera acuminata (swamp privet) is a common wetland shrub/small tree native to the southeastern United States. We examined several possible dispersal avenues for the plant. We tested germination of seeds exposed to various treatments, including passage through Ictalurus punctatus (Channel Catfi sh) guts, and conducted other...

  11. The effects of seed dispersal on the simulation of long-term forest landscape change

    Science.gov (United States)

    Hong S. He; David J. Mladenoff

    1999-01-01

    The study of forest landscape change requires an understanding of the complex interactions of both spatial and temporal factors. Traditionally, forest gap models have been used to simulate change on small and independent plots. While gap models are useful in examining forest ecological dynamics across temporal scales, large, spatial processes, such as seed dispersal,...

  12. Fruit availability, frugivore satiation and seed removal in 2 primate-dispersed tree species.

    Science.gov (United States)

    Ratiarison, Sandra; Forget, Pierre-Michel

    2011-09-01

    During a mast-fruiting event we investigated spatial variability in fruit availability, consumption, and seed removal at two sympatric tree species, Manilkara bidentata and M. huberi (Sapotaceae) at Nouragues Natural Reserve, French Guiana. We addressed the question of how Manilkara density and fruits at the community level might be major causes of variability in feeding assemblages between tree species. We thus explored how the frugivore assemblages differed between forest patches with contrasting relative Manilkara density and fruiting context. During the daytime, Alouatta seniculus was more often observed in M. huberi crowns at Petit Plateau (PP) with the greatest density of Manilkara spp. and the lowest fruit diversity and availability, whereas Cebus apella and Saguinus midas were more often observed in M. bidentata crowns at both Grand Plateau (GP), with a lowest density of M. bidentata and overall greater fruit supply, and PP. Overall, nearly 53% and 15% of the M. bidentata seed crop at GP and PP, respectively, and about 47% of the M. huberi seed crop were removed, otherwise either spit out or defecated beneath trees, or dropped in fruits. Small-bodied primates concentrated fallen seeds beneath parent trees while large-bodied primate species removed and dispersed more seeds away from parents. However, among the latter, satiated A. seniculus wasted seeds under conspecific trees at PP. Variations in feeding assemblages, seed removal rates and fates possibly reflected interactions with extra-generic fruit species at the community level, according to feeding choice, habitat preferences and ranging patterns of primate species. © 2011 ISZS, Blackwell Publishing and IOZ/CAS.

  13. Quantity component of the effectiveness of seed dispersal by birds in the temperate rainforest of Chiloé, Chile

    OpenAIRE

    Salvande, Miguel; Figueroa, Javier A; Armesto, Juan J

    2011-01-01

    The quantity component of the disperser effectiveness of resident birds during the autumn-winter period has not yet been detailed in temperate rainforests of South America. In this study, the potentially frugivorous bird species in the temperate rainforests of southern Chile during the Austral autumn-winter were identified, and the quantity component of the disperser effectiveness of the birds (number of visits and number of seeds dispersed per hour) were evaluated for the tree species Luma a...

  14. CEPF Western Ghats Special Series: Frugivory and seed dispersal by the Asian Elephant Elephas maximus in the tropical forests of Nilgiri Biosphere Reserve, southern India

    Directory of Open Access Journals (Sweden)

    N. Baskaran

    2014-10-01

    Full Text Available Seed dispersal plays a potential role in plant species demographic processes. Elephants are important seed-dispersing agents. We studied frugivory and seed dispersal by Asian Elephants in the tropical deciduous and thorn forests of the Nilgiri Biosphere Reserve, southern India. We determined fruit consumption based on the presence of seeds and fruit remnants in elephant dung piles. In total, we identified seeds of eight plant species belonging to seven families in 16% out of 455 dung piles examined between 1991 and 2004. Coinciding with a peak fruiting season in the study area, seeds and other fruit parts appeared in the dung piles significantly more frequently during the dry season than in the wet seasons (southwest and northeast monsoons. Owing to differences in fruit species abundance in different habitats, there was more evidence of fruit consumption in the dry thorn than in the dry and moist deciduous forests. This corresponds with insufficient grass availability in thorn forests during the dry season and an increase in browse consumption as a supplementary diet. Seeds of Tamarindus indica and Acacia intsia were found in elephant dung more frequently than other species. Seed and fruit remnants were found in almost an equal number of dung piles of both bulls and herds.

  15. Fruit consumption and seed dispersal of Dimorphandra mollis Benth. (Leguminosae) by the lowland tapir in the cerrado of Central Brazil.

    Science.gov (United States)

    Bizerril, M X A; Rodrigues, F H G; Hass, A

    2005-08-01

    Fruit phenology observations and consumption of Dimorphandra mollis (Leguminosae) were analyzed during seven months in an area of cerrado stricto sensu. We analysed 81 fecal samples collected at six different places of lowland tapirs (Tapirus terrestris) in central Brazilian cerrado. In addition, from the feces of five tapirs at the Brasília Zoo to which fruit had been offered, seeds were collected and used in germination tests. The results suggest that the tapir is an important fruit consumer and a potential seed disperser of D. mollis. In the field, however, fruit consumption was found to be very low, probably because of both fruit palatability and the low density of frugivores, especially tapirs. The possibility that the original dispersal agents of D. mollis seeds belonged to the South American Pleistocene megafauna is discussed.

  16. Nutrient transport within and between habitats through seed dispersal processes by woolly monkeys in north-western Amazonia.

    Science.gov (United States)

    Stevenson, Pablo R; Guzmán-Caro, Diana C

    2010-11-01

    The contribution of vertebrate animals to nutrient cycling has proven to be important in various ecosystems. However, the role of large bodied primates in nutrient transport in neotropical forests is not well documented. Here, we assess the role of a population of woolly monkeys (Lagothrix lagothricha lugens) as vectors of nutrient movement through seed dispersal. We estimated total seed biomass transported by the population within and between two habitats (terra firme and flooded forests) at Tinigua Park, Colombia, and quantified potassium (K), phosphorus (P) and nitrogen (N) content in seeds of 20 plant species from both forests. Overall, the population transported an estimated minimum of 11.5 (±1.2 SD) g of potassium, 13.2 (±0.7) g of phosphorus and 34.3 (±0.1) g nitrogen, within 22.4 (±2.0) kg of seeds ha(-1) y(-1). Approximately 84% of all nutrients were deposited in the terra firme forest mostly through recycling processes, and also through translocation from the flooded forest. This type of translocation represents an important and high-quality route of transport since abiotic mechanisms do not usually move nutrients upwards, and since chemical tests show that seeds from flooded forests have comparatively higher nutrient contents. The overall contribution to nutrient movement by the population of woolly monkeys is significant because of the large amount of biomass transported, and the high phosphorus content of seeds. As a result, the phosphorus input generated by these monkeys is of the same order of magnitude as other abiotic mechanisms of nutrient transport such as atmospheric deposition and some weathering processes. Our results suggest that via seed dispersal processes, woolly monkey populations can contribute to nutrient movement in tropical forests, and may act as important nutrient input vectors in terra firme forests. © 2010 Wiley-Liss, Inc.

  17. Recruitment of hornbill-dispersed trees in hunted and logged forests of the Indian Eastern Himalaya.

    Science.gov (United States)

    Sethi, Pia; Howe, Henry F

    2009-06-01

    Hunting of hornbills by tribal communities is widespread in logged foothill forests of the Indian Eastern Himalaya. We investigated whether the decline of hornbills has affected the dispersal and recruitment of 3 large-seeded tree species. We hypothesized that 2 low-fecundity tree species, Chisocheton paniculatus and Dysoxylum binectariferum (Meliaceae) bearing arillate fruits, are more dispersal limited than a prolifically fruiting drupaceous tree Polyalthia simiarum (Annonaceae), which has potential dispersers other than hornbills. We estimated the abundance of large avian frugivores during the fruiting season along transects in 2 protected and 2 disturbed forests. We compared recruitment of the tree species near (Hornbills (Anthracoceros albirostris) were significantly lower in disturbed forests, but sites did not differ in abundances of the Mountain Imperial Pigeon (Ducula badia). Overall, tree species showed more severely depressed recruitment of seedlings (77% fewer) and juveniles (69% fewer) in disturbed than in protected forests. In disturbed forests, 93% fewer seedlings of C. paniculatus were beyond parental crowns, and a high number of all seedlings (42%) accumulated directly under reproductive adults. In contrast, D. binectariferum and P. simiarum were recruitment rather than dispersal limited, with fewer dispersed seedlings surviving in disturbed than in protected forests. Results are consistent with the idea that disturbance disrupts mutualisms between hornbills and some large-seeded food plants, with the caveat that role redundancy within even small and specialized disperser assemblages renders other tree species less vulnerable to loss of regular dispersal agents. ©2009 Society for Conservation Biology.

  18. Seed dormancy and germination changes of snowbed species under climate warming: the role of pre- and post-dispersal temperatures

    Science.gov (United States)

    Bernareggi, Giulietta; Carbognani, Michele; Mondoni, Andrea; Petraglia, Alessandro

    2016-01-01

    Background and Aims Climate warming has major impacts on seed germination of several alpine species, hence on their regeneration capacity. Most studies have investigated the effects of warming after seed dispersal, and little is known about the effects a warmer parental environment may have on germination and dormancy of the seed progeny. Nevertheless, temperatures during seed development and maturation could alter the state of dormancy, affecting the timing of emergence and seedling survival. Here, the interplay between pre- and post-dispersal temperatures driving seed dormancy release and germination requirements of alpine plants were investigated. Methods Three plant species inhabiting alpine snowbeds were exposed to an artificial warming treatment (i.e. +1·5 K) and to natural conditions in the field. Seeds produced were exposed to six different periods of cold stratification (0, 2, 4, 8, 12 and 20 weeks at 0 °C), followed by four incubation temperatures (5, 10, 15 and 20 °C) for germination testing. Key Results A warmer parental environment produced either no or a significant increase in germination, depending on the duration of cold stratification, incubation temperatures and their interaction. In contrast, the speed of germination was less sensitive to changes in the parental environment. Moreover, the effects of warming appeared to be linked to the level of (physiological) seed dormancy, with deeper dormant species showing major changes in response to incubation temperatures and less dormant species in response to cold stratification periods. Conclusions Plants developed under warmer climates will produce seeds with changed germination responses to temperature and/or cold stratification, but the extent of these changes across species could be driven by seed dormancy traits. Transgenerational plastic adjustments of seed germination and dormancy shown here may result from increased seed viability, reduced primary and secondary dormancy state, or both, and

  19. Dispersal limitation induces long-term biomass collapse in overhunted Amazonian forests.

    Science.gov (United States)

    Peres, Carlos A; Emilio, Thaise; Schietti, Juliana; Desmoulière, Sylvain J M; Levi, Taal

    2016-01-26

    Tropical forests are the global cornerstone of biological diversity, and store 55% of the forest carbon stock globally, yet sustained provisioning of these forest ecosystem services may be threatened by hunting-induced extinctions of plant-animal mutualisms that maintain long-term forest dynamics. Large-bodied Atelinae primates and tapirs in particular offer nonredundant seed-dispersal services for many large-seeded Neotropical tree species, which on average have higher wood density than smaller-seeded and wind-dispersed trees. We used field data and models to project the spatial impact of hunting on large primates by ∼ 1 million rural households throughout the Brazilian Amazon. We then used a unique baseline dataset on 2,345 1-ha tree plots arrayed across the Brazilian Amazon to model changes in aboveground forest biomass under different scenarios of hunting-induced large-bodied frugivore extirpation. We project that defaunation of the most harvest-sensitive species will lead to losses in aboveground biomass of between 2.5-5.8% on average, with some losses as high as 26.5-37.8%. These findings highlight an urgent need to manage the sustainability of game hunting in both protected and unprotected tropical forests, and place full biodiversity integrity, including populations of large frugivorous vertebrates, firmly in the agenda of reducing emissions from deforestation and forest degradation (REDD+) programs.

  20. Pre-Dispersal Seed Predation in a Species-Rich Forest Community: Patterns and the Interplay with Determinants.

    Directory of Open Access Journals (Sweden)

    Yue Xu

    Full Text Available Pre-dispersal seed predation (PDSP is commonly observed in woody plants, and recognized as a driver of seed production variability that is critical for successful regeneration. Earlier studies on PDSP and its determinants were mostly species specific, with community-level PDSP rarely estimated; and the interactions between the temporal variability of seed production and PDSP remain elusive. In this study, the community seed rain of woody plants in a mixed evergreen-deciduous broadleaf forest was monitored for seven years. We examined predation on collected seeds and analyzed the determinants of PDSP. PDSP was recorded in 17 out of 44 woody plant species, and three-quarters of PDSP was due to insect predators. Annual seed production varied substantially at community level, reversely linked with the temporal variation of PDSP rate. The PDSP rate was biased regarding fruit types, and being significantly correlated with seed mass when using phylogenetic independent contrasts (PICs or without taking into account phylogenetic relations, especially for nuts. PDSP rate was also negatively correlated with seed density, showing a threshold-related predator satiation effect. The community-level PDSP rate was primarily determined by tree height, fruit type, and interannual variation of seed production and seed mass. Our analysis revealed a causal link between seed production and the dynamics of PDSP rate at the community level. The predator satiation effect was primarily contributed by the dominant species, whereas the rare species seemed to apply a distinct "hide-and-seek" strategy to control the risk of PDSP. The mechanistic difference of seed production between the common and rare species can shed new light on species coexistence and community assembly. Long-term monitoring of both seed rain and seed predation is required for understanding the ecological and evolutionary implications of species regeneration strategies in a species-rich forest community.

  1. The impact of anthropogenic food supply on fruit consumption by dusky-legged guan (Penelope obscura Temminck, 1815: potential effects on seed dispersal in an Atlantic forest area

    Directory of Open Access Journals (Sweden)

    J. Vasconcellos-Neto

    Full Text Available Abstract Frugivorous birds are important seed dispersers and influence the recruitment of many plant species in the rainforest. The efficiency of this dispersal generally depends on environment quality, bird species, richness and diversity of resources, and low levels of anthropogenic disturbance. In this study, we compared the sighting number of dusky-legged guans (Penelope obscura by km and their movement in two areas of Serra do Japi, one around the administrative base (Base where birds received anthropogenic food and a pristine area (DAE with no anthropogenic resource. We also compared the richness of native seeds in feces of birds living in these two areas. Although the abundance of P. obscura was higher in the Base, these individuals moved less, dispersed 80% fewer species of plants and consumed 30% fewer seeds than individuals from DAE. The rarefaction indicated a low richness in the frugivorous diet of birds from the Base when compared to the populations from DAE. We conclude that human food supply can interfere in the behavior of these birds and in the richness of native seeds dispersed.

  2. Effects of gut passage, feces, and seed handling on latency and rate of germination in seeds consumed by capuchins (Cebus capucinus).

    Science.gov (United States)

    Valenta, Kim; Fedigan, Linda M

    2009-04-01

    One of the key measures of the effectiveness of primary seed dispersal by animals is the quality of seed dispersal (Schupp: Plant Ecol 107/108 [1993] 15-29). We present data on quality of seed dispersal by two groups of white-faced capuchins (Cebus capucinus) in Costa Rica to test the hypothesis that capuchin seed handling results in effective primary dispersal for some fruit species they consume. We examined seed handling for 27 plant species, and germination rates of 18 species consumed by capuchins. For five of the most commonly swallowed seed species, we determined germination rates and average time to germination (latency) for seeds ingested and defecated by capuchins and compared these to seeds removed directly from fruit and planted. For the same five species, we compared germination rates and latency for passed seeds planted in capuchin feces to those cleaned of feces and planted in soil. For three of five species, differences in proportion of germinated seeds were significantly higher for gut passed seeds than for controls. For four of five species, germination latency was significantly faster for gut passed seeds than for controls. Feces had either no effect on seed germination rate or precluded germination. Data presented here support the hypothesis that white-faced capuchins are effective primary dispersers.

  3. High-resolution GPS tracking reveals habitat selection and the potential for long-distance seed dispersal by Madagascan flying foxes Pteropus rufus

    Directory of Open Access Journals (Sweden)

    Ryszard Oleksy

    2015-01-01

    Full Text Available Long-distance seed dispersal can be important for the regeneration of forested habitats, especially in regions where deforestation has been severe. Old World fruit bats (Pteropodidae have considerable potential for long-distance seed dispersal. We studied the movement patterns and feeding behaviour of the endemic Madagascan flying fox Pteropus rufus, in Berenty Reserve, southeast Madagascar. Between July and September 2012 (the dry season nine males and six females were tagged with customised GPS loggers which recorded fixes every 2.5 min between 18.00 and 06.00 h. The combined home range of all of the tagged bats during 86 nights exceeded 58,000 ha. Females had larger home ranges and core foraging areas and foraged over longer distances (average 28.1 km; median 26.7 km than males (average 15.4 km; median 9.5 km. Because the study was conducted during the gestation period, the increased energy requirements of females may explain their greater mean foraging area. Compositional analysis revealed that bats show strong preferences for overgrown sisal (Agave sisalana plantations (a mix of shrub, trees and sisal plants and remnant riverside forest patches. Sisal nectar and pollen were abundant food sources during the tracking period and this probably contributed to the selective use of overgrown sisal plantations. The bats also ate large quantities of figs (Ficus grevei during the study, and dispersed seeds of this important pioneer species. The bats flew at an average speed of 9.13 m/s, perhaps to optimise gliding performance. The study confirms that P. rufus has the potential to be a long-distance seed disperser, and is able to fly over a large area, often crossing cleared parts of its habitat. It potentially plays an important role in the regeneration of threatened forest habitats in this biodiversity hotspot.

  4. Meta-analysis of the effects of forest fragmentation on interspecific interactions.

    Science.gov (United States)

    Magrach, Ainhoa; Laurance, William F; Larrinaga, Asier R; Santamaria, Luis

    2014-10-01

    Forest fragmentation dramatically alters species persistence and distribution and affects many ecological interactions among species. Recent studies suggest that mutualisms, such as pollination and seed dispersal, are more sensitive to the negative effects of forest fragmentation than antagonisms, such as predation or herbivory. We applied meta-analytical techniques to evaluate this hypothesis and quantified the relative contributions of different components of the fragmentation process (decreases in fragment size, edge effects, increased isolation, and habitat degradation) to the overall effect. The effects of fragmentation on mutualisms were primarily driven by habitat degradation, edge effects, and fragment isolation, and, as predicted, they were consistently more negative on mutualisms than on antagonisms. For the most studied interaction type, seed dispersal, only certain components of fragmentation had significant (edge effects) or marginally significant (fragment size) effects. Seed size modulated the effect of fragmentation: species with large seeds showed stronger negative impacts of fragmentation via reduced dispersal rates. Our results reveal that different components of the habitat fragmentation process have varying impacts on key mutualisms. We also conclude that antagonistic interactions have been understudied in fragmented landscapes, most of the research has concentrated on particular types of mutualistic interactions such as seed dispersal, and that available studies of interspecific interactions have a strong geographical bias (arising mostly from studies carried out in Brazil, Chile, and the United States). © 2014 Society for Conservation Biology.

  5. Potential role of frugivorous birds (Passeriformes) on seed dispersal of six plant species in a restinga habitat, southeastern Brazil.

    Science.gov (United States)

    Gomes, Verônica Souza da Mota; Correia, Maria Célia Rodrigues; de Lima, Heloisa Alves; Alves, Maria Alice S

    2008-03-01

    Restingas are considered stressful habitats associated with the Brazilian Atlantic forest, and their ecological interactions are poorly known. The goal of the present study was to determine the potential role of frugivorous birds as seed dispersers in a restinga habitat. Data were collected in Parque Nacional da Restinga de Jurubatiba, southeastern Brazil, where the main physiognomy (Open Clusia Formation) is characterized by the presence of patches of vegetation covering 20 to 48 % of the sandy soil and reaching a height of 5 m. Birds were captured with mist nets (12 x 2.5 m; 36 mm mesh; 1,680 net-hrs) and had their fecal and regurgitate samples inspected for seeds. Six plant species found in these bird samples were studied. The germination of seeds obtained from plants was compared to those from the birds. Both groups of seeds were set on Petri dishes at room temperature and washed when infected with fungi. In general, there was no effect on germination rate, and the effect on germination speed was negative. Germination of seeds from Pilosocereus arrabidae treated by the birds seemed to be influenced by storage of defecated seeds, while few Miconia cinnamomifolia seeds both from plants and from birds germinated. Ocotea notata presented a great variation in time to the onset of germination, perhaps an advantage against dissecation. Aechmea nudicaulis, Clusia hilariana and Erythroxylum subsessile probably take advantage of the arrival to favorable microhabitats, not by the gut effect on the seeds. All plant species studied are numerically important for the community and some of them are main actors in the succession of vegetation patches. Among the birds, Mimus gilvus is an important resident species, endemic to restingas in Brazil, while Turdus amaurochalinus is a visitor and may be important for plants that fructify during its passage by the study site. Although the effect of pulp removal was only tested for one species (Achmea nudicaulis) in the present study

  6. Evidence for a trade-off strategy in stone oak (Lithocarpus seeds between physical and chemical defense highlights fiber as an important antifeedant.

    Directory of Open Access Journals (Sweden)

    Xi Chen

    Full Text Available Trees in the beech or oak family (Fagaceae have a mutualistic relationship with scatter-hoarding rodents. Rodents obtain nutrients and energy by consuming seeds, while providing seed dispersal for the tree by allowing some cached seeds to germinate. Seed predation and caching behavior of rodents is primarily affected by seed size, mechanical protection, macronutrient content, and chemical antifeedants. To enhance seed dispersal, trees must optimize trade-offs in investment between macronutrients and antifeedants. Here, we examine this important chemical balance in the seeds of tropical stone oak species with two substantially different fruit morphologies. These two distinct fruit morphologies in Lithocarpus differ in the degree of mechanical protection of the seed. For 'acorn' fruit, a thin exocarp forms a shell around the seed while for 'enclosed receptacle' (ER fruit, the seed is embedded in a woody receptacle. We compared the chemical composition of numerous macronutrient and antifeedant in seeds from several Lithocarpus species, focusing on two pairs of sympatric species with different fruit morphologies. We found that macronutrients, particularly total non-structural carbohydrate, was more concentrated in seeds of ER fruits while antifeedants, primarily fibers, were more concentrated in seeds of acorn fruits. The trade-off in these two major chemical components was more evident between the two sympatric lowland species than between two highland species. Surprisingly, no significant difference in overall tannin concentrations in the seeds was observed between the two fruit morphologies. Instead, the major trade-off between macronutrients and antifeedants involved indigestible fibers. Future studies of this complex mutualism should carefully consider the role of indigestible fibers in the foraging behavior of scatter-hoarding rodents.

  7. Gene regulation in seeds : insights into translational dynamics

    NARCIS (Netherlands)

    Bai, B.

    2016-01-01

    Seeds are unique structures in the plant life cycle. The variation in the timing of seed maturation, dispersion, and the establishment of seed dormancy and longevity, increases the chances of plant survival and enlarge the distance that plants could disperse in the natural habitat. Seeds contain

  8. The choice of process parameters to obtain a stable dispersion system of plant-based bioactivated dicotyledonous seeds

    Directory of Open Access Journals (Sweden)

    L. A. Samofalova

    2016-01-01

    Full Text Available The article dealswith the search for the unification of technological approaches to increase the efficiency of separation of the protein complex and stability of the plant foundations from seed dicotyledonous economically important crops of soybean, hemp, buckwheat. Uneven localization of nitrogenous substances in the seed largely determines the accessibility of protein complexes for extraction. Natural fermentation of spare proteins in cellular structures when the germination process starts leads to the accumulation of soluble nitrogen, and the change in the salt composition of protoplasm facilitates the transition in the solution of insoluble complexes in the form of colloids. It is shown that fine grinding of dry seeds increases the efficiency of extraction by 1.3–1.6 times, while rough grinding increases bioactivity by 1.6–1.8 times. The dispersion containing 8.1±0.7% of dry matter at buckwheat bases and 9.5±1,3% at hemp and soy bases with the water ratio 1:4 to 1:7 satisfy the requirements of taste sensations and fullness of the chemical composition. Based on the results of the extraction of protein of buckwheat seeds the conclusion has been drawn that there is a need for a differentiated approach to selecting conditions for the creation of food framework. Taking into consideration the fact that the amount of calcium in buckwheat seeds is17–25 times smaller than in oil seeds and the quantity of phosphorus is 1.6–2 times smaller, the contribution of electrostatic forces in the protein solubility is small and the additional actions to activate the protein complex are required. To predict the properties of vegetable bases of bioactivated soybean seeds and hemp, the central composite uniform-rotatable planning was applied and the full factorial experiment with factorial scheme 3×3×3 (33 was selected. The preferred combination of values of the input parameters X1, X2, X3 was discovered. They provide for the maximum of Y

  9. Mineral Licks Attract Neotropical Seed-Dispersing Bats

    International Nuclear Information System (INIS)

    Voigt, Ch.C.; Dechmann, D.K.N.; Dechmann, D.K.N.; Kunz, Th.H.; Bender, J.; Rinehart, B.J.; Michener, R.H.

    2007-01-01

    Unlike most terrestrial mammals, female bats must supply their offspring with all required nutrients until pups achieve virtually adult size, at which time they are able to fly and become independent. Access to nutrients may be especially challenging for reproductively active females in mineral-poor landscapes such as tropical rain forests. We hypothesized that pregnant and lactating females from tropical landscapes acquire essential nutrients from locally-available mineral licks. We captured ten times as many bats at mineral licks than at control sites in a lowland rain forest in eastern Ecuador. Among bats captured at mineral licks, the sex ratio was heavily biased toward females, and a significantly higher portion of females captured at these sites, compared to control sites, were reproductively active (pregnant and lactating). Enrichment of N 15 in relation to N 14 in wing tissue indicated that bats captured at mineral licks were mostly fruit-eating species. Given the high visitation rates of reproductive active females at mineral licks, it is likely that mineral licks are important for fruit-eating female bats as a mineral source during late pregnancy and lactation. By sustaining high population densities of fruit-eating bats that disperse seeds, mineral licks may have an indirect influence on local plant species richness.

  10. Fine-scale spatial genetic structure in predominantly selfing plants with limited seed dispersal: A rule or exception?

    Directory of Open Access Journals (Sweden)

    Sergei Volis

    2016-04-01

    Full Text Available Gene flow at a fine scale is still poorly understood despite its recognized importance for plant population demographic and genetic processes. We tested the hypothesis that intensity of gene flow will be lower and strength of spatial genetic structure (SGS will be higher in more peripheral populations because of lower population density. The study was performed on the predominantly selfing Avena sterilis and included: (1 direct measurement of dispersal in a controlled environment; and (2 analyses of SGS in three natural populations, sampled in linear transects at fixed increasing inter-plant distances. We found that in A. sterilis major seed dispersal is by gravity in close (less than 2 m vicinity of the mother plant, with a minor additional effect of wind. Analysis of SGS with six nuclear SSRs revealed a significant autocorrelation for the distance class of 1 m only in the most peripheral desert population, while in the two core populations with Mediterranean conditions, no genetic structure was found. Our results support the hypothesis that intensity of SGS increases from the species core to periphery as a result of decreased within-population gene flow related to low plant density. Our findings also show that predominant self-pollination and highly localized seed dispersal lead to SGS at a very fine scale, but only if plant density is not too high.

  11. Are post-dispersed seeds of Eucalyptus globulus predated in the introduced range? Evidence from an experiment in Portugal

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    E. Deus

    2018-04-01

    Full Text Available Plantations of Eucalyptus globulus Labill. have been expanding rapidly worldwide. The species is considered invasive in several regions. While in the native range, post-dispersal seed predation is known to severely limit eucalypt recruitment, there is no experimental evidence of seed predation in the introduced range. We hypothesised that E. globulus seeds largely escape predation in Portugal, which may explain its prolific recruitment in some locations. We tested this hypothesis in central Portugal by exposing E. globulus seeds to the local fauna. For comparison purposes, we also used seeds from locally common species: Acacia dealbata Link (alien, larger, elaiosome-bearing seeds and Cistus salviifolius L. (native, similarly sized seeds. We installed 30 feeding stations across three study sites, each one dominated by one study species. Each feeding station featured four feeders with different animal-access treatments: invertebrates; vertebrates; full access; no access (control. We placed five seeds of each plant species every day in each feeder and registered the number of seeds missing, eaten and elaiosome detached over 9 summer days. Eucalyptus globulus seeds were highly attractive to fauna in the three sites. Nearly half of E. globulus seeds were predated or removed, thus contradicting our hypothesis. Surprisingly, E. globulus and A. dealbata seeds were used by animals in similar proportions and C. salviifolius seeds were the least preferred. Vertebrates were the predominant seed predators and preferred the alien seeds. Invertebrates used all seed species in similar proportions. We found spatial variation regarding the predominant type of seed predators and the levels of seed predation according to the following patterns: predominance of vertebrates; predominance of invertebrates; negligible seed predator activity. Locations with negligible seed predation were abundant and scattered across the study area. Such spatial variation may

  12. Humans as long-distance dispersers of rural plant communities.

    Directory of Open Access Journals (Sweden)

    Alistair G Auffret

    Full Text Available Humans are known for their capacity to disperse organisms long distances. Long-distance dispersal can be important for species threatened by habitat destruction, but research into human-mediated dispersal is often focused upon few and/or invasive species. Here we use citizen science to identify the capacity for humans to disperse seeds on their clothes and footwear from a known species pool in a valuable habitat, allowing for an assessment of the fraction and types of species dispersed by humans in an alternative context. We collected material from volunteers cutting 48 species-rich meadows throughout Sweden. We counted 24,354 seeds of 197 species, representing 34% of the available species pool, including several rare and protected species. However, 71 species (36% are considered invasive elsewhere in the world. Trait analysis showed that seeds with hooks or other appendages were more likely to be dispersed by humans, as well as those with a persistent seed bank. More activity in a meadow resulted in more dispersal, both in terms of species and representation of the source communities. Average potential dispersal distances were measured at 13 km. We consider humans capable seed dispersers, transporting a significant proportion of the plant communities in which they are active, just like more traditional vectors such as livestock. When rural populations were larger, people might have been regular and effective seed dispersers, and the net rural-urban migration resulting in a reduction in humans in the landscape may have exacerbated the dispersal failure evident in declining plant populations today. With the fragmentation of habitat and changes in land use resulting from agricultural change, and the increased mobility of humans worldwide, the dispersal role of humans may have shifted from providers of regular local and landscape dispersal to providers of much rarer long-distance and regional dispersal, and international invasion.

  13. Did fleshy fruit pulp evolve as a defence against seed loss rather ...

    Indian Academy of Sciences (India)

    dispersers. Most seed dispersal studies are ecological and examine the role of fruit pulp in promoting seed dispersal. ... Introduction. Endozoochory, the interaction between fleshy-fruited plants ... adaptations for seed defence may have led to the evolution ..... Eriksson O and Bremer B 1992 Pollination systems, dispersal.

  14. Seed dispersal turns an experimental plantation on degraded land into a novel forest in urban northern Puerto Rico

    Science.gov (United States)

    Oscar Abelleira; Elvia J. Meléndez Ackerman; Diana García Montiel; John A. Parrotta

    2015-01-01

    Planting tree species with desirable traits may catalyze forest regeneration in increasingly common degraded lands by restoring soil properties and attracting seed dispersers. We sampled forest regeneration in an experimental plantation of Albizia lebbek, an introduced N-fixing species, on a degraded pasture in northern Puerto Rico, 27 years after its establishment. We...

  15. Resistance of Benghal Dayflower (Commelina benghalensis) Seeds to Harsh Environments and the Implications for Dispersal by Mourning Doves (Zenaida macroura) in Georgia, U.S.A.

    Science.gov (United States)

    The potential dispersal of Benghal dayflower seeds by mourning doves was studied in southern Georgia, U.S.A. The gut contents (both crop and gizzard) of mourning doves harvested in the autumn months were investigated to determine if mourning doves fed on Benghal dayflower and whether seeds can surv...

  16. Phenology, seed dispersal and difficulties in natural recruitment of the canopy tree Pachira quinata (Malvaceae

    Directory of Open Access Journals (Sweden)

    Maria Clara Castellanos

    2011-06-01

    Full Text Available Life history and recruitment information of tropical trees in natural populations is scarce even for important commercial species. This study focused on a widely exploited Neotropical canopy species, Pachiraquinata (Malvaceae, at the southernmost, wettest limit of its natural distribution, in the Colombian Amazonia. We studied phenological patterns, seed production and natural densities; assessed the importance of seed dispersal and density-dependent effects on recruitment, using field experiments. At this seasonal forest P. quinata was overrepresented by large adult trees and had very low recruitment caused by the combination of low fruit production, high seed predation and very high seedling mortality under continuous canopies mostly due to damping off pathogens. There was no evidence of negative distance or density effects on recruitment, but a clear requirement of canopy gaps for seedling survival and growth, where pathogen incidence was drastically reduced. In spite of the strong dependence on light for survival of seedlings, seeds germinated readily in the dark. At the study site, the population of P. quinata appeared to be declining, likely because recruitment depended on the rare combination of large gap formation with the presence of reproductive trees nearby. The recruitment biology of this species makes it very vulnerable to any type of logging in natural populations. Rev. Biol. Trop. 59 (2: 921-933. Epub 2011 June 01

  17. Seed development and carbohydrates

    NARCIS (Netherlands)

    Wittich, P.E.

    1998-01-01

    Seeds assure the plant the onset of a next generation and a way of dispersal. They consist of endosperm and an embryo (originating from gametophytic tissue), enveloped by a seed coat (sporophytic tissue). Plants generate different types of seeds. For instance, the endosperm may either be

  18. An Analysis of the Mutual Fund Industry: Mutual Fund Investors, Mutual Fund Managers and Mutual Fund Companies

    OpenAIRE

    Fang, Jieyan

    2012-01-01

    In this dissertation I investigate the mutual fund industry, especially the three most important participants within this industry: mutual fund investors, mutual fund companies and mutual fund managers. The main research questions of this dissertation are: 1. Does rapid trading exist among German equity mutual fund investors? What are the determinants of rapid trading? Does rapid trading have a negative impact on mutual fund performance? 2. Do mutual fund investors, as a whole, have...

  19. Spanish juniper gain expansion opportunities by counting on a functionally diverse dispersal assemblage community.

    Science.gov (United States)

    Escribano-Ávila, Gema; Pías, Beatriz; Sanz-Pérez, Virginia; Virgós, Emilio; Escudero, Adrián; Valladares, Fernando

    2013-10-01

    Seed dispersal is typically performed by a diverse array of species assemblages with different behavioral and morphological traits which determine dispersal quality (DQ, defined as the probability of recruitment of a dispersed seed). Fate of ecosystems to ongoing environmental changes is critically dependent on dispersal and mainly on DQ in novel scenarios. We assess here the DQ, thus the multiplicative effect of germination and survival probability to the first 3 years of life, for seeds dispersed by several bird species (Turdus spp.) and carnivores (Vulpes vulpes, Martes foina) in mature woodland remnants of Spanish juniper (Juniperus thurifera) and old fields which are being colonized by this species. Results showed that DQ was similar in mature woodlands and old fields. Germination rate for seeds dispersed by carnivores (11.5%) and thrushes (9.12%) was similar, however, interacted with microhabitat suitability. Seeds dispersed by carnivores reach the maximum germination rate on shrubs (16%), whereas seeds dispersed by thrushes did on female juniper canopies (15.5) indicating that each group of dispersers performed a directed dispersal. This directional effect was diluted when survival probability was considered: thrushes selected smaller seeds which had higher mortality in the seedling stage (70%) in relation to seedlings dispersed by carnivores (40%). Overall, thrushes resulted low-quality dispersers which provided a probability or recruitment of 2.5%, while a seed dispersed by carnivores had a probability of recruitment of 6.5%. Our findings show that generalist dispersers (i.e., carnivores) can provide a higher probability of recruitment than specialized dispersers (i.e., Turdus spp.). However, generalist species are usually opportunistic dispersers as their role as seed dispersers is dependent on the availability of trophic resources and species feeding preferences. As a result, J. thurifera dispersal community is composed by two functional groups of

  20. Genetic structure and seed-mediated dispersal rates of an endangered shrub in a fragmented landscape: a case study for Juniperus communis in northwestern Europe

    Directory of Open Access Journals (Sweden)

    Adriaenssens Sandy

    2011-08-01

    Full Text Available Abstract Background Population extinction risk in a fragmented landscape is related to the differential ability of the species to spread its genes across the landscape. The impact of landscape fragmentation on plant population dynamics will therefore vary across different spatial scales. We quantified successful seed-mediated dispersal of the dioecious shrub Juniperus communis in a fragmented landscape across northwestern Europe by using amplified fragment length polymorphism (AFLP markers. Furthermore we investigated the genetic diversity and structure on two spatial scales: across northwestern Europe and across Flanders (northern Belgium. We also studied whether seed viability and populations size were correlated with genetic diversity. Results Unexpectedly, estimated seed-mediated dispersal rates were quite high and ranged between 3% and 14%. No population differentiation and no spatial genetic structure were detected on the local, Flemish scale. A significant low to moderate genetic differentiation between populations was detected at the regional, northwest European scale (PhiPT = 0.10. In general, geographically nearby populations were also genetically related. High levels of within-population genetic diversity were detected but no correlation was found between any genetic diversity parameter and population size or seed viability. Conclusions In northwestern Europe, landscape fragmentation has lead to a weak isolation-by-distance pattern but not to genetic impoverishment of common juniper. Substantial rates of successful migration by seed-mediated gene flow indicate a high dispersal ability which could enable Juniperus communis to naturally colonize suitable habitats. However, it is not clear whether the observed levels of migration will suffice to counterbalance the effects of genetic drift in small populations on the long run.

  1. Ecological, historical and evolutionary determinants of modularity in weighted seed-dispersal networks

    DEFF Research Database (Denmark)

    Schleuning, Matthias; Ingmann, Lili; Strauß, Rouven

    2014-01-01

    Modularity is a recurrent and important property of bipartite ecological networks. Although well-resolved ecological networks describe interaction frequencies between species pairs, modularity of bipartite networks has been analysed only on the basis of binary presence-absence data. We employ a new...... algorithm to detect modularity in weighted bipartite networks in a global analysis of avian seed-dispersal networks. We define roles of species, such as connector values, for weighted and binary networks and associate them with avian species traits and phylogeny. The weighted, but not binary, analysis...... identified a positive relationship between climatic seasonality and modularity, whereas past climate stability and phylogenetic signal were only weakly related to modularity. Connector values were associated with foraging behaviour and were phylogenetically conserved. The weighted modularity analysis...

  2. Extreme reproduction and survival of a true cliffhanger: the endangered plant, Borderea chouardii (Dioscoreaceae)

    DEFF Research Database (Denmark)

    García, M. B.; Espadaler, Xavier; Olesen, Jens Mogens

    2012-01-01

    self-sown seeds, and 1/3 was dispersed by ants, which gathered the seeds with their oil-rich elaiosome. Gravity played a minor role to dispersal. Both ant dispersal and self-sowing resulted in the same survival rate of seedlings. A double mutualism is a risky reproductive strategy, but B. chouardii...... aspects is extreme, especially the unusual double mutualistic role of ants as both pollinators and dispersers. We made a 2-year pollination census and four years of seed-dispersal experiments, recording flower visitors and dispersal rates. Fruit and seed set, self-sowing of seeds, seedling recruitment......, and fate of seedlings from seeds sowed by different agents were scored over a period of 17 years. The ants Lasius grandis and L. cinereus were the main pollinators, whereas another ant Pheidole pallidula dispersed seeds. Thus ants functioned as double mutualists. Two thirds of all new seedlings came from...

  3. Long-term persistence of pioneer species in tropical forest soil seed banks

    Energy Technology Data Exchange (ETDEWEB)

    Dalling, J W; Brown, T A

    2008-10-05

    In tropical forests, pioneer species regenerate from seeds dispersed directly into canopy gaps, and from seeds that persisted in soil seed banks before gap formation. However, life-history models suggest that selection for long-term persistence of seeds in soil should be weak, as persistence incurs a fitness cost resulting from prolonged generation time. We use a carbon dating technique to provide the first direct measurements of seed persistence in undisturbed tropical forest seed banks. We show that seeds germinate successfully from surface soil microsites up to 38 years after dispersal. Decades-long persistence may be common in pioneers with relatively large mass, and appears to be unrelated to specific regeneration requirements. In Croton billbergianus, a sub-canopy tree that recruits in abundant small gaps, long-term persistence is associated with short-distance ballistic seed dispersal. In Trema micrantha, a canopy tree with widespread dispersal, persistence is associated with a requirement for large gaps that form infrequently in old-growth forest.

  4. Retention time variability as a mechanism for animal mediated long-distance dispersal.

    Directory of Open Access Journals (Sweden)

    Vishwesha Guttal

    Full Text Available Long-distance dispersal (LDD events, although rare for most plant species, can strongly influence population and community dynamics. Animals function as a key biotic vector of seeds and thus, a mechanistic and quantitative understanding of how individual animal behaviors scale to dispersal patterns at different spatial scales is a question of critical importance from both basic and applied perspectives. Using a diffusion-theory based analytical approach for a wide range of animal movement and seed transportation patterns, we show that the scale (a measure of local dispersal of the seed dispersal kernel increases with the organisms' rate of movement and mean seed retention time. We reveal that variations in seed retention time is a key determinant of various measures of LDD such as kurtosis (or shape of the kernel, thinkness of tails and the absolute number of seeds falling beyond a threshold distance. Using empirical data sets of frugivores, we illustrate the importance of variability in retention times for predicting the key disperser species that influence LDD. Our study makes testable predictions linking animal movement behaviors and gut retention times to dispersal patterns and, more generally, highlights the potential importance of animal behavioral variability for the LDD of seeds.

  5. Validating Farmers' Indigenous Social Networks for Local Seed Supply in Central Rift Valley of Ethiopia

    NARCIS (Netherlands)

    Seboka, B.; Deressa, A.

    2000-01-01

    Indigenous social networks of Ethiopian farmers participate in seed exchange based on mutual interdependence and trust. A government-imposed extension program must validate the role of local seed systems in developing a national seed industry

  6. The repeated evolution of large seeds on islands.

    Science.gov (United States)

    Kavanagh, Patrick H; Burns, Kevin C

    2014-07-07

    Several plant traits are known to evolve in predictable ways on islands. For example, herbaceous species often evolve to become woody and species frequently evolve larger leaves, regardless of growth form. However, our understanding of how seed sizes might evolve on islands lags far behind other plant traits. Here, we conduct the first test for macroevolutionary patterns of seed size on islands. We tested for differences in seed size between 40 island-mainland taxonomic pairings from four island groups surrounding New Zealand. Seed size data were collected in the field and then augmented by published seed descriptions to produce a more comprehensive dataset. Seed sizes of insular plants were consistently larger than mainland relatives, even after accounting for differences in growth form, dispersal mode and evolutionary history. Selection may favour seed size increases on islands to reduce dispersibility, as long-distance dispersal may result in propagule mortality at sea. Alternatively, larger seeds tend to generate larger seedlings, which are more likely to establish and outcompete neighbours. Our results indicate there is a general tendency for the evolution of large seeds on islands, but the mechanisms responsible for this evolutionary pathway have yet to be fully resolved. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  7. Wind dispersal of alien plant species into remnant natural vegetation from adjacent agricultural fields

    Directory of Open Access Journals (Sweden)

    Chika Egawa

    2017-07-01

    Full Text Available Knowledge regarding the seed dispersal of alien species is crucial to manage invasion risk in fragmented natural habitats. Focusing on wind dispersal, this study assessed the spatial and quantitative extents to which a remnant natural fen receives the seeds of alien species dispersed from adjacent hay meadows in Hokkaido, northern Japan. I established a total of 80 funnel seed traps in the fen at distances of 1, 2, 5, 10, 20, 30, 50, and 100 m from the meadows. The proportion of alien species in the seed rain at each distance was quantified, and the 99th-percentile dispersal distance from the meadows was estimated for each alien species by constructing dispersal kernels. Despite the presence of a marginal ditch and an elevational difference between the fen and the meadows, five alien species, including four grasses that do not have modified seed structures for wind dispersal, dispersed their seeds into the fen. These alien species accounted for up to 65.9% of the seed rain in terms of quantity. The 99th-percentile dispersal distances of the alien species ranged from 3.8 m to 309.3 m, and these distances were longer than the values predicted on the basis of their functional traits, such as terminal velocity. The results of this study demonstrated that numerous seeds of farmland-derived alien species were transported into the remnant vegetation via wind dispersal, and that simple predictions of dispersal distance based on functional traits could underestimate the potential area that alien species can reach. Continuous management both in farmland (to reduce seed escape and in remnant vegetation (to prevent the establishment of alien species is necessary to protect native vegetation from biological invasion in agricultural landscapes.

  8. Consecutive five-year analysis of paternal and maternal gene flow and contributions of gametic heterogeneities to overall genetic composition of dispersed seeds of Pinus densiflora (Pinaceae).

    Science.gov (United States)

    Iwaizumi, Masakazu G; Takahashi, Makoto; Isoda, Keiya; Austerlitz, Frédéric

    2013-09-01

    Genetic variability in monoecious woody plant populations results from the assemblage of individuals issued from asymmetrical male and female reproductive functions, produced during spatially and temporarily heterogeneous reproductive and dispersal events. Here we investigated the dispersal patterns and levels of genetic diversity and differentiation of both paternal and maternal gametes in a natural population of Pinus densiflora at the multiple-year scale as long as five consecutive years. • We analyzed the paternity and maternity for 1576 seeds and 454 candidate adult trees using nuclear DNA polymorphisms of diploid biparental embryos and haploid maternal megagametophytes at eight microsatellite loci. • Despite the low levels of genetic differentiation among gamete groups, a two-way AMOVA analysis showed that the parental origin (paternal vs. maternal gametes), the year of gamete production and their interaction had significant effects on the genetic composition of the seeds. While maternal gamete groups showed a significant FST value across the 5 years, this was not true for their paternal counterparts. Within the population, we found that the relative reproductive contributions of the paternal vs. the maternal parent differed among adult trees, the maternal contributions showing a larger year-to-year fluctuation. • The overall genetic variability of dispersed seeds appeared to result from two sources of heterogeneity: the difference between paternal and maternal patterns of reproduction and gamete dispersal and year-to-year heterogeneity of reproduction of adult trees, especially in their maternal reproduction.

  9. Frugivoria e dispersão de sementes pelo lagarto teiú Tupinambis merianae (Reptilia: Teiidae Frugivory and seed dispersal by the tegu lizard Tupinambis merianae Reptilia: Teiidae

    Directory of Open Access Journals (Sweden)

    Everaldo Rodrigo de Castro

    2004-01-01

    Full Text Available Os lagartos teiús possuem uma dieta generalista, podendo agir como importantes dispersores de sementes em florestas semidecíduas do sudeste do Brasil. Foram estudadas a frugivoria e a dispersão de sementes de lagartos teiús usando animais em cativeiro, através da oferta de frutos de uma floresta semidecídua. Frutos de trinta espécies vegetais foram oferecidos aos lagartos em cativeiro, com diâmetro variando de 0,81 a 10,0 cm. Não foram encontradas diferenças estatísticas na germinação entre as sementes que passaram pelo trato digestivo do lagarto e as controle de Eugenia uniflora (chi²= 0.69, P>0.50, Genipa americana (chi²= 6.4, P>0.975, Cereus peruvianus (chi²= 0.018, P>0.10, e Solanum viarum (chi²= 6.23, P>0.975. O tempo de retenção da semente no tubo digestivo do teiú variou de 22 a 23 h para Solanum lycocarpum e 43 a 44 h para Syagrus romanzoffiana. Nossos resultados indicam que o lagarto teiú tem potencial para agir como um importante dispersor de sementes nos trópicos.Tegu lizards have a generalist diet and may play an important role as seed dispersers in semideciduous forests in south-east Brazil. We studied the frugivory and seed dispersal of tegu lizards using captive animals and offering wild fruits from a semideciduous forest. Thirty fruit species were eaten by the lizards in captivity, ranging from 0.81 to 10.0 cm (fruit diameter. Even large fruit adapted to dispersal by large mammals were swallowed (ex. Syagrus oleracea. There were no statistical differences in seed germination between seeds that passed through the lizard gut and the control in Eugenia uniflora (chi2 = 0.69, P>0.50, Genipa americana (chi2 = 6.4, P>0.975, Cereus peruvianus (chi2 = 0.018, P>0.10, and Solanum viarum (chi2 = 6.23, P>0.975. Seed retention time in the tegu gut ranged from 2224 h (Solanum lycocarpum to 4344 h (for Syagrus romanzoffiana. Our results indicate that tegu lizards have a potential to be an important seed dispersers in the

  10. Between-site differences in the scale of dispersal and gene flow in red oak.

    Directory of Open Access Journals (Sweden)

    Emily V Moran

    Full Text Available Nut-bearing trees, including oaks (Quercus spp., are considered to be highly dispersal limited, leading to concerns about their ability to colonize new sites or migrate in response to climate change. However, estimating seed dispersal is challenging in species that are secondarily dispersed by animals, and differences in disperser abundance or behavior could lead to large spatio-temporal variation in dispersal ability. Parentage and dispersal analyses combining genetic and ecological data provide accurate estimates of current dispersal, while spatial genetic structure (SGS can shed light on past patterns of dispersal and establishment.In this study, we estimate seed and pollen dispersal and parentage for two mixed-species red oak populations using a hierarchical bayesian approach. We compare these results to those of a genetic ML parentage model. We also test whether observed patterns of SGS in three size cohorts are consistent with known site history and current dispersal patterns. We find that, while pollen dispersal is extensive at both sites, the scale of seed dispersal differs substantially. Parentage results differ between models due to additional data included in bayesian model and differing genotyping error assumptions, but both indicate between-site dispersal differences. Patterns of SGS in large adults, small adults, and seedlings are consistent with known site history (farmed vs. selectively harvested, and with long-term differences in seed dispersal. This difference is consistent with predator/disperser satiation due to higher acorn production at the low-dispersal site. While this site-to-site variation results in substantial differences in asymptotic spread rates, dispersal for both sites is substantially lower than required to track latitudinal temperature shifts.Animal-dispersed trees can exhibit considerable spatial variation in seed dispersal, although patterns may be surprisingly constant over time. However, even under

  11. Metatranscriptome Analysis of Fig Flowers Provides Insights into Potential Mechanisms for Mutualism Stability and Gall Induction.

    Directory of Open Access Journals (Sweden)

    Ellen O Martinson

    Full Text Available A striking property of the mutualism between figs and their pollinating wasps is that wasps consistently oviposit in the inner flowers of the fig syconium, which develop into galls that house developing larvae. Wasps typically do not use the outer ring of flowers, which develop into seeds. To better understand differences between gall and seed flowers, we used a metatranscriptomic approach to analyze eukaryotic gene expression within fig flowers at the time of oviposition choice and early gall development. Consistent with the unbeatable seed hypothesis, we found significant differences in gene expression between gall- and seed flowers in receptive syconia prior to oviposition. In particular, transcripts assigned to flavonoids and carbohydrate metabolism were significantly up-regulated in gall flowers relative to seed flowers. In response to oviposition, gall flowers significantly up-regulated the expression of chalcone synthase, which previously has been connected to gall formation in other plants. We propose several genes encoding proteins with signal peptides or associations with venom of other Hymenoptera as candidate genes for gall initiation or growth. This study simultaneously evaluates the gene expression profile of both mutualistic partners in a plant-insect mutualism and provides insight into a possible stability mechanism in the ancient fig-fig wasp association.

  12. Invasive acacias experience higher ant seed removal rates at the invasion edges

    Directory of Open Access Journals (Sweden)

    D. Montesinos

    2012-06-01

    Full Text Available Seed dispersal is a key process for the invasion of new areas by exotic species. Introduced plants often take advantage of native generalist dispersers. Australian acacias are primarily dispersed by ants in their native range and produce seeds bearing a protein and lipid rich reward for ant mutualists (elaiosome. Nevertheless, the role of myrmecochory in the expansion of Australian acacias in European invaded areas is still not clear. We selected one European population of Acacia dealbata and another of A. longifolia and offered elaiosome-bearing and elaiosome-removed seeds to local ant communities. For each species, seeds were offered both in high-density acacia stands and in low-density invasion edges. For both acacia species, seed removal was significantly higher at the low-density edges. For A. longifolia, manual elimination of elaiosomes reduced the chance of seed removal by 80% in the low-density edges, whereas it made no difference on the high-density stands. For A. dealbata, the absence of elaiosome reduced seed removal rate by 52%, independently of the acacia density. Our data suggests that invasive acacias have found effective ant seed dispersers in Europe and that the importance of such dispersers is higher at the invasion edges.

  13. Seed Dispersal, Microsites or Competition—What Drives Gap Regeneration in an Old-Growth Forest? An Application of Spatial Point Process Modelling

    Directory of Open Access Journals (Sweden)

    Georg Gratzer

    2018-04-01

    Full Text Available The spatial structure of trees is a template for forest dynamics and the outcome of a variety of processes in ecosystems. Identifying the contribution and magnitude of the different drivers is an age-old task in plant ecology. Recently, the modelling of a spatial point process was used to identify factors driving the spatial distribution of trees at stand scales. Processes driving the coexistence of trees, however, frequently unfold within gaps and questions on the role of resource heterogeneity within-gaps have become central issues in community ecology. We tested the applicability of a spatial point process modelling approach for quantifying the effects of seed dispersal, within gap light environment, microsite heterogeneity, and competition on the generation of within gap spatial structure of small tree seedlings in a temperate, old growth, mixed-species forest. By fitting a non-homogeneous Neyman–Scott point process model, we could disentangle the role of seed dispersal from niche partitioning for within gap tree establishment and did not detect seed densities as a factor explaining the clustering of small trees. We found only a very weak indication for partitioning of within gap light among the three species and detected a clear niche segregation of Picea abies (L. Karst. on nurse logs. The other two dominating species, Abies alba Mill. and Fagus sylvatica L., did not show signs of within gap segregation.

  14. Nectar bacteria, but not yeast, weaken a plant-pollinator mutualism.

    Science.gov (United States)

    Vannette, Rachel L; Gauthier, Marie-Pierre L; Fukami, Tadashi

    2013-02-07

    Mutualistic interactions are often subject to exploitation by species that are not directly involved in the mutualism. Understanding which organisms act as such 'third-party' species and how they do so is a major challenge in the current study of mutualistic interactions. Here, we show that even species that appear ecologically similar can have contrasting effects as third-party species. We experimentally compared the effects of nectar-inhabiting bacteria and yeasts on the strength of a mutualism between a hummingbird-pollinated shrub, Mimulus aurantiacus, and its pollinators. We found that the common bacterium Gluconobacter sp., but not the common yeast Metschnikowia reukaufii, reduced pollination success, seed set and nectar consumption by pollinators, thereby weakening the plant-pollinator mutualism. We also found that the bacteria reduced nectar pH and total sugar concentration more greatly than the yeasts did and that the bacteria decreased glucose concentration and increased fructose concentration whereas the yeasts affected neither. These distinct changes to nectar chemistry may underlie the microbes' contrasting effects on the mutualism. Our results suggest that it is necessary to understand the determinants of microbial species composition in nectar and their differential modification of floral rewards to explain the mutual benefits that plants and pollinators gain from each other.

  15. Nectar bacteria, but not yeast, weaken a plant–pollinator mutualism

    Science.gov (United States)

    Vannette, Rachel L.; Gauthier, Marie-Pierre L.; Fukami, Tadashi

    2013-01-01

    Mutualistic interactions are often subject to exploitation by species that are not directly involved in the mutualism. Understanding which organisms act as such ‘third-party’ species and how they do so is a major challenge in the current study of mutualistic interactions. Here, we show that even species that appear ecologically similar can have contrasting effects as third-party species. We experimentally compared the effects of nectar-inhabiting bacteria and yeasts on the strength of a mutualism between a hummingbird-pollinated shrub, Mimulus aurantiacus, and its pollinators. We found that the common bacterium Gluconobacter sp., but not the common yeast Metschnikowia reukaufii, reduced pollination success, seed set and nectar consumption by pollinators, thereby weakening the plant–pollinator mutualism. We also found that the bacteria reduced nectar pH and total sugar concentration more greatly than the yeasts did and that the bacteria decreased glucose concentration and increased fructose concentration whereas the yeasts affected neither. These distinct changes to nectar chemistry may underlie the microbes' contrasting effects on the mutualism. Our results suggest that it is necessary to understand the determinants of microbial species composition in nectar and their differential modification of floral rewards to explain the mutual benefits that plants and pollinators gain from each other. PMID:23222453

  16. Seed dormancy and germination : light and nitrate

    NARCIS (Netherlands)

    Hilhorst, H.W.M.

    1990-01-01

    One of the most important aspects of the life cycle of seed plants is the formation and development of seeds on the motherplant and the subsequent dispersal. An equally important element of the survival strategy is the ability of seeds to prevent germination in unfavorable

  17. Dispersal limitation of Tillandsia species correlates with rain and host structure in a central Mexican tropical dry forest.

    Science.gov (United States)

    Victoriano-Romero, Elizabeth; Valencia-Díaz, Susana; Toledo-Hernández, Víctor Hugo; Flores-Palacios, Alejandro

    2017-01-01

    Seed dispersal permits the colonization of favorable habitats and generation of new populations, facilitating escape from habitats that are in decline. There is little experimental evidence of the factors that limit epiphyte dispersion towards their hosts. In a tropical dry forest in central Mexico, we monitored the phenology of dispersion of epiphyte species of the genus Tillandsia; we tested experimentally whether precipitation could cause failures in seed dispersal and whether seed capture differs among vertical strata and between host species with high (Bursera copallifera) and low (Conzattia multiflora) epiphyte loads. With the exception of one species that presents late dispersion and low abundance, all of the species disperse prior to the onset of the rainy season. However, early rains immobilize the seeds, affecting up to 24% of the fruits in species with late dispersion. We observed that Tillandsia seeds reach both Bursera and Conzattia hosts, but found that adherence to the host is 4-5 times higher in Bursera. Furthermore, seeds liberated from Bursera travel shorter distances and up to half may remain within the same crown, while the highest seed capture takes place in the upper strata of the trees. We conclude that dispersion of Tillandsia seeds is limited by early rains and by the capture of seeds within the trees where populations concentrate. This pattern of capture also helps to explain the high concentrations of epiphytes in certain hosts, while trees with few epiphytes can be simultaneously considered deficient receivers and efficient exporters of seeds.

  18. Effects of liana load, tree diameter and distances between conspecifics on seed production in tropical timber trees

    DEFF Research Database (Denmark)

    Nabe-Nielsen, Jacob; Kollmann, Johannes Christian; Peña-Claros, Marielos

    2009-01-01

    Seed production in tropical timber trees is limited by abiotic resources, pollination and pre-dispersal seed predation. Resource availability is influenced by the number of competing trees and by lianas that often reach high densities in disturbed parts of tropical forests. The distance between...... conspecific trees affects pollination efficiency and seed predation intensity, and may therefore indirectly affect the long-term sustainability of selective logging. Here we investigate how reproductive status and the number of seeds dispersed per tree are affected by liana load, distance to the nearest...... and positively with tree diameter. In C. ianeirensis the most liana-infested trees dispersed fewer seeds. In T. oblonga the intensity of pre-dispersal seed predation decreased with distance to the nearest conspecifics. There was no evidence that seed viability or seed production decreased with distance...

  19. Mutual diffusion of sodium hyaluranate in aqueous solutions

    International Nuclear Information System (INIS)

    Veríssimo, Luís M.P.; Valada, Teresa I.C.; Sobral, Abilio J.F.N.; Azevedo, Eduarda E.F.G.; Azevedo, Maria L.G.; Ribeiro, Ana C.F.

    2014-01-01

    Highlights: • Binary diffusion coefficients for the systems containing sodium hyaluronate. • Influence of the aggregation on diffusion of the sodium hyaluronate in the aqueous media. • Estimation of the thermodynamic and mobility factors from mutual diffusion. -- Abstract: The Taylor dispersion technique has been used for measuring mutual diffusion coefficients of sodium hyaluronate in aqueous solutions at T = 298.15 K, and concentrations ranging from (0.00 to 0.50) g · dm −3 . The results are interpreted on the basis of Nernst, and Onsager and Fuoss theoretical equations. From the diffusion coefficient at infinitesimal concentration, the limiting ionic conductivity and the tracer diffusion coefficient of hyaluronate ion were estimated. These studies have been complemented by molecular mechanics calculations

  20. Seed predators exert selection on the subindividual variation of seed size.

    Science.gov (United States)

    Sobral, M; Guitián, J; Guitián, P; Larrinaga, A R

    2014-07-01

    Subindividual variation among repeated organs in plants constitutes an overlooked level of variation in phenotypic selection studies, despite being a major component of phenotypic variation. Animals that interact with plants could be selective agents on subindividual variation. This study examines selective pressures exerted during post-dispersal seed predation and germination on the subindividual variation of seed size in hawthorn (Crataegus monogyna). With a seed offering experiment and a germination test, we estimated phenotypic selection differentials for average and subindividual variation of seed size due to seed predation and germination. Seed size affects germination, growth rate and the probability of an individual seed of escaping predation. Longer seeds showed higher germination rates, but this did not result in significant selection on phenotypes of the maternal trees. On the other hand, seed predators avoided wider seeds, and by doing so exerted phenotypic selection on adult average and subindividual variation of seed size. The detected selection on subindividual variation suggests that the levels of phenotypic variation within individual plants may be, at least partly, the adaptive consequence of animal-mediated selection. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.

  1. Dispersal limitation of Tillandsia species correlates with rain and host structure in a central Mexican tropical dry forest.

    Directory of Open Access Journals (Sweden)

    Elizabeth Victoriano-Romero

    Full Text Available Seed dispersal permits the colonization of favorable habitats and generation of new populations, facilitating escape from habitats that are in decline. There is little experimental evidence of the factors that limit epiphyte dispersion towards their hosts. In a tropical dry forest in central Mexico, we monitored the phenology of dispersion of epiphyte species of the genus Tillandsia; we tested experimentally whether precipitation could cause failures in seed dispersal and whether seed capture differs among vertical strata and between host species with high (Bursera copallifera and low (Conzattia multiflora epiphyte loads. With the exception of one species that presents late dispersion and low abundance, all of the species disperse prior to the onset of the rainy season. However, early rains immobilize the seeds, affecting up to 24% of the fruits in species with late dispersion. We observed that Tillandsia seeds reach both Bursera and Conzattia hosts, but found that adherence to the host is 4-5 times higher in Bursera. Furthermore, seeds liberated from Bursera travel shorter distances and up to half may remain within the same crown, while the highest seed capture takes place in the upper strata of the trees. We conclude that dispersion of Tillandsia seeds is limited by early rains and by the capture of seeds within the trees where populations concentrate. This pattern of capture also helps to explain the high concentrations of epiphytes in certain hosts, while trees with few epiphytes can be simultaneously considered deficient receivers and efficient exporters of seeds.

  2. Dormancy cycling in seeds: mechanisms and regulation

    NARCIS (Netherlands)

    Claessens, S.M.C.

    2012-01-01

    The life cycle of most plants starts, and ends, at the seed stage. In most species mature seeds are shed and dispersed on the ground. At this stage of its life cycle the seed may be dormant and will, by definition, not germinate under favourable conditions (Bewley, 1997).

    Seasonal

  3. DETECTION OF POLLEN FLOW IN THE SEEDLING SEED ORCHARD OF Acacia mangium USING DNA MARKER

    Directory of Open Access Journals (Sweden)

    Vivi Yuskianti

    2013-06-01

    Full Text Available Pollen pattern dispersal in seedling seed orchard (SSO is an essential part of a tree-improvement program. Two SSOs of Acacia mangium in South Kalimantan and South Sumatra that represent similar resources in different environments were used in this study.  Genotypes of all trees and seeds from a subset of 10 mother trees in each orchard were determined for 12 microsatellite loci, and parentage analysis was carried out. The results shows that the pollen dispersal pattern in both SSOs decrease with distance from mother tree. Patterns of pollen dispersal, dispersal distance and cumulative frequency of pollen dispersal distance were similar in both SSOs. Random pollen dispersal were found in both SSOs. About 80% of all crosses were found within a 40-m distance range with the most frequent pollination distance between mother tree and male male parents was 0-10 m. No self-pollinated seed was detected. Application of all these aspects found in this study such as random pollen dispersal and the effective pollen dispersal distance can be useful for establishing seedling seed orchard, clonal seed orchard and in other tree improvement activities of A. mangium.

  4. Waterfowl endozoochory: An overlooked long-distance dispersal mode for Cuscuta (dodder).

    Science.gov (United States)

    Costea, Mihai; Stefanović, Saša; García, Miguel A; De La Cruz, Susan; Casazza, Michael L; Green, Andy J

    2016-05-01

    Dispersal of parasitic Cuscuta species (dodders) worldwide has been assumed to be largely anthropomorphic because their seeds do not match any previously known dispersal syndrome and no natural dispersal vectors have been reliably documented. However, the genus has a subcosmopolitan distribution and recent phylogeographic results have indicated that at least18 historical cases of long-distance dispersal (LDD) have occurred during its evolution. The objective of this study is to report the first LDD biological vector for Cuscuta seeds. Twelve northern pintails (Anas acuta) were collected from Suisun Marsh, California and the contents of their lowest part of the large intestine (rectum) were extracted and analyzed. Seed identification was done both morphologically and using a molecular approach. Extracted seeds were tested for germination and compared to seeds not subjected to gut passage to determine the extent of structural changes caused to the seed coat by passing through the digestive tract. Four hundred and twenty dodder seeds were found in the rectum of four northern pintails. From these, 411 seeds were identified as Cuscuta campestris and nine as most likely C. pacifica. The germination rate of C. campestris seeds after gut passage was 55%. Structural changes caused by the gut passage in both species were similar to those caused by an acid scarification. Endozoochory by waterbirds may explain the historical LDD cases in the evolution of Cuscuta. This also suggests that current border quarantine measures may be insufficient to stopping spreading of dodder pests along migratory flyways. © 2016 Botanical Society of America.

  5. Influence of seed density and aggregation on post-dispersal weed seed predation in cereal fields

    NARCIS (Netherlands)

    Marino, P.C.; Westerman, P.R.; Pinkert, C.; Werf, van der W.

    2005-01-01

    The importance of density dependence, aggregation and background density of seeds on intensity of seed predation in cereal fields were examined in central Netherlands. Four sequential 1-week trials were conducted from 9 July to 8 August 2001 and lamb's quarters (Chenopodium album) was used as the

  6. Preparation and thermodynamic stability of micron-sized, monodisperse composite polymer particles of disc-like shapes by seeded dispersion polymerization.

    Science.gov (United States)

    Fujibayashi, Teruhisa; Okubo, Masayoshi

    2007-07-17

    Micron-sized, monodisperse composite polymer particles having "disc-like" and "polyhedral" shapes were prepared by seeded dispersion polymerization of 2-ethylhexylmethacrylate (EHMA) with 2.67-mum-sized polystyrene (PS) seed particles in methanol/water media in the presence of droplets of various saturated hydrocarbons and evaporation of the hydrocarbon after the polymerization. Such nonspherical shapes were based on the volume reduction due to the evaporation. The primary factors influencing the particle shape seemed to be the absorption rate of the hydrocarbon into the resulting PS/poly(EHMA)/hydrocarbon composite particles during the polymerization, which affected the viscosities and the volumes of the PS and poly(EHMA) phases. It was found that the morphological development during the polymerization was retarded at "hamburger-like" morphology, which is a precursor of the disc-like particle, although this morphology is a thermodynamically metastable state.

  7. Mutualism Disruption Threatens Global Plant Biodiversity: A Systematic Review.

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    Clare E Aslan

    Full Text Available As global environmental change accelerates, biodiversity losses can disrupt interspecific interactions. Extinctions of mutualist partners can create "widow" species, which may face reduced ecological fitness. Hypothetically, such mutualism disruptions could have cascading effects on biodiversity by causing additional species coextinctions. However, the scope of this problem - the magnitude of biodiversity that may lose mutualist partners and the consequences of these losses - remains unknown.We conducted a systematic review and synthesis of data from a broad range of sources to estimate the threat posed by vertebrate extinctions to the global biodiversity of vertebrate-dispersed and -pollinated plants. Though enormous research gaps persist, our analysis identified Africa, Asia, the Caribbean, and global oceanic islands as geographic regions at particular risk of disruption of these mutualisms; within these regions, percentages of plant species likely affected range from 2.1-4.5%. Widowed plants are likely to experience reproductive declines of 40-58%, potentially threatening their persistence in the context of other global change stresses.Our systematic approach demonstrates that thousands of species may be impacted by disruption in one class of mutualisms, but extinctions will likely disrupt other mutualisms, as well. Although uncertainty is high, there is evidence that mutualism disruption directly threatens significant biodiversity in some geographic regions. Conservation measures with explicit focus on mutualistic functions could be necessary to bolster populations of widowed species and maintain ecosystem functions.

  8. Mutualism and impacts of global change: response of an important and neglected component of the biodiversity

    International Nuclear Information System (INIS)

    Hossaert-Mckey, M.

    2007-01-01

    We are studying the impact of global change on two obligate species-specific insect-plant mutualisms. Our approach combines correlative methods (examining spatial patterns of genetic diversity in populations of pairs of mutualists, to examine their responses to past climate change) and experiments (studying responses of plant partners to CO 2 fertilization). Mutualisms function because the partners have contrasting and complementary biological traits, so that a service implying only a low cost to one partner may confer a great benefit to the other. Because they can lead mutualist partners to respond differently to rapid ecological change, the biological differences that are fundamental to mutualisms may also make them vulnerable. Imbalances thereby introduced can disrupt the functioning of the mutualism. By comparing two strongly contrasting systems-fig/wasp pollination mutualisms and ant-plant protection mutualisms-we aim to characterize the diversity of responses of mutualisms to global change. By identifying points in common, we also aim to propose robust generalizations about the response to global change of obligate, specific mutualisms, an important and neglected component of tropical biodiversity. Our results show that the two mutualisms studied differ greatly in their response to Pleistocene and Holocene climatic fluctuations. Fig/wasp systems show little spatial genetic differentiation, indicating that the great dispersal capacities of both figs and their pollinating wasps resulted in maintenance of high effective population sizes throughout cycles of climatic and vegetation change. In contrast, limited dispersal capacity of both ant and plant partners has resulted in greater impact of climatic fluctuations on ant/plant protection mutualisms: species-distribution patterns suggest restriction of the system to refugia, and strong spatial genetic structure indicates widespread bottlenecks during fragmentation and expansion. Alternate contraction and expansion

  9. Investment in seed physical defence is associated with species' light requirement for regeneration and seed persistence: evidence from Macaranga species in Borneo

    Science.gov (United States)

    The life stage from seed dispersal to seedling emergence is often critical in determining the regeneration success of plants. During this period seeds must survive an array of seed predators and pathogens and germinate under conditions favorable for seedling establishment. To maximise recruitment s...

  10. Intra-specific downsizing of frugivores affects seed germination of fleshy-fruited plant species

    Science.gov (United States)

    Pérez-Méndez, Néstor; Rodríguez, Airam; Nogales, Manuel

    2018-01-01

    The loss of largest-bodied individuals within species of frugivorous animals is one of the major consequences of defaunation. The gradual disappearance of large-bodied frugivores is expected to entail a parallel deterioration in seed dispersal functionality if the remaining smaller-sized individuals are not so effective as seed dispersers. While the multiple impacts of the extinction of large bodied species have been relatively well studied, the impact of intraspecific downsizing (i.e. the extinction of large individuals within species) on seed dispersal has rarely been evaluated. Here we experimentally assessed the impact of body-size reduction in the frugivorous lizard Gallotia galloti (Lacertidae), an endemic species of the Canary Islands, on the seed germination patterns of two fleshy-fruited plant species (Rubia fruticosa and Withania aristata). Seed germination curves and the proportions of germinated seeds were compared for both plant species after being defecated by large-sized individuals and small-sized individuals. The data show that seeds of W. aristata defecated by larger-sized lizards germinated faster and in a higher percentage than those defecated by small-sized lizards, while no differences were found for R. fruticosa seeds. Our results suggest that disappearance of the largest individuals of frugivorous species may impair recruitment of some plant species by worsening seed germination. They also warn us of a potential cryptic loss of seed dispersal functionality on defaunated ecosystems, even when frugivorous species remain abundant.

  11. Burial increases seed longevity of two Artemisia tridentata (Asteraceae) subspecies

    Science.gov (United States)

    Wijayratne, Upekala C.; Pyke, David A.

    2012-01-01

    Premise of the study: Seed longevity and persistence in soil seed banks may be especially important for population persistence in ecosystems where opportunities for seedling establishment and disturbance are unpredictable. The fire regime, an important driver of population dynamics in sagebrush steppe ecosystems, has been altered by exotic annual grass invasion. Soil seed banks may play an active role in postfire recovery of the foundation shrub Artemisia tridentata, yet conditions under which seeds persist are largely unknown. Methods: We investigated seed longevity of two Artemisia tridentata subspecies in situ by retrieving seed bags that were placed at varying depths over a 2 yr period. We also sampled naturally dispersed seeds in litter and soil immediately after seed dispersal and before flowering in subsequent seasons to estimate seed persistence. Key results: After 24 mo, seeds buried at least 3 cm below the soil surface retained 30–40% viability whereas viability of seeds on the surface and under litter declined to 0 and Artemisia tridentata has the potential to form a short-term soil seed bank that persists longer than has been commonly assumed, and that burial is necessary for seed longevity. Use of seeding techniques that promote burial of some seeds to aid in formation of a soil seed bank may increase restoration potential.

  12. Reduced hornbill abundance associated with low seed arrival and altered recruitment in a hunted and logged tropical forest.

    Directory of Open Access Journals (Sweden)

    Rohit Naniwadekar

    Full Text Available Logging and hunting are two key direct threats to the survival of wildlife in the tropics, and also disrupt important ecosystem processes. We investigated the impacts of these two factors on the different stages of the seed dispersal cycle, including abundance of plants and their dispersers and dispersal of seeds and recruitment, in a tropical forest in north-east India. We focused on hornbills, which are important seed dispersers in these forests, and their food tree species. We compared abundances of hornbill food tree species in a site with high logging and hunting pressures (heavily disturbed with a site that had no logging and relatively low levels of hunting (less disturbed to understand logging impacts on hornbill food tree abundance. We compared hornbill abundances across these two sites. We, then, compared the scatter-dispersed seed arrival of five large-seeded tree species and the recruitment of four of those species. Abundances of hornbill food trees that are preferentially targeted by logging were two times higher in the less disturbed site as compared to the heavily disturbed site while that of hornbills was 22 times higher. The arrival of scatter-dispersed seeds was seven times higher in the less disturbed site. Abundances of recruits of two tree species were significantly higher in the less disturbed site. For another species, abundances of younger recruits were significantly lower while that of older recruits were higher in the heavily disturbed site. Our findings suggest that logging reduces food plant abundance for an important frugivore-seed disperser group, while hunting diminishes disperser abundances, with an associated reduction in seed arrival and altered recruitment of animal-dispersed tree species in the disturbed site. Based on our results, we present a conceptual model depicting the relationships and pathways between vertebrate-dispersed trees, their dispersers, and the impacts of hunting and logging on these pathways.

  13. Reduced hornbill abundance associated with low seed arrival and altered recruitment in a hunted and logged tropical forest.

    Science.gov (United States)

    Naniwadekar, Rohit; Shukla, Ushma; Isvaran, Kavita; Datta, Aparajita

    2015-01-01

    Logging and hunting are two key direct threats to the survival of wildlife in the tropics, and also disrupt important ecosystem processes. We investigated the impacts of these two factors on the different stages of the seed dispersal cycle, including abundance of plants and their dispersers and dispersal of seeds and recruitment, in a tropical forest in north-east India. We focused on hornbills, which are important seed dispersers in these forests, and their food tree species. We compared abundances of hornbill food tree species in a site with high logging and hunting pressures (heavily disturbed) with a site that had no logging and relatively low levels of hunting (less disturbed) to understand logging impacts on hornbill food tree abundance. We compared hornbill abundances across these two sites. We, then, compared the scatter-dispersed seed arrival of five large-seeded tree species and the recruitment of four of those species. Abundances of hornbill food trees that are preferentially targeted by logging were two times higher in the less disturbed site as compared to the heavily disturbed site while that of hornbills was 22 times higher. The arrival of scatter-dispersed seeds was seven times higher in the less disturbed site. Abundances of recruits of two tree species were significantly higher in the less disturbed site. For another species, abundances of younger recruits were significantly lower while that of older recruits were higher in the heavily disturbed site. Our findings suggest that logging reduces food plant abundance for an important frugivore-seed disperser group, while hunting diminishes disperser abundances, with an associated reduction in seed arrival and altered recruitment of animal-dispersed tree species in the disturbed site. Based on our results, we present a conceptual model depicting the relationships and pathways between vertebrate-dispersed trees, their dispersers, and the impacts of hunting and logging on these pathways.

  14. Reduced Hornbill Abundance Associated with Low Seed Arrival and Altered Recruitment in a Hunted and Logged Tropical Forest

    Science.gov (United States)

    Naniwadekar, Rohit; Shukla, Ushma; Isvaran, Kavita; Datta, Aparajita

    2015-01-01

    Logging and hunting are two key direct threats to the survival of wildlife in the tropics, and also disrupt important ecosystem processes. We investigated the impacts of these two factors on the different stages of the seed dispersal cycle, including abundance of plants and their dispersers and dispersal of seeds and recruitment, in a tropical forest in north-east India. We focused on hornbills, which are important seed dispersers in these forests, and their food tree species. We compared abundances of hornbill food tree species in a site with high logging and hunting pressures (heavily disturbed) with a site that had no logging and relatively low levels of hunting (less disturbed) to understand logging impacts on hornbill food tree abundance. We compared hornbill abundances across these two sites. We, then, compared the scatter-dispersed seed arrival of five large-seeded tree species and the recruitment of four of those species. Abundances of hornbill food trees that are preferentially targeted by logging were two times higher in the less disturbed site as compared to the heavily disturbed site while that of hornbills was 22 times higher. The arrival of scatter-dispersed seeds was seven times higher in the less disturbed site. Abundances of recruits of two tree species were significantly higher in the less disturbed site. For another species, abundances of younger recruits were significantly lower while that of older recruits were higher in the heavily disturbed site. Our findings suggest that logging reduces food plant abundance for an important frugivore-seed disperser group, while hunting diminishes disperser abundances, with an associated reduction in seed arrival and altered recruitment of animal-dispersed tree species in the disturbed site. Based on our results, we present a conceptual model depicting the relationships and pathways between vertebrate-dispersed trees, their dispersers, and the impacts of hunting and logging on these pathways. PMID:25781944

  15. 26 CFR 1.831-3 - Tax on insurance companies (other than life or mutual), mutual marine insurance companies, mutual...

    Science.gov (United States)

    2010-04-01

    ... mutual), mutual marine insurance companies, mutual fire insurance companies issuing perpetual policies, and mutual fire or flood insurance companies operating on the basis of premium deposits; taxable years... fire insurance companies issuing perpetual policies, and mutual fire or flood insurance companies...

  16. Investigating Seed Longevity of Big Sagebrush (Artemisia tridentata)

    Science.gov (United States)

    Wijayratne, Upekala C.; Pyke, David A.

    2009-01-01

    The Intermountain West is dominated by big sagebrush communities (Artemisia tridentata subspecies) that provide habitat and forage for wildlife, prevent erosion, and are economically important to recreation and livestock industries. The two most prominent subspecies of big sagebrush in this region are Wyoming big sagebrush (A. t. ssp. wyomingensis) and mountain big sagebrush (A. t. ssp. vaseyana). Increased understanding of seed bank dynamics will assist with sustainable management and persistence of sagebrush communities. For example, mountain big sagebrush may be subjected to shorter fire return intervals and prescribed fire is a tool used often to rejuvenate stands and reduce tree (Juniperus sp. or Pinus sp.) encroachment into these communities. A persistent seed bank for mountain big sagebrush would be advantageous under these circumstances. Laboratory germination trials indicate that seed dormancy in big sagebrush may be habitat-specific, with collections from colder sites being more dormant. Our objective was to investigate seed longevity of both subspecies by evaluating viability of seeds in the field with a seed retrieval experiment and sampling for seeds in situ. We chose six study sites for each subspecies. These sites were dispersed across eastern Oregon, southern Idaho, northwestern Utah, and eastern Nevada. Ninety-six polyester mesh bags, each containing 100 seeds of a subspecies, were placed at each site during November 2006. Seed bags were placed in three locations: (1) at the soil surface above litter, (2) on the soil surface beneath litter, and (3) 3 cm below the soil surface to determine whether dormancy is affected by continued darkness or environmental conditions. Subsets of seeds were examined in April and November in both 2007 and 2008 to determine seed viability dynamics. Seed bank samples were taken at each site, separated into litter and soil fractions, and assessed for number of germinable seeds in a greenhouse. Community composition data

  17. Population size, center-periphery, and seed dispersers' effects on the genetic diversity and population structure of the Mediterranean relict shrub Cneorum tricoccon.

    Science.gov (United States)

    Lázaro-Nogal, Ana; Matesanz, Silvia; García-Fernández, Alfredo; Traveset, Anna; Valladares, Fernando

    2017-09-01

    The effect of population size on population genetic diversity and structure has rarely been studied jointly with other factors such as the position of a population within the species' distribution range or the presence of mutualistic partners influencing dispersal. Understanding these determining factors for genetic variation is critical for conservation of relict plants that are generally suffering from genetic deterioration. Working with 16 populations of the vulnerable relict shrub Cneorum tricoccon throughout the majority of its western Mediterranean distribution range, and using nine polymorphic microsatellite markers, we examined the effects of periphery (peripheral vs. central), population size (large vs. small), and seed disperser (introduced carnivores vs. endemic lizards) on the genetic diversity and population structure of the species. Contrasting genetic variation ( H E : 0.04-0.476) was found across populations. Peripheral populations showed lower genetic diversity, but this was dependent on population size. Large peripheral populations showed high levels of genetic diversity, whereas small central populations were less diverse. Significant isolation by distance was detected, indicating that the effect of long-distance gene flow is limited relative to that of genetic drift, probably due to high selfing rates ( F IS  = 0.155-0.887), restricted pollen flow, and ineffective seed dispersal. Bayesian clustering also supported the strong population differentiation and highly fragmented structure. Contrary to expectations, the type of disperser showed no significant effect on either population genetic diversity or structure. Our results challenge the idea of an effect of periphery per se that can be mainly explained by population size, drawing attention to the need of integrative approaches considering different determinants of genetic variation. Furthermore, the very low genetic diversity observed in several small populations and the strong among

  18. Mutualism Persistence and Abandonment during the Evolution of the Mycorrhizal Symbiosis.

    Science.gov (United States)

    Maherali, Hafiz; Oberle, Brad; Stevens, Peter F; Cornwell, William K; McGlinn, Daniel J

    2016-11-01

    Mutualistic symbioses with mycorrhizal fungi are widespread in plants. The majority of plant species associate with arbuscular mycorrhizal (AM) fungi. By contrast, the minority associate with ectomycorrhizal (EM) fungi, have abandoned the symbiosis and are nonmycorrhizal (NM), or engage in an intermediate, weakly AM symbiosis (AMNM). To understand the processes that maintain the mycorrhizal symbiosis or cause its loss, we reconstructed its evolution using a ∼3,000-species seed plant phylogeny integrated with mycorrhizal state information. Reconstruction indicated that the common ancestor of seed plants most likely associated with AM fungi and that the EM, NM, and AMNM states descended from the AM state. Direct transitions from the AM state to the EM and NM states were infrequent and generally irreversible, implying that natural selection or genetic constraint could promote stasis once a particular state evolved. However, the evolution of the NM state was more frequent via an indirect pathway through the AMNM state, suggesting that weakening of the AM symbiosis is a necessary precursor to mutualism abandonment. Nevertheless, reversions from the AMNM state back to the AM state were an order of magnitude more likely than transitions to the NM state, suggesting that natural selection favors the AM symbiosis over mutualism abandonment.

  19. Viability of small seeds found in feces of the Central American tapir on Barro Colorado Island, Panama.

    Science.gov (United States)

    Capece, Paula I; Aliaga-Rossel, Enzo; Jansen, Patrick A

    2013-03-01

    Tapirs are known as effective dispersers of large-seeded tree species, but their role in dispersing small-seeded plant species has yet to be established. Tapir feces have been reported to contain large numbers of small seeds, but whether these are viable has rarely been evaluated. We determined the abundance and viability of small seeds in feces of Central American tapir (Tapirus bairdii) on Barro Colorado Island, Panama. A total of 72 fecal samples were collected opportunistically from 4 tapir latrine sites. Seeds were manually extracted from feces and classified by size. Seed viability was estimated by opening each seed and examining for the presence of at least 1 intact firm white endosperm. In total, we obtained 8166 seeds of at least 16 plant species. Small-seeded species dominated, with 96% of all seeds found measuring tapirs potentially serve as effective dispersers of a wide range of small-seeded plant species. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

  20. Potential role of frugivorous birds (Passeriformes on seed dispersal of six plant species in a restinga habitat, southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Verônica Souza da Mota Gomes

    2008-03-01

    Full Text Available Restingas are considered stressful habitats associated with the Brazilian Atlantic forest, and their ecological interactions are poorly known. The goal of the present study was to determine the potential role of frugivorous birds as seed dispersers in a restinga habitat. Data were collected in Parque Nacional da Restinga de Jurubatiba, southeastern Brazil, where the main physiognomy (Open Clusia Formation is characterized by the presence of patches of vegetation covering 20 to 48 % of the sandy soil and reaching a height of 5 m. Birds were captured with mist nets (12 x 2.5 m; 36 mm mesh; 1 680 net-hrs and had their fecal and regurgitate samples inspected for seeds. Six plant species found in these bird samples were studied. The germination of seeds obtained from plants was compared to those from the birds. Both groups of seeds were set on Petri dishes at room temperature and washed when infected with fungi. In general, there was no effect on germination rate, and the effect on germination speed was negative. Germination of seeds from Pilosocereus arrabidae treated by the birds seemed to be influenced by storage of defecated seeds, while few Miconia cinnamomifolia seeds both from plants and from birds germinated. Ocotea notata presented a great variation in time to the onset of germination, perhaps an advantage against dissecation. Aechmea nudicaulis, Clusia hilariana and Erythroxylum subsessile probably take advantage of the arrival to favorable microhabitats, not by the gut effect on the seeds. All plant species studied are numerically important for the community and some of them are main actors in the succession of vegetation patches. Among the birds, Mimus gilvus is an important resident species, endemic to restingas in Brazil, while Turdus amaurochalinus is a visitor and may be important for plants that fructify during its passage by the study site. Although the effect of pulp removal was only tested for one species (Achmea nudicaulis in the

  1. Seed size and provenance mediate the joint effects of disturbance and seed predation on community assembly

    Science.gov (United States)

    John L. Maron; Dean E. Pearson; Teal Potter; Yvette K. Ortega

    2012-01-01

    Local plant community assembly is influenced by a series of filters that affect the recruitment and establishment of species. These filters include regional factors that limit seeds of any given species from reaching a local site as well as local interactions such as post-dispersal seed predation and disturbance, which dictate what species actually establish. How these...

  2. Colonization of abandoned land by Juniperus thurifera is mediated by the interaction of a diverse dispersal assemblage and environmental heterogeneity.

    Science.gov (United States)

    Escribano-Avila, Gema; Sanz-Pérez, Virginia; Pías, Beatriz; Virgós, Emilio; Escudero, Adrián; Valladares, Fernando

    2012-01-01

    Land abandonment is one of the most powerful global change drivers in developed countries where recent rural exodus has been the norm. Abandonment of traditional land use practices has permitted the colonization of these areas by shrub and tree species. For fleshy fruited species the colonization of new areas is determined by the dispersal assemblage composition and abundance. In this study we showed how the relative contribution to the dispersal process by each animal species is modulated by the environmental heterogeneity and ecosystem structure. This complex interaction caused differential patterns on the seed dispersal in both, landscape patches in which the process of colonization is acting nowadays and mature woodlands of Juniperus thurifera, a relict tree distributed in the western Mediterranean Basin. Thrushes (Turdus spp) and carnivores (red fox and stone marten) dispersed a high amount of seeds while rabbits and sheeps only a tiny fraction. Thrushes dispersed a significant amount of seeds in new colonization areas, however they were limited by the presence of high perches with big crop size. While carnivores dispersed seeds to all studied habitats, even in those patches where no trees of J. thurifera were present, turning out to be critical for primary colonization. The presence of Pinus and Quercus was related to a reduced consumption of J. thurifera seeds while the presence of fleshy fruited shrubs was related with higher content of J. thurifera seeds in dispersers' faeces. Therefore environmental heterogeneity and ecosystem structure had a great influence on dispersers feeding behaviour, and should be considered in order to accurately describe the role of seed dispersal in ecological process, such as regeneration and colonization. J. thurifera expansion is not seed limited thanks to its diverse dispersal community, hence the conservation of all dispersers in an ecosystem enhance ecosystems services and resilience.

  3. Colonization of abandoned land by Juniperus thurifera is mediated by the interaction of a diverse dispersal assemblage and environmental heterogeneity.

    Directory of Open Access Journals (Sweden)

    Gema Escribano-Avila

    Full Text Available Land abandonment is one of the most powerful global change drivers in developed countries where recent rural exodus has been the norm. Abandonment of traditional land use practices has permitted the colonization of these areas by shrub and tree species. For fleshy fruited species the colonization of new areas is determined by the dispersal assemblage composition and abundance. In this study we showed how the relative contribution to the dispersal process by each animal species is modulated by the environmental heterogeneity and ecosystem structure. This complex interaction caused differential patterns on the seed dispersal in both, landscape patches in which the process of colonization is acting nowadays and mature woodlands of Juniperus thurifera, a relict tree distributed in the western Mediterranean Basin. Thrushes (Turdus spp and carnivores (red fox and stone marten dispersed a high amount of seeds while rabbits and sheeps only a tiny fraction. Thrushes dispersed a significant amount of seeds in new colonization areas, however they were limited by the presence of high perches with big crop size. While carnivores dispersed seeds to all studied habitats, even in those patches where no trees of J. thurifera were present, turning out to be critical for primary colonization. The presence of Pinus and Quercus was related to a reduced consumption of J. thurifera seeds while the presence of fleshy fruited shrubs was related with higher content of J. thurifera seeds in dispersers' faeces. Therefore environmental heterogeneity and ecosystem structure had a great influence on dispersers feeding behaviour, and should be considered in order to accurately describe the role of seed dispersal in ecological process, such as regeneration and colonization. J. thurifera expansion is not seed limited thanks to its diverse dispersal community, hence the conservation of all dispersers in an ecosystem enhance ecosystems services and resilience.

  4. Overseas seed dispersal by migratory birds

    NARCIS (Netherlands)

    Viana, D.S.; Gangoso, L.; Bouten, W.; Figuerola, J.

    2016-01-01

    Long-distance dispersal (LDD) promotes the colonization of isolated and remote habitats, and thus it has been proposed as a mechanism for explaining the distributions of many species. Birds are key LDD vectors for many sessile organisms such as plants, yet LDD beyond local and regional scales has

  5. Phenology, fruit production and seed dispersal of Astrocaryum jauari (Arecaceae in Amazonian black water floodplains

    Directory of Open Access Journals (Sweden)

    F. Piedade Maria Teresa

    2006-12-01

    Full Text Available Astrocaryum jauari Mart. (Arecaceae is one of the commonest palm species occurring in nutritionally poor Amazonian black water floodplains. It is an emergent or subcanopy tree that grows on river banks and slands, with a wide distribution along the entire flooding gradient, tolerating flood durations between 30 and 340 days. The species is important for fish nutrition in the floodplains, and is also used for hearts of palm. In the present study, the auto-ecology of A. jauari w,as analysed over a period of two years in the Anavilhanas Archipelago, Rio Negro, Brazil, with a focus on phenology, fruit production, and seed dispersal. Fruit fall is annual and synchronized with high water levels, with a production of 1.6 ton of fruit ha-1. The fruits are eaten by at least 16 species of fish which either gnaw the pulp, fragment the seed, or ingest the entire fruit, thus acting as dispersal agents. Besides ichthyocory, barochory (with subsequent vegetative propagation is an important dispersal mode, enhancing the occurrence of large masses of individuals in the Anavilhanas islands and in the region of maximum palm heart extraction near BarcelosAstrocaryum jauari Mart. (Arecaceae es una de las especies más comunes de palma en las llanuras de inundación por las llamadas "aguas negras", aguas ricas en taninos que tienen pocos nutrientes para la fauna. Habita el subdosel que se desarrolla en riberas e islas, con una distribución amplia en toda la gradiente de inundación (resiste entre 30 y 340 días bajo el agua. La especie es importante para la nutrición de los peces y en la producción de palmito. La autoecología de A. jauari fue analizada por dos años en el Archipiélago Anavilhanas, río Negro, Brazil, con énfasis en fenología, producción de frutas, y dispersores de semillas. La caída de los frutos es anual y sincronizada con el aumento de los niveles de agua, con una producción de 1.6 ton de fruta ha-1. Las frutas son comidas por al menos de

  6. Reduced Hornbill Abundance Associated with Low Seed Arrival and Altered Recruitment in a Hunted and Logged Tropical Forest

    OpenAIRE

    Naniwadekar, Rohit; Shukla, Ushma; Isvaran, Kavita; Datta, Aparajita

    2015-01-01

    Logging and hunting are two key direct threats to the survival of wildlife in the tropics, and also disrupt important ecosystem processes. We investigated the impacts of these two factors on the different stages of the seed dispersal cycle, including abundance of plants and their dispersers and dispersal of seeds and recruitment, in a tropical forest in north-east India. We focused on hornbills, which are important seed dispersers in these forests, and their food tree species. We compared abu...

  7. Frugivoría y dispersión de semillas de la palma Oenocarpus bataua (Arecaceae en un bosque de los Andes colombianos Frugivory and seed dispersal Oenocarpus bataua palm (Arecaceae in a forest from the Colombian Andes

    Directory of Open Access Journals (Sweden)

    Rosario Rojas-Robles

    2012-12-01

    Full Text Available En zonas bajas tropicales, en bosques continuos y relativamente poco intervenidos, los frutos de la palma Oenocarpus bataua Mart., son consumidos por diversas especies de vertebrados, sin embargo, no hay estudios de dispersión de más largo plazo con esta especie. Entre agosto 2005-septiembre 2006 se realizaron observaciones de remoción de frutos, conteo de frutos comidos, observaciones focales, registros de frugivoría mediante trampas fotográficas, experimentos de dispersión y parcelas para determinar distribución espacial de Oenocarpus bataua. Cinco especies de mamíferos comen, dispersan, entierran (Sciurus granatensis, Microsciurus mimulus, Dasyprocta punctata y Proechimys sp., tapan (Marmosa robinsoni y llevan a las cuevas (Marmosa robinsoni y Proechimys sp., los frutos de O. bataua, sin dañar la semilla. El 21.7% de los frutos fueron dispersados, 13.2% roídos o pelados, 5.6% tapados, enterrados y llevados a cuevas. La distancia media de remoción de semillas y frutos fue 3.1m, aunque en menor proporción se registraron eventos de dispersión > a 50m. La abundante producción, el tamaño, el peso, la intensa remoción de los frutos por frugívoros, las cortas distancias de dispersión, la ausencia de frugívoros de gran porte disminuidos por cacería y fragmentación, encargados de la dispersión de larga distancia y el aumento de roedores, especialmente ardillas que presionan fuertemente el recurso frutos, generan una lluvia de semillas espacialmente restringida, posiblemente responsable de los patrones de distribución agregados en semillas, plántulas y posteriormente en juveniles y sub-adultos.Seed dispersal is a key process that determines the spatial structure and dynamics of populations of plants, establishes the potential area of recruitment and in this way, the basis for subsequent processes such as predation, germination, competition and growth. The purpose of this research was to identify the guild of frugivores of the

  8. Viability of small seeds found in feces of the Central American tapir on Barro Colorado Island, Panama

    NARCIS (Netherlands)

    Capece, P.I.; Aliaga-Rossel, E.; Jansen, P.A.

    2013-01-01

    Tapirs are known as effective dispersers of large-seeded tree species, but their role in dispersing small-seeded plant species has yet to be established. Tapir feces have been reported to contain large numbers of small seeds, but whether these are viable has rarely been evaluated. We determined the

  9. Diamond Synthesis Employing Nanoparticle Seeds

    Science.gov (United States)

    Uppireddi, Kishore (Inventor); Morell, Gerardo (Inventor); Weiner, Brad R. (Inventor)

    2014-01-01

    Iron nanoparticles were employed to induce the synthesis of diamond on molybdenum, silicon, and quartz substrates. Diamond films were grown using conventional conditions for diamond synthesis by hot filament chemical vapor deposition, except that dispersed iron oxide nanoparticles replaced the seeding. This approach to diamond induction can be combined with dip pen nanolithography for the selective deposition of diamond and diamond patterning while avoiding surface damage associated to diamond-seeding methods.

  10. Seed dispersal of Solanum thomasiifolium Sendtner (Solanaceae in the Linhares Forest, Espírito Santo state, Brazil Dispersão de sementes de Solanum thomasiifolium Sendtner (Solanaceae na Floresta de Linhares, Espírito Santo, Brasil

    Directory of Open Access Journals (Sweden)

    João Vasconcellos-Neto

    2009-12-01

    Full Text Available The aim of this study was to analyse seed dispersal and establishment of Solanum thomasiifolium in an area of "nativo" vegetation in Espirito Santo state on the southeastern Brazilian coast. Ten species of birds, the crab-eating fox (Cerdocyon thous, and one species of lizard (Tropidurus torquatus fed on S. thomasiifolium fruits and dispersed viable seeds in their faeces. The proportional contribution of each of these groups to seed dispersal was 77% (birds, 19% (crab-eating fox and 4% (lizards. Ants also contributed to seed dispersal. More seeds were deposited in vegetation islands than in the surrounding open areas. Germination rates of seeds collected directly from fruit (control, bird droppings, the faeces of crab-eating foxes and lizards were, respectively, 64, 64, 53, and 80 %. Differences among these rates were all significant, except between birds and control. Lizards were important as seed carriers between nearby islands and they expelled a higher proportion of viable seeds. Birds and the crab-eating foxes did not enhance seed germination, but promoted seed dispersal over a wider area. Plant architecture, fruit productivity, fruit characteristics and the diversity of frugivores are important for the success of S. thomasiifolium in habitat colonization.O propósito deste estudo foi analisar a dispersão de sementes e o estabelecimento de Solanum thomasiifolium em uma área de vegetação de "nativo" no Estado do Espírito Santo, na costa do sudeste do Brasil. Dez espécies de aves, o cachorro-do-mato (Cerdocyon thous e uma espécie de lagarto (Tropidurus torquatus alimentaram-se de frutos de S. thomasiifolium e dispersaram sementes viáveis em suas fezes. A contribuição proporcional de cada um destes grupos na dispersão de sementes foi de 77% para aves, 19% para o cachorro-do-mato e 4% para o lagarto. Formigas também contribuíram com a dispersão de sementes. Mais sementes foram depositadas nas ilhas de vegetação do que nas

  11. Burial of Zostera marina seeds in sediment inhabited by three polychaetes: laboratory and field studies

    DEFF Research Database (Denmark)

    Delefosse, Matthieu; Kristensen, Erik

    2012-01-01

    The large number of seeds produced by eelgrass, Zostera marina, provides this plant with a potential to disperse widely and colonise newareas. After dispersal, seedsmust be buried into sediment for assuring long-term survival, successful germination and safe seedling development. Seedsmay be buried...... eelgrass seed bank at the ecosystemscale. Some species have a positive effect by burying seeds to shallow depths and thereby reducing seed predation and facilitating seed germination, while other species bury seeds too deep for successful seed germination and seedling development....... passively by sedimentation or actively through sediment reworking by benthic fauna.We evaluated the effect of three polychaetes on the burial rate and depth of eelgrass seeds. Burial was first measured in controlled laboratory experiments using different densities of Nereis (Hediste) diversicolor (400...

  12. Profiling the Fatty Acids Content of Ornamental Camellia Seeds Cultivated in Galicia by an Optimized Matrix Solid-Phase Dispersion Extraction

    Directory of Open Access Journals (Sweden)

    Carmen Garcia-Jares

    2017-10-01

    Full Text Available Camellia (genus of flowering plants of fam. Theaceae is one of the main crops in Asia, where tea and oil from leaves and seeds have been utilized for thousands of years. This plant is excellently adapted to the climate and soil of Galicia (northwestern Spain and northern Portugal where it is grown not only as an ornamental plant, but to be evaluated as a source of bioactive compounds. In this work, the main fatty acids were extracted from Camellia seeds of four varieties of Camellia: sasanqua, reticulata, japonica and sinensis, by means of matrix-solid phase dispersion (MSPD, and analyzed by gas chromatography (GC with MS detection of the corresponding methyl esters. MSPD constitutes an efficient and greener alternative to conventional extraction techniques, moreover if it is combined with the use of green solvents such as limonene. The optimization of the MSPD extraction procedure has been conducted using a multivariate approach based on strategies of experimental design, which enabled the simultaneous evaluation of the factors influencing the extraction efficiency as well as interactions between factors. The optimized method was applied to characterize the fatty acids profiles of four Camellia varieties seeds, allowing us to compare their fatty acid composition.

  13. Profiling the Fatty Acids Content of Ornamental Camellia Seeds Cultivated in Galicia by an Optimized Matrix Solid-Phase Dispersion Extraction

    Science.gov (United States)

    Garcia-Jares, Carmen; Sanchez-Nande, Marta; Lamas, Juan Pablo; Lores, Marta

    2017-01-01

    Camellia (genus of flowering plants of fam. Theaceae) is one of the main crops in Asia, where tea and oil from leaves and seeds have been utilized for thousands of years. This plant is excellently adapted to the climate and soil of Galicia (northwestern Spain) and northern Portugal where it is grown not only as an ornamental plant, but to be evaluated as a source of bioactive compounds. In this work, the main fatty acids were extracted from Camellia seeds of four varieties of Camellia: sasanqua, reticulata, japonica and sinensis, by means of matrix-solid phase dispersion (MSPD), and analyzed by gas chromatography (GC) with MS detection of the corresponding methyl esters. MSPD constitutes an efficient and greener alternative to conventional extraction techniques, moreover if it is combined with the use of green solvents such as limonene. The optimization of the MSPD extraction procedure has been conducted using a multivariate approach based on strategies of experimental design, which enabled the simultaneous evaluation of the factors influencing the extraction efficiency as well as interactions between factors. The optimized method was applied to characterize the fatty acids profiles of four Camellia varieties seeds, allowing us to compare their fatty acid composition. PMID:29039745

  14. Qualitative aspects of the effectiveness of Culpeo foxes (Lycalopex culpaeus) as dispersers of Prosopis alba (Fabaceae) in a Bolivian dry valley

    Science.gov (United States)

    Maldonado, D. E.; Loayza, A. P.; Garcia, E.; Pacheco, L. F.

    2018-02-01

    Foxes disperse several plant species in arid and semi-arid environments, but their effectiveness as dispersal agents still remains unclear. In this study, we examined qualitative components of the effectiveness of L. culpaeus as a disperser of P. alba seeds in an inter-Andean dry valley of La Paz, Bolivia. Specifically, we determined seed deposition microhabitats, and the probabilities of germination, seed removal and seedling recruitment in these microhabitats. Additionally, we assessed the effect of gut-passage on P. alba germination. We collected 159 scats, which contained a total of 3402 endocarps fragments. Foxes dispersed seeds into two microhabitats: open areas and under woody vegetation, but more frequently in the former. The probability of germination did not differ between gut-passed and control seeds, but control seeds germinated faster than gut-passed ones. The likelihood of removal was greater for endocarps fragments in open microhabitats than under woody vegetation. Only a small percentage of the seeds in each microhabitat germinated, but none survived more than a week. We conclude that although the Culpeo fox can defecate intact P. alba seeds, it does not provide effective dispersal services.

  15. Dispersal and metapopulation stability

    Directory of Open Access Journals (Sweden)

    Shaopeng Wang

    2015-10-01

    Full Text Available Metapopulation dynamics are jointly regulated by local and spatial factors. These factors may affect the dynamics of local populations and of the entire metapopulation differently. Previous studies have shown that dispersal can stabilize local populations; however, as dispersal also tends to increase spatial synchrony, its net effect on metapopulation stability has been controversial. Here we present a simple metapopulation model to study how dispersal, in interaction with other spatial and local processes, affects the temporal variability of metapopulations in a stochastic environment. Our results show that in homogeneous metapopulations, the local stabilizing and spatial synchronizing effects of dispersal cancel each other out, such that dispersal has no effect on metapopulation variability. This result is robust to moderate heterogeneities in local and spatial parameters. When local and spatial dynamics exhibit high heterogeneities, however, dispersal can either stabilize or destabilize metapopulation dynamics through various mechanisms. Our findings have important theoretical and practical implications. We show that dispersal functions as a form of spatial intraspecific mutualism in metapopulation dynamics and that its effect on metapopulation stability is opposite to that of interspecific competition on local community stability. Our results also suggest that conservation corridors should be designed with appreciation of spatial heterogeneities in population dynamics in order to maximize metapopulation stability.

  16. The evolutionary diversification of seed size: using the past to understand the present.

    Science.gov (United States)

    Sims, Hallie J

    2012-05-01

    The Devonian origin of seed plants and subsequent morphological diversification of seeds during the late Paleozoic represents an adaptive radiation into unoccupied ecological niche space. A plant's seed size is correlated with its life-history strategy, growth form, and seed dispersal syndrome. The fossil record indicates that the oldest seed plants had relatively small seeds, but the Mississippian seed size envelope increased significantly with the diversification of larger seeded lineages. Fossil seeds equivalent to the largest extant gymnosperm seeds appeared by the Pennsylvanian, concurrent with morphological diversification of growth forms and dispersal syndromes as well as the clade's radiation into new environments. Wang's Analysis of Skewness indicates that the evolutionary trend of increasing seed size resulted from primarily passive processes in Pennsylvanian seed plants. The distributions of modern angiosperms indicate a more diverse system of active and some passive processes, unbounded by Paleozoic limits; multiple angiosperm lineages independently evolved though the upper and lower bounds. Quantitative measures of preservation suggest that, although our knowledge of Paleozoic seeds is far from complete, the evolutionary trend in seed size is unlikely to be an artifact of taphonomy. © 2012 The Author. Evolution© 2012 The Society for the Study of Evolution.

  17. Effects of rodent species, seed species, and predator cues on seed fate

    Science.gov (United States)

    Sivy, Kelly J.; Ostoja, Steven M.; Schupp, Eugene W.; Durham, Susan

    2011-07-01

    Seed selection, removal and subsequent management by granivorous animals is thought to be a complex interaction of factors including qualities of the seeds themselves (e.g., seed size, nutritional quality) and features of the local habitat (e.g. perceived predator risk). At the same time, differential seed selection and dispersal is thought to have profound effects on seed fate and potentially vegetation dynamics. In a feeding arena, we tested whether rodent species, seed species, and indirect and direct predation cues influence seed selection and handling behaviors (e.g., scatter hoarding versus larder hoarding) of two heteromyid rodents, Ord's kangaroo rat ( Dipodomys ordii) and the Great Basin pocket mouse ( Perognathus parvus). The indirect cue was shrub cover, a feature of the environment. Direct cues, presented individually, were (1) control, (2) coyote ( Canis latrans) vocalization, (3) coyote scent, (4) red fox ( Vulpes vulpes) scent, or (5) short-eared owl ( Asio flammeus) vocalization. We offered seeds of three sizes: two native grasses, Indian ricegrass ( Achnatherum hymenoides) and bluebunch wheatgrass ( Pseudoroegneria spicata), and the non-native cereal rye ( Secale cereale), each in separate trays. Kangaroo rats preferentially harvested Indian ricegrass while pocket mice predominately harvested Indian ricegrass and cereal rye. Pocket mice were more likely to scatter hoard preferred seeds, whereas kangaroo rats mostly consumed and/or larder hoarded preferred seeds. No predator cue significantly affected seed preferences. However, both species altered seed handling behavior in response to direct predation cues by leaving more seeds available in the seed pool, though they responded to different predator cues. If these results translate to natural dynamics on the landscape, the two rodents are expected to have different impacts on seed survival and plant recruitment via their different seed selection and seed handling behaviors.

  18. Evaluation of essential minerals in pumpkin seeds by EDXRF

    International Nuclear Information System (INIS)

    Boaro, Flavia Araujo; Zacari, Cristiane Z.; Scapin, Marcos A.; Aquino, Reginaldo R.

    2013-01-01

    Pumpkin seeds, marketed in the Municipal Market of Sao Paulo, Brazil, were analyzed using the Energy Dispersive of X-ray Fluorescence technique (EDXRF) seeking to evaluate the content of the main essential minerals present in these seeds, and their contribution to human nutrition

  19. Self-organization, scaling and collapse in a coupled automaton model of foragers and vegetation resources with seed dispersal

    International Nuclear Information System (INIS)

    Boyer, D; Lopez-Corona, O

    2009-01-01

    We introduce a model of travelling agents (e.g., frugivorous animals) who feed on randomly located vegetation patches and disperse their seeds, thus modifying the spatial distribution of the resources in the long term. It is assumed that the survival probability of a seed increases with the distance to its parent patch and decreases with the size of the colonized patch. In turn, the foraging agents use a deterministic strategy with memory that makes them visit the largest possible patches accessible within minimal travelling distances. The combination of these interactions produce complex spatio-temporal patterns. If the patches have a small initial size, the vegetation total mass (biomass) increases with time and reaches a maximum corresponding to a self-organized critical state with power-law-distributed patch sizes and Levy-like movement patterns for the foragers. However, this state collapses as the biomass sharply decreases to reach a noisy stationary regime characterized by corrections to scaling. In systems with low plant competition, the efficiency of the foraging rules leads to the formation of heterogeneous vegetation patterns with 1/f α frequency spectra, and contributes, rather counter-intuitively, to lower the biomass levels.

  20. Solubilization of tea seed oil in a food-grade water-dilutable microemulsion.

    Directory of Open Access Journals (Sweden)

    Lingli Deng

    Full Text Available Food-grade microemulsions containing oleic acid, ethanol, Tween 20, and water were formulated as a carrier system for tea seed oil (Camellia oleifera Abel.. The effect of ethanol on the phase behavior of the microemulsion system was clearly reflected in pseudo-ternary diagrams. The solubilization capacity and solubilization efficiency of tea seed oil dispersions were measured along the dilution line at a 70/30 surfactant/oil mass ratio with Tween 20 as the surfactant and oleic acid and ethanol (1:3, w/w as the oil phase. The dispersed phase of the microemulsion (1.5% weight ratio of tea seed oil to the total amount of oil, surfactant, and tea seed oil could be fully diluted with water without phase separation. Differential scanning calorimetry and viscosity measurements indicated that both the carrier and solubilized systems underwent a similar microstructure transition upon dilution. The dispersion phases gradually inverted from the water-in-oil phase ( 45% water along the dilution line.

  1. The relative contribution of genes operating in the S-methylmethionine cycle to methionine metabolism in Arabidopsis seeds.

    Science.gov (United States)

    Cohen, Hagai; Salmon, Asaf; Tietel, Zipora; Hacham, Yael; Amir, Rachel

    2017-05-01

    Enzymes operating in the S -methylmethionine cycle make a differential contribution to methionine synthesis in seeds. In addition, mutual effects exist between the S -methylmethionine cycle and the aspartate family pathway in seeds. Methionine, a sulfur-containing amino acid, is a key metabolite in plant cells. The previous lines of evidence proposed that the S-methylmethionine (SMM) cycle contributes to methionine synthesis in seeds where methionine that is produced in non-seed tissues is converted to SMM and then transported via the phloem into the seeds. However, the relative regulatory roles of the S-methyltransferases operating within this cycle in seeds are yet to be fully understood. In the current study, we generated transgenic Arabidopsis seeds with altered expression of three HOMOCYSTEINE S-METHYLTRANSFERASEs (HMTs) and METHIONINE S-METHYLTRANSFERASE (MMT), and profiled them for transcript and metabolic changes. The results revealed that AtHMT1 and AtHMT3, but not AtHMT2 and AtMMT, are the predominant enzymes operating in seeds as altered expression of these two genes affected the levels of methionine and SMM in transgenic seeds. Their manipulations resulted in adapted expression level of genes participating in methionine synthesis through the SMM and aspartate family pathways. Taken together, our findings provide new insights into the regulatory roles of the SMM cycle and the mutual effects existing between the two methionine biosynthesis pathways, highlighting the complexity of the metabolism of methionine and SMM in seeds.

  2. Camera-trapping and seed-labelling reveals widespread granivory ...

    African Journals Online (AJOL)

    Many plant–animal interactions can be challenging to directly observe, due to species being small, cryptic and/or nocturnal. Previous research on seed predation and dispersal by rodents in the Fynbos Biome of South Africa has relied on indirect evidence, as methods for directly monitoring rodent–seed interactions were ...

  3. Cleaner mites: sanitary mutualism in the miniature ecosystem of neotropical bee nests.

    Science.gov (United States)

    Biani, Natalia B; Mueller, Ulrich G; Wcislo, William T

    2009-06-01

    Cleaning symbioses represent classic models of mutualism, and some bee mites are thought to perform cleaning services for their hosts in exchange for suitable environments for reproduction and dispersal. These mutual benefits, however, have not been rigorously demonstrated. We tested the sanitary role of bee mites by correlating mite loads with fungal contamination in natural nests of Megalopta genalis and Megalopta ecuadoria and by experimentally manipulating mite loads in artificial cells with developing brood. Field observations revealed significant correlations between the presence of mites and the absence of fungi inside the brood cells, as well as between the absence of mites and increased bee mortality. Likewise, experimental brood cells with mites have fewer fungal colonies than do cells without mites. Field observations and experimental manipulations, therefore, provide clear evidence of the sanitary effect of mites in nests of Megalopta bees. This bee-mite association constitutes one of the few examples of terrestrial cleaning mutualisms.

  4. Patterns and mechanisms of dispersal in a keystone seagrass species

    DEFF Research Database (Denmark)

    Jahnke, M.; Christensen, Asbjørn; Micu, D.

    2016-01-01

    •Z. noltei shows low genetic connectivity (from 10 s to 100 s of km) in the Black Sea.•Physical modelling of dispersal well agree with estimates of genetic connectivity.•Physical and genetic connectivity show possible but rare long distance dispersal.•Seeds get dispersed locally while shoots have...

  5. Secondary seed dispersal of Ricinus communis Linnaeus (Euphorbiaceae by ants in secondary growth vegetation in Minas Gerais Dispersão secundária de sementes de Ricinus communis Linnaeus (Euphorbiaceae por formigas em vegetação secundária em Minas Gerais

    Directory of Open Access Journals (Sweden)

    Mário Marcos do Espírito Santo

    2007-12-01

    Full Text Available In this study, I tested the efficacy of ants as secondary seed dispersers of Ricinus communis in southeastern Brazil. In a natural population of 143 individuals, I determined the ballistic dispersal distance for 62 seeds and 100 additional seeds were experimentally offered to ants in groups of ten seeds along a transect of 50 m. Fifty-three seeds were removed by ants, mainly by the leafcutter Atta sexdens (90.4%. The dispersal distance by ants was high, compared to the global average (4.38 m ± 0.74 m vs. 0.96 m, but was lower than the ballistic distance (7.27 m ± 0.13 m. Ants increased the total dispersal distance (8.66 m ± 0.60 m, but the main benefit for the plant was the directed dispersal, with seed deposition on the enriched soil of ant nests.Este estudo testou a eficiência de formigas como dispersores secundários de Ricinus communis no Brasil. Em uma população natural de 143 indivíduos, a distância de dispersão balística foi determinada para 62 sementes. Além disso, 100 sementes adicionais foram oferecidas a formigas em grupos de 10, ao longo de um transecto de 50 m. Cinqüenta e três sementes foram removidas por formigas, principalmente pela formiga-cortadeira Atta sexdens (90,4%. A distância de dispersão por formigas foi alta se comparada à média global (4,38m ± 0,74 m vs. 0,96 m, porém menor que a distância de dispersão balística (7,27 m ± 0,13 m. As formigas aumentaram a distância de dispersão total (8,66 m ± 0,60 m, mas o principal benefício para a planta foi a dispersão direcionada, com a deposição das sementes no solo enriquecido encontrado nos ninhos das formigas.

  6. Seed rain under native and non-native tree species in the Cabo Rojo National Wildlife Refuge, Puerto Rico.

    Science.gov (United States)

    Arias Garcia, Andrea; Chinea, J Danilo

    2014-09-01

    Seed dispersal is a fundamental process in plant ecology and is of critical importance for the restoration of tropical communities. The lands of the Cabo Rojo National Wildlife Refuge (CRNWR), formerly under agriculture, were abandoned in the 1970s and colonized mainly by non-native tree species of degraded pastures. Here we described the seed rain under the most common native and non-native trees in the refuge in an attempt to determine if focal tree geographic origin (native versus non-native) influences seed dispersal. For this, seed rain was sampled for one year under the canopies of four native and four non-native tree species common in this refuge using 40 seed traps. No significant differences were found for the abundance of seeds, or their diversity, dispersing under native versus non-native focal tree species, nor under the different tree species. A significantly different seed species composition was observed reaching native versus non-native focal species. However, this last result could be more easily explained as a function of distance of the closest adults of the two most abundantly dispersed plant species to the seed traps than as a function of the geographic origin of the focal species. We suggest to continue the practice of planting native tree species, not only as a way to restore the community to a condition similar to the original one, but also to reduce the distances needed for effective dispersal.

  7. Contrasting germination responses to vegetative canopies experienced in pre- vs. post-dispersal environments

    Science.gov (United States)

    Leverett, Lindsay D.; Auge, Gabriela A.; Bali, Aman; Donohue, Kathleen

    2016-01-01

    Background Seeds adjust their germination based on conditions experienced before and after dispersal. Post-dispersal cues are expected to be more accurate predictors of offspring environments, and thus offspring success, than pre-dispersal cues. Therefore, germination responses to conditions experienced during seed maturation may be expected to be superseded by responses to conditions experienced during seed imbibition. In taxa of disturbed habitats, neighbours frequently reduce the performance of germinants. This leads to the hypotheses that a vegetative canopy will reduce germination in such taxa, and that a vegetative canopy experienced during seed imbibition will over-ride germination responses to a canopy experienced during seed maturation, since it is a more proximal cue of immediate competition. These hypotheses were tested here in Arabidopsis thaliana. Methods Seeds were matured under a simulated canopy (green filter) or white light. Fresh (dormant) seeds were imbibed in the dark, white light or canopy at two temperatures (10 or 22 °C), and germination proportions were recorded. Germination was also recorded in after-ripened (less dormant) seeds that were induced into secondary dormancy and imbibed in the dark at each temperature, either with or without brief exposure to red and far-red light. Key Results Unexpectedly, a maturation canopy expanded the conditions that elicited germination, even as seeds lost and regained dormancy. In contrast, an imbibition canopy impeded or had no effect on germination. Maturation under a canopy did not modify germination responses to red and far-red light. Seed maturation under a canopy masked genetic variation in germination. Conclusions The results challenge the hypothesis that offspring will respond more strongly to their own environment than to that of their parents. The observed relaxation of germination requirements caused by a maturation canopy could be maladaptive for offspring by disrupting germination responses

  8. Seed maturation in Arabidopsis is characterised by nuclear size reduction and increased chromatin condensation

    NARCIS (Netherlands)

    Zanten, van M.; Koini, M.A.; Geyer, R.; Liu, Y.; Brambilla, V.; Bartels, D.; Koornneef, M.; Fransz, P.; Soppe, W.J.J.

    2011-01-01

    Most plant species rely on seeds for their dispersal and survival under unfavorable environmental conditions. Seeds are characterized by their low moisture content and significantly reduced metabolic activities. During the maturation phase, seeds accumulate storage reserves and become

  9. Limited gene dispersal and spatial genetic structure as stabilizing factors in an ant-plant mutualism.

    Science.gov (United States)

    Malé, P-J G; Leroy, C; Humblot, P; Dejean, A; Quilichini, A; Orivel, J

    2016-12-01

    Comparative studies of the population genetics of closely associated species are necessary to properly understand the evolution of these relationships because gene flow between populations affects the partners' evolutionary potential at the local scale. As a consequence (at least for antagonistic interactions), asymmetries in the strength of the genetic structures of the partner populations can result in one partner having a co-evolutionary advantage. Here, we assess the population genetic structure of partners engaged in a species-specific and obligatory mutualism: the Neotropical ant-plant, Hirtella physophora, and its ant associate, Allomerus decemarticulatus. Although the ant cannot complete its life cycle elsewhere than on H. physophora and the plant cannot live for long without the protection provided by A. decemarticulatus, these species also have antagonistic interactions: the ants have been shown to benefit from castrating their host plant and the plant is able to retaliate against too virulent ant colonies. We found similar short dispersal distances for both partners, resulting in the local transmission of the association and, thus, inbred populations in which too virulent castrating ants face the risk of local extinction due to the absence of H. physophora offspring. On the other hand, we show that the plant populations probably experienced greater gene flow than did the ant populations, thus enhancing the evolutionary potential of the plants. We conclude that such levels of spatial structure in the partners' populations can increase the stability of the mutualistic relationship. Indeed, the local transmission of the association enables partial alignments of the partners' interests, and population connectivity allows the plant retaliation mechanisms to be locally adapted to the castration behaviour of their symbionts. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

  10. Topographic separation of two sympatric palms in the central Amazon - does dispersal play a role?

    Science.gov (United States)

    Gomes de Freitas, Cintia; Capellotto Costa, Flávia Regina; Svenning, Jens-Christian; Balslev, Henrik

    2012-02-01

    Despite broadly overlapping geographic distributions in the central Amazon basin, two congeneric palm species (Attalea attaleoides and Attalea microcarpa) have topographically separated distributions on a local scale in Reserva Ducke near Manaus. Our aim here was to determine if this local scale separation can be linked to (1) seedling stage specialization to different habitat conditions of the two species, and/or (2) environmentally-controlled seed dispersal. We assessed the role of these potential drivers by mapping the local distribution of the two species over a 25-km2 grid and testing for correlation to seed removal and seed germination patterns using seed sowing experiments. 360 seeds of each species were sown in 30 uniformly distributed plots (12 seeds of each species in each plot), and seed removal and germination were subsequently monitored. Adult populations of the two species showed opposite distribution patterns linked to topography. However, there was little evidence for specialization to different habitat conditions at the seedling stage: after 11 months, 26.1% of seeds of A. microcarpa had germinated along the entire topographic gradient, albeit with a tendency toward higher germination in more inclined areas. For A. attaleoides, only 2.2% seeds had germinated, and again along the entire topographic gradient. In contrast, there was evidence for environmentally-controlled seed dispersal: for both species, seed removal was higher in flat areas. Presence of adults did not affect germination or seed removal. Our results suggest that topographically differentiated distributions of A. attaleoides and A. microcarpa may be reinforced by steep slope avoidance by their seed dispersers. A direct environmental control mechanism remains to be identified to explain the consistent topographic associations, but our results show that this mechanism does not work at the seed germination stage.

  11. Fruit and seed heteromorphism in the cold desert annual ephemeral Diptychocarpus strictus (Brassicaceae) and possible adaptive significance.

    Science.gov (United States)

    Lu, Juanjuan; Tan, Dunyan; Baskin, Jerry M; Baskin, Carol C

    2010-06-01

    Diptychocarpus strictus is an annual ephemeral in the cold desert of northwest China that produces heteromorphic fruits and seeds. The primary aims of this study were to characterize the morphology and anatomy of fruits and seeds of this species and compare the role of fruit and seed heteromorphism in dispersal and germination. Shape, size, mass and dispersal of siliques and seeds and the thickness of the mucilage layer on seeds were measured, and the anatomy of siliques and seeds, the role of seed mucilage in water absorption/dehydration, germination and adherence of seeds to soil particles, the role of pericarp of lower siliques in seed dormancy and seed after-ripening and germination phenology were studied using standard procedures. Plants produce dehiscent upper siliques with a thin pericarp containing seeds with large wings and a thick mucilage layer and indehiscent lower siliques with a thick pericarp containing nearly wingless seeds with a thin mucilage layer. The dispersal ability of seeds from the upper siliques was much greater than that of intact lower siliques. Mucilage increased the amount of water absorbed by seeds and decreased the rate of dehydration. Seeds with a thick mucilage layer adhered to soil particles much better than those with a thin mucilage layer or those from which mucilage had been removed. Fresh seeds were physiologically dormant and after-ripened during summer. Non-dormant seeds germinated to high percentages in light and in darkness. Germination of seeds from upper siliques is delayed until spring primarily by drought in summer and autumn, whereas the thick, indehiscent pericarp prevents germination for >1 year of seeds retained in lower siliques. The life cycle of D. strictus is morphologically and physiologically adapted to the cold desert environment in time and space via a combination of characters associated with fruit and seed heteromorphism.

  12. Seed maturation in Arabidopsis thaliana is characterized by nuclear size reduction and increased chromatin condensation

    NARCIS (Netherlands)

    van Zanten, M.; Koini, M. A.; Geyer, R.; Liu, Y.; Brambilla, V.; Bartels, D.; Koornneef, M.; Fransz, P.; Soppe, W. J.

    2011-01-01

    Most plant species rely on seeds for their dispersal and survival under unfavorable environmental conditions. Seeds are characterized by their low moisture content and significantly reduced metabolic activities. During the maturation phase, seeds accumulate storage reserves and become

  13. “Sticky invasion” – the physical properties of Plantago lanceolata L. seed mucilage

    Directory of Open Access Journals (Sweden)

    Agnieszka Kreitschitz

    2016-12-01

    Full Text Available The mucilage envelope of seeds has various functions including the provision of different ways for the dispersal of diaspores. Chemical composition and water content of the mucilage yield particular adhesive and frictional properties in the envelope that also influence the dispersal of seeds. To determine the physical properties of Plantago lanceolata seed mucilage we studied (1 composition, (2 desiccation, (3 adhesion, and (4 friction properties of the mucilage under different hydration conditions. We revealed the presence of cellulose fibrils in the mucilage, which are responsible for a continuous and even distribution of the mucilaginous layer on the seed surface. The measured values of adhesive and frictional properties differed significantly in comparison to the previously studied pectic mucilage of Linum usitatissimum. Also, the water loss from the cellulose mucilage was more rapid. The obtained different values can result from the presence of cellulose fibrils and their interaction with pectins in the mucilage. Because of this feature the mucilage of P. lanceolata may represent a more regularly ordered and stabile system than the pectic mucilage of flax, which lacks cellulose. In spite of the fact that P. lanceolata mucilage revealed different adhesive and frictional properties than the pectic mucilage, it still demonstrates an effective system promoting zoochoric seed dispersal. Cellulose may additionally prevent the mucilage against loss from the seed surface.

  14. Bird Perches Increase Forest Seeds on Puerto Rican Landslides.

    Science.gov (United States)

    Aaron B. Shiels; Lawrence R. Walker

    2003-01-01

    Landslides result in the loss of vertical vegetative structure, soil nutrients, and the soil seed bank. These losses impede timely recovery of tropical forest communities. In this study we added bird perches to six Puerto Rican landslides with three types of surfaces (bare, climbing fern, grass) in an effort to facilitate inputs of forest seeds through bird dispersal...

  15. The missing part of seed dispersal networks: structure and robustness of bat-fruit interactions.

    Directory of Open Access Journals (Sweden)

    Marco Aurelio Ribeiro Mello

    2011-02-01

    Full Text Available Mutualistic networks are crucial to the maintenance of ecosystem services. Unfortunately, what we know about seed dispersal networks is based only on bird-fruit interactions. Therefore, we aimed at filling part of this gap by investigating bat-fruit networks. It is known from population studies that: (i some bat species depend more on fruits than others, and (ii that some specialized frugivorous bats prefer particular plant genera. We tested whether those preferences affected the structure and robustness of the whole network and the functional roles of species. Nine bat-fruit datasets from the literature were analyzed and all networks showed lower complementary specialization (H(2' = 0.37±0.10, mean ± SD and similar nestedness (NODF = 0.56±0.12 than pollination networks. All networks were modular (M = 0.32±0.07, and had on average four cohesive subgroups (modules of tightly connected bats and plants. The composition of those modules followed the genus-genus associations observed at population level (Artibeus-Ficus, Carollia-Piper, and Sturnira-Solanum, although a few of those plant genera were dispersed also by other bats. Bat-fruit networks showed high robustness to simulated cumulative removals of both bats (R = 0.55±0.10 and plants (R = 0.68±0.09. Primary frugivores interacted with a larger proportion of the plants available and also occupied more central positions; furthermore, their extinction caused larger changes in network structure. We conclude that bat-fruit networks are highly cohesive and robust mutualistic systems, in which redundancy is high within modules, although modules are complementary to each other. Dietary specialization seems to be an important structuring factor that affects the topology, the guild structure and functional roles in bat-fruit networks.

  16. Host specificity, phenotype matching and the evolution of reproductive isolation in a coevolved plant-pollinator mutualism.

    Science.gov (United States)

    Himler, Anna G; Machado, Carlos A

    2009-12-01

    Coevolutionary interactions between plants and their associated pollinators and seed dispersers are thought to have promoted the diversification of flowering plants (Raven 1977; Regal 1977; Stebbins 1981). The actual mechanisms by which pollinators could drive species diversification in plants are not fully understood. However, it is thought that pollinator host specialization can influence the evolution of reproductive isolation among plant populations because the pollinator's choice of host is what determines patterns of gene flow in its host plant, and host choice may also have important consequences on pollinator and host fitness (Grant 1949; Bawa 1992). In this issue of Molecular Ecology, Smith et al. (2009) present a very interesting study that addresses how host specialization affects pollinator fitness and patterns of gene flow in a plant host. Several aspects of this study match elements of a seminal mathematical model of plant-pollinator codivergence (Kiester et al. 1984) suggesting that reciprocal selection for matched plant and pollinator reproductive traits may lead to speciation in the host and its pollinator when there is strong host specialization and a pattern of geographic subdivision. Smith et al.'s study represents an important step to fill the gap in our understanding of how reciprocal selection may lead to speciation in coevolved plant-pollinator mutualisms.

  17. Seasonal rhythms of seed rain and seedling emergence in two tropical rain forests in southern Brazil.

    Science.gov (United States)

    Marques, M C M; Oliveira, P E A M

    2008-09-01

    Seasonal tropical forests show rhythms in reproductive activities due to water stress during dry seasons. If both seed dispersal and seed germination occur in the best environmental conditions, mortality will be minimised and forest regeneration will occur. To evaluate whether non-seasonal forests also show rhythms, for 2 years we studied the seed rain and seedling emergence in two sandy coastal forests (flooded and unflooded) in southern Brazil. In each forest, one 100 x 30-m grid was marked and inside it 30 stations comprising two seed traps (0.5 x 0.5 m each) and one plot (2 x 2 m) were established for monthly monitoring of seed rain and a seedling emergence study, respectively. Despite differences in soil moisture and incident light on the understorey, flooded and unflooded forests had similar dispersal and germination patterns. Seed rain was seasonal and bimodal (peaks at the end of the wetter season and in the less wet season) and seedling emergence was seasonal and unimodal (peaking in the wetter season). Approximately 57% of the total species number had seedling emergence 4 or more months after dispersal. Therefore, both seed dormancy and the timing of seed dispersal drive the rhythm of seedling emergence in these forests. The peak in germination occurs in the wetter season, when soil fertility is higher and other phenological events also occur. The strong seasonality in these plant communities, even in this weakly seasonal climate, suggests that factors such as daylength, plant sensitivity to small changes in the environment (e.g. water and nutrient availability) or phylogenetic constraints cause seasonal rhythms in the plants.

  18. Factoring the dispersion relation in the presence of Lorentz violation

    International Nuclear Information System (INIS)

    Colladay, Don; McDonald, Patrick; Mullins, David

    2010-01-01

    We produce an explicit formula for the dispersion relation for the Dirac equation in the standard model extension in the presence of Lorentz violation. Our expression is obtained using novel techniques which exploit the algebra of quaternions. The dispersion relation is found to conveniently factor in two special cases that each involve a mutually exclusive set of nonvanishing Lorentz-violating parameters. This suggests that a useful approach to studies of Lorentz-violating models is to split the parameter space into two separate pieces, each of which yields a simple, tractable dispersion relation that can be used for analysis.

  19. Seed dormancy and germination.

    Science.gov (United States)

    Penfield, Steven

    2017-09-11

    Reproduction is a critical time in plant life history. Therefore, genes affecting seed dormancy and germination are among those under strongest selection in natural plant populations. Germination terminates seed dispersal and thus influences the location and timing of plant growth. After seed shedding, germination can be prevented by a property known as seed dormancy. In practise, seeds are rarely either dormant or non-dormant, but seeds whose dormancy-inducing pathways are activated to higher levels will germinate in an ever-narrower range of environments. Thus, measurements of dormancy must always be accompanied by analysis of environmental contexts in which phenotypes or behaviours are described. At its simplest, dormancy can be imposed by the formation of a simple physical barrier around the seed through which gas exchange and the passage of water are prevented. Seeds featuring this so-called 'physical dormancy' often require either scarification or passage through an animal gut (replete with its associated digestive enzymes) to disrupt the barrier and permit germination. In other types of seeds with 'morphological dormancy' the embryo remains under-developed at maturity and a dormant phase exists as the embryo continues its growth post-shedding, eventually breaking through the surrounding tissues. By far, the majority of seeds exhibit 'physiological dormancy' - a quiescence program initiated by either the embryo or the surrounding endosperm tissues. Physiological dormancy uses germination-inhibiting hormones to prevent germination in the absence of the specific environmental triggers that promote germination. During and after germination, early seedling growth is supported by catabolism of stored reserves of protein, oil or starch accumulated during seed maturation. These reserves support cell expansion, chloroplast development and root growth until photoauxotrophic growth can be resumed. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

  20. Limits of selection against cheaters: birds prioritise visual fruit advertisement over taste.

    Science.gov (United States)

    Wang, Zhen; Schaefer, H Martin

    2014-04-01

    The concept of biological markets aims to explain how organisms interact with each other. Market theory predicts that organisms choose the most rewarding partner in mutualisms. However, partner choice may also be influenced by advertisement which may not be reliable. In seed dispersal mutualism, we analysed whether seed dispersers prioritise taste cues over visual advertisement to select the most rewarding fruits and whether they select against partners with unreliable advertisement. We conducted experiments on black elder (Sambucus nigra), a species of which the colours of the peduncles match the sugar content of their fruits. We created infructescences the colours of which matched or mismatched the sugar content of their fruits. There was no selection against cheaters in the field or by captive blackcaps (Sylvia atricapilla) as seed dispersers. Blackcaps were constrained to select against unreliable advertisement because they swallowed fruits entirely and thus did not obtain an immediate feedback by taste. Instead, blackcaps selected fruits according to the colour variation of red peduncles. Overall, we suggest that the concept of constraints should be incorporated into biological markets. We further contend that biological markets can be more complex than currently acknowledged because a moderate degree of reliability occurred in black elder even in the absence of selection against cheaters.

  1. Minimizing Mutual Couping

    DEFF Research Database (Denmark)

    2010-01-01

    Disclosed herein are techniques, systems, and methods relating to minimizing mutual coupling between a first antenna and a second antenna.......Disclosed herein are techniques, systems, and methods relating to minimizing mutual coupling between a first antenna and a second antenna....

  2. Between-Site Differences in the Scale of Dispersal and Gene Flow in Red Oak

    Science.gov (United States)

    Emily V Moran; James S. Clark

    2012-01-01

    Background: Nut-bearing trees, including oaks (Quercus spp.), are considered to be highly dispersal limited, leading to concerns about their ability to colonize new sites or migrate in response to climate change. However, estimating seed dispersal is challenging in species that are secondarily dispersed by animals, and differences in...

  3. Dispersal limitation in epiphytic bromeliad communities in a Costa Rican fragmented montane landscape

    NARCIS (Netherlands)

    Cascante-Marin, A.; von Meijenfeldt, N.; de Leeuw, H.M.H.; Wolf, J.H.D.; Oostermeijer, J.G.B.; den Nijs, J.C.M.

    2009-01-01

    Transformation of tropical forests is likely to affect seed-dispersal patterns and influence the composition of epiphytic plant communities in human-altered habitats. We tested this hypothesis by carrying out a comparative study of seed influx, survival and growth of transplanted seedlings of

  4. A functional analysis of cell cycle events in developing and germinating tomato seeds

    NARCIS (Netherlands)

    Castro, de R.D.

    1998-01-01

    Seeds are complex biological structures and the primary dispersal units of higher plants. They consist of nutrient reserve storage tissue(s), an embryo and encapsulating structures designated for protection and that may also regulate germination. Seeds have developed mechanisms of

  5. GROWTH OF A LOCALIZED SEED MAGNETIC FIELD IN A TURBULENT MEDIUM

    International Nuclear Information System (INIS)

    Cho, Jungyeon; Yoo, Hyunju

    2012-01-01

    Turbulence dynamo deals with the amplification of a seed magnetic field in a turbulent medium and has been studied mostly for uniform or spatially homogeneous seed magnetic fields. However, some astrophysical processes (e.g., jets from active galaxies, galactic winds, or ram-pressure stripping in galaxy clusters) can provide localized seed magnetic fields. In this paper, we numerically study amplification of localized seed magnetic fields in a turbulent medium. Throughout the paper, we assume that the driving scale of turbulence is comparable to the size of the system. Our findings are as follows. First, turbulence can amplify a localized seed magnetic field very efficiently. The growth rate of magnetic energy density is as high as that for a uniform seed magnetic field. This result implies that magnetic field ejected from an astrophysical object can be a viable source of a magnetic field in a cluster. Second, the localized seed magnetic field disperses and fills the whole system very fast. If turbulence in a system (e.g., a galaxy cluster or a filament) is driven at large scales, we expect that it takes a few large-eddy turnover times for the magnetic field to fill the whole system. Third, growth and turbulence diffusion of a localized seed magnetic field are also fast in high magnetic Prandtl number turbulence. Fourth, even in decaying turbulence, a localized seed magnetic field can ultimately fill the whole system. Although the dispersal rate of the magnetic field is not fast in purely decaying turbulence, it can be enhanced by an additional forcing.

  6. 26 CFR 1.831-1 - Tax on insurance companies (other than life or mutual), mutual marine insurance companies, and...

    Science.gov (United States)

    2010-04-01

    ... mutual), mutual marine insurance companies, and mutual fire insurance companies issuing perpetual... companies (other than life or mutual), mutual marine insurance companies, and mutual fire insurance... insurance companies and mutual fire insurance companies exclusively issuing either perpetual policies, or...

  7. Seeding black holes in cosmological simulations

    Science.gov (United States)

    Taylor, P.; Kobayashi, C.

    2014-08-01

    We present a new model for the formation of black holes in cosmological simulations, motivated by the first star formation. Black holes form from high density peaks of primordial gas, and grow via both gas accretion and mergers. Massive black holes heat the surrounding material, suppressing star formation at the centres of galaxies, and driving galactic winds. We perform an investigation into the physical effects of the model parameters, and obtain a `best' set of these parameters by comparing the outcome of simulations to observations. With this best set, we successfully reproduce the cosmic star formation rate history, black hole mass-velocity dispersion relation, and the size-velocity dispersion relation of galaxies. The black hole seed mass is ˜103 M⊙, which is orders of magnitude smaller than that which has been used in previous cosmological simulations with active galactic nuclei, but suggests that the origin of the seed black holes is the death of Population III stars.

  8. Mutual capacitor and its applications

    Directory of Open Access Journals (Sweden)

    Chun Li

    2014-06-01

    Full Text Available This study presents a new ac circuit element – the mutual capacitor, being a dual of the mutual inductor, which is also a new ac transformer. This element is characteristic of the mutual-capacitance coupling of a multi-capacitance system. A unity-coupled mutual capacitor works as an ideal current or voltage transformer, and incidentally acts as waveform separating when inductor employed or waveform converting from square-wave to quasi-sine or waveform filtering, between ports. As a transformer, the mutual capacitor is easy to design, easy for heat cooling, more accurate for current or voltage transformation, dissipating less energy as well as saving materials, suitable for high-power and high-voltage applications. Experiments to demonstrate performances of unity-coupled mutual capacitors are also given.

  9. DISPERSAL OF SEEDS AS NEST MATERIAL BY THE CACTUS WREN

    Science.gov (United States)

    Cactus wren (Campylorhynchus brunneicapillus) nests from the southern Chihuahuan Desert contained viable seeds of grasses, forbs, and shrubs. The most common plants used as construction material in these nests were Muhlenbergia porteri, Boerhavia spicata, and the alien grass Era...

  10. Seed-deposition and recruitment patterns of Clusia species in a disturbed tropical montane forest in Bolivia

    Science.gov (United States)

    Saavedra, Francisco; Hensen, Isabell; Apaza Quevedo, Amira; Neuschulz, Eike Lena; Schleuning, Matthias

    2017-11-01

    Spatial patterns of seed dispersal and recruitment of fleshy-fruited plants in tropical forests are supposed to be driven by the activity of animal seed dispersers, but the spatial patterns of seed dispersal, seedlings and saplings have rarely been analyzed simultaneously. We studied seed deposition and recruitment patterns of three Clusia species in a tropical montane forest of the Bolivian Andes and tested whether these patterns changed between habitat types (forest edge vs. forest interior), distance to the fruiting tree and consecutive recruitment stages of the seedlings. We recorded the number of seeds deposited in seed traps to assess the local seed-deposition pattern and the abundance and distribution of seedlings and saplings to evaluate the spatial pattern of recruitment. More seeds were removed and deposited at the forest edge than in the interior. The number of deposited seeds decreased with distance from the fruiting tree and was spatially clustered in both habitat types. The density of 1-yr-old seedlings and saplings was higher at forest edges, whereas the density of 2-yr-old seedlings was similar in both habitat types. While seedlings were almost randomly distributed, seeds and saplings were spatially clustered in both habitat types. Our findings demonstrate systematic changes in spatial patterns of recruits across the plant regeneration cycle and suggest that the differential effects of biotic and abiotic factors determine plant recruitment at the edges and in the interior of tropical montane forests. These differences in the spatial distribution of individuals across recruitment stages may have strong effects on plant community dynamics and influence plant species coexistence in disturbed tropical forests.

  11. Seed rain dynamics following disturbance exclusion in a secondary tropical dry forest in Morelos, Mexico.

    Science.gov (United States)

    Ceccon, Eliane; Hernández, Patricia

    2009-01-01

    In most of the legally protected areas in Mexico local inhabitants use natural resources, such as fire wood or cattle grazing. These frequent but low-intensity disturbances have consequences at various levels of the tropical ecosystems and strongly impact forest structure and its regeneration capacity. Despite their importance, the effects of these perturbations in many aspects of tropical forest ecology and in the forest's capacity to recover after disturbance exclusion remain poorly understood. Understanding the impact of these processes on tropical forests is necessary for rehabilitating these forests and enhancing their productivity. In this study, we evaluate the impact of twelve years of exclusion (E) of cattle grazing and fire wood extraction in the composition and dynamics of seed rain, and compare this assessment to a similar analysis in an area where these perturbations continued (without exclusion, WE). We found a strong seasonality in seed rain (96% of seeds fell in the dry season) in both areas. There were no significant differences between E and WE sites in relation to overall seed density, species richness and diversity. However, the distribution along the year of seed species density was significantly different among the E and WE sites. The Jaccard's similarity index between E and WE sites was relatively low (0.57). Barochory was the most common dispersal mode observed among the 23 species in terms of seed species density (48%), followed by anemochory (39%) and zoochory (13%). In relation to seed density, anemochory was the most frequent dispersal mode (88%). Most species in the zone were categorized as small seeds (92%), and there were no significant differences in the distribution of seed size between E and WE. The spatial pattern of dispersal of the four species with the highest relative importance value index, in both areas, was aggregated. Twelve years of disturbance exclusion were not enough to fully restore the seed rain of the area; some

  12. Seed dispersal and establishment of endangered plants on Oceanic Islands: the Janzen-Connell model, and the use of ecological analogues.

    Directory of Open Access Journals (Sweden)

    Dennis M Hansen

    Full Text Available BACKGROUND: The Janzen-Connell model states that plant-specific natural enemies may have a disproportionately large negative effect on progeny close to maternal trees. The majority of experimental and theoretical studies addressing the Janzen-Connell model have explored how it can explain existing patterns of species diversity in tropical mainland areas. Very few studies have investigated how the model's predictions apply to isolated oceanic islands, or to the conservation management of endangered plants. Here, we provide the first experimental investigation of the predictions of the Janzen-Connell model on an oceanic island, in a conservation context. In addition, we experimentally evaluate the use of ecological analogue animals to resurrect the functional component of extinct frugivores that could have dispersed seeds away from maternal trees. METHODOLOGY/PRINCIPAL FINDINGS: In Mauritius, we investigated seed germination and seedling survival patterns of the critically endangered endemic plant Syzygium mamillatum (Myrtaceae in relation to proximity to maternal trees. We found strong negative effects of proximity to maternal trees on growth and survival of seedlings. We successfully used giant Aldabran tortoises as ecological analogues for extinct Mauritian frugivores. Effects of gut-passage were negative at the seed germination stage, but seedlings from gut-passed seeds grew taller, had more leaves, and suffered less damage from natural enemies than any of the other seedlings. CONCLUSIONS/SIGNIFICANCE: We provide the first experimental evidence of a distance-dependent Janzen-Connell effect on an oceanic island. Our results potentially have serious implications for the conservation management of rare plant species on oceanic islands, which harbour a disproportionately large fraction of the world's endemic and endangered plants. Furthermore, in contrast to recent controversy about the use of non-indigenous extant megafauna for re

  13. Interaction between parental environment and genotype affects plant and seed performance in Arabidopsis

    NARCIS (Netherlands)

    He, H.; Souza Vidigal, De D.; Snoek, L.B.; Schnabel, S.K.; Nijveen, H.; Hilhorst, H.; Bentsink, L.

    2014-01-01

    Seed performance after dispersal is highly dependent on parental environmental cues, especially during seed formation and maturation. Here we examine which environmental factors are the most dominant in this respect and whether their effects are dependent on the genotypes under investigation. We

  14. Ecological systems as computer networks: Long distance sea dispersal as a communication medium between island plant populations.

    Science.gov (United States)

    Sanaa, Adnen; Ben Abid, Samir; Boulila, Abdennacer; Messaoud, Chokri; Boussaid, Mohamed; Ben Fadhel, Najeh

    2016-06-01

    Ecological systems are known to exchange genetic material through animal species migration and seed dispersal for plants. Isolated plant populations have developed long distance dispersal as a means of propagation which rely on meteorological such as anemochory and hydrochory for coast, island and river bank dwelling species. Long distance dispersal by water, in particular, in the case of water current bound islands, calls for the analogy with computer networks, where each island and nearby mainland site plays the role of a network node, the water currents play the role of a transmission channel, and water borne seeds as data packets. In this paper we explore this analogy to model long distance dispersal of seeds among island and mainland populations, when traversed with water currents, in order to model and predict their future genetic diversity. The case of Pancratium maritimum L. populations in Tunisia is used as a proof of concept, where their genetic diversity is extrapolated. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  15. Leaf litter is essential for seed survival of the endemic endangered tree Pouteria splendens (Sapotaceae from central Chile

    Directory of Open Access Journals (Sweden)

    G. J. Sotes

    2018-01-01

    Full Text Available Pouteria splendens (A.DC. Kuntze, the Chilean lúcumo, is an endemic tree and the only member of the Sapotaceae family in Chile. It is considered an endangered species as a consequence of its restricted distribution and small population size. Currently, individuals of P. splendens are immersed in a heterogeneous landscape with rocky mounds and plains located in areas densely populated by humans. Natural regeneration in the species seems to be low, despite the fact that plants are able to produce fruits. The species produces brightly colored fleshy drupes. There is no information about the dispersal pattern and the fate of the seeds. In this work we investigate (i the seed dispersal pattern and (ii the effect of tree canopy and the presence of leaf litter on seed survival, both in rocky mounds and plains. Results indicated an extremely low distance of seed dispersal, with most of the seeds falling down under the canopy. Seed survival under the canopy without leaf litter was very low and even zero in rocky mounds. Nevertheless, the presence of leaf litter covering the seeds increased survival in both habitats. Outside the canopy, seed survival only increased in plains. We suggest that future conservation programs should focus on protecting both adult plants and leaf litter under trees.

  16. Evolution of mutualism between species

    Energy Technology Data Exchange (ETDEWEB)

    Post, W.M.; Travis, C.C.; DeAngelis, D.L.

    1980-01-01

    Recent theoretical work on mutualism, the interaction between species populations that is mutually beneficial, is reviewed. Several ecological facts that should be addressed in the construction of dynamic models for mutualism are examined. Basic terminology is clarified. (PSB)

  17. Annual losses of weed seeds due to predation in organic cereal fields

    NARCIS (Netherlands)

    Westerman, P.R.; Wes, J.S.; Kropff, M.J.; Werf, van der W.

    2003-01-01

    1. Post-dispersal seed losses in annual arable weed species are poorly quantified, but may be of significance for natural population control, especially if they can be manipulated. We hypothesized that weed seed predation on the soil surface was significant, so we measured rates in the field to

  18. Changes in seed rain across Atlantic Forest fragments in Northeast Brazil

    Science.gov (United States)

    Freitas, Cíntia Gomes; Dambros, Cristian; Camargo, José Luís Campana

    2013-11-01

    The objectives of this study were to characterize the distribution of seeds in remnant fragments of the Atlantic Coastal Forest and to determine whether the species diversity, seed weight, and species composition of plant communities are altered by forest fragmentation. A transect of 100 m was established in the core of each of nine fragments of Atlantic Coastal Forest in a private sugarcane plantation in the state of Alagoas, NE Brazil, and ten seed-traps were distributed at intervals of 10 m each along the transects. For 12 consecutive months seeds were collected, dried, counted, weighed, and identified to species. Seeds were assigned to categories according to their size, dispersal mode, and shade tolerance. Multiple regression models and Mantel correlation tests were used to detect the effects of fragment size, percent forest cover nearby, distance from the source area, and distance from the nearest fragment on species diversity, mean seed weight, and species similarity. Analyses were carried out for all species and for subsets corresponding to each seed category. A total of 21,985 diaspores of 190 species were collected. Most seeds were small, shade-intolerant, and zoochoric, which corroborates other studies of fragmented forest landscapes and reflects the high disturbance levels in isolated forest remnants. Our data indicate that fragmentation processes such as habitat loss can alter species diversity and species composition by reducing habitat availability and increasing fragment isolation. We also found that large-seeded species are more affected by fragment isolation, possibly because their seed dispersers rarely cross non-forested areas between fragments, while zoochoric species are more strongly affected by fragment size and apparently more strongly associated with local edaphic conditions than with distance from seed sources.

  19. Dispersion of a layered electron gas with nearest neighbour-tunneling

    International Nuclear Information System (INIS)

    Miesenboeck, H.M.

    1988-09-01

    The dispersion of the first plasmon band is calculated within the Random Phase Approximation for a superlattice of two-dimensional electron-gases, mutually interacting, and with nearest neighbour hopping between the planes. It is further shown that the deviations of this dispersion from the one in systems with zero interplane motion are very small in commonly realized experimental situations and that they are expected to be observable only in samples with plane distances of 100A and less. (author). 15 refs, 3 figs, 1 tab

  20. Assessing the relative importance of dispersal in plant communities using an ecoinformatics approach

    NARCIS (Netherlands)

    Ozinga, W.A.; Hennekens, S.M.; Schaminée, J.H.J.; Bekker, R.M.; Prinzing, A.; Bonn, S.; Poschlod, P.; Tackenberg, O.; Thompson, K.; Bakker, J.P.; Groenendael, van J.M.

    2005-01-01

    Increased insight into the factors that determine the importance of dispersal limitation on species richness and species composition is of paramount importance for conservation and restoration ecology. One way to explore the importance of dispersal limitation is to use seed-sowing experiments, but

  1. Great cormorants reveal overlooked secondary dispersal of plants and invertebrates by piscivorous waterbirds

    NARCIS (Netherlands)

    van Leeuwen, C.H.A.; Lovas-Kiss, A.; Ovegård, M.; Green, Andy J.

    2017-01-01

    In wetland ecosystems, birds and fish are important dispersal vectors for plants and invertebrates, but the consequences of their interactions as vectors are unknown. Darwin suggested that piscivorous birds carry out secondary dispersal of seeds and invertebrates via predation on fish. We tested

  2. Microscale Insight into Microbial Seed Banks.

    Science.gov (United States)

    Locey, Kenneth J; Fisk, Melany C; Lennon, J T

    2016-01-01

    Microbial dormancy leads to the emergence of seed banks in environmental, engineered, and host-associated ecosystems. These seed banks act as reservoirs of diversity that allow microbes to persist under adverse conditions, including extreme limitation of resources. While microbial seed banks may be influenced by macroscale factors, such as the supply of resources, the importance of microscale encounters between organisms and resource particles is often overlooked. We hypothesized that dimensions of spatial, trophic, and resource complexity determine rates of encounter, which in turn, drive the abundance, productivity, and size of seed banks. We tested this using >10,000 stochastic individual based models (IBMs) that simulated energetic, physiological, and ecological processes across combinations of resource, spatial, and trophic complexity. These IBMs allowed realistic dynamics and the emergence of seed banks from ecological selection on random variation in species traits. Macroscale factors like the supply and concentration of resources had little effect on resource encounter rates. In contrast, encounter rates were strongly influenced by interactions between dispersal mode and spatial structure, and also by the recalcitrance of resources. In turn, encounter rates drove abundance, productivity, and seed bank dynamics. Time series revealed that energetically costly traits can lead to large seed banks and that recalcitrant resources can lead to greater stability through the formation of seed banks and the slow consumption of resources. Our findings suggest that microbial seed banks emerge from microscale dimensions of ecological complexity and their influence on resource limitation and energetic costs.

  3. Rapid and sensitive determination of major polyphenolic components in Euphoria longana Lam. seeds using matrix solid-phase dispersion extraction and UHPLC with hybrid linear ion trap triple quadrupole mass spectrometry.

    Science.gov (United States)

    Rathore, Atul S; Sathiyanarayanan, L; Deshpande, Shreekant; Mahadik, Kakasaheb R

    2016-11-01

    A rapid and sensitive method for the extraction and determination of four major polyphenolic components in Euphoria longana Lam. seeds is presented for the first time based on matrix solid-phase dispersion extraction followed by ultra high performance liquid chromatography with hybrid triple quadrupole linear ion trap mass spectrometry. Matrix solid-phase dispersion method was designed for the extraction of Euphoria longana seed constituents and compared with microwave-assisted extraction and ultrasonic-assisted extraction methods. An Ultra high performance liquid chromatography with hybrid triple quadrupole linear ion-trap mass spectrometry method was developed for quantitative analysis in multiple-reaction monitoring mode in negative electrospray ionization. The chromatographic separation was accomplished using an ACQUITY UPLC BEH C 18 (2.1 mm × 50 mm, 1.7 μm) column with gradient elution of 0.1% aqueous formic acid and 0.1% formic acid in acetonitrile. The developed method was validated with acceptable linearity (r 2 > 0.999), precision (RSD ≤ 2.22%) and recovery (RSD ≤ 2.35%). The results indicated that matrix solid-phase dispersion produced comparable extraction efficiency compared with other methods nevertheless was more convenient and time-saving with reduced requirements on sample and solvent volumes. The proposed method is rapid and sensitive in providing a promising alternative for extraction and comprehensive determination of active components for quality control of Euphoria longana products. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Generation of a few femtoseconds pulses in seeded FELs using a seed laser with small transverse size

    Energy Technology Data Exchange (ETDEWEB)

    Li, Heting, E-mail: liheting@ustc.edu.cn; Jia, Qika

    2016-09-11

    We propose a simple method to generate a few femtosecond pulses in seeded FELs. We use a longitudinal energy-chirped electron beam passing through a dogleg where transverse dispersion will generate a horizontal energy chirp, then in the modulator, a seed laser with narrow beam radius will only modulate the center portion of the electron beam and then short pulses at high harmonics will be generated in the radiator. Using a representative realistic set of parameters, we show that 30 nm XUV pulse based on the HGHG scheme and 9 nm soft x-ray pulse based on the EEHG scheme with duration of about 8 fs (FWHM) and peak power of GW level can be generated from a 180 nm UV seed laser with beam waist of 75 μm. This new scheme can provide an optional operation mode for the existing seeded FEL facilities to meet the requirement of short-pulse FEL.

  5. Slipping vs sticking: water-dependent adhesive and frictional properties of Linum usitatissimum L. seed mucilaginous envelope and its biological significance.

    Science.gov (United States)

    Kreitschitz, Agnieszka; Kovalev, Alexander; Gorb, Stanislav N

    2015-04-01

    Flax seeds produce mucilage after wetting. The mucilage due to its ability to absorb and maintain water is responsible for specific surface properties which are essential for seed dispersal in different ways. In the present paper, we asked how the hydration level affects the adhesive and frictional properties of the mucilage and which role does the mucilage play in seed dispersal? We have experimentally quantified: (1) desiccation dynamics of seeds with a mucilage envelope, (2) desiccation-time dependence of their friction coefficient, and (3) desiccation-time dependence of their pull-off forces on a smooth glass substrate. Freshly-hydrated seeds had an extremely low friction coefficient, which rapidly increased with an increasing desiccation time. Pull-off force just after hydration was rather low, then increased with an increasing water loss. Adhesion and friction experiments show that there is a clear maximum in the force values at certain hydration states of the mucilage. Different hydration levels of the mucilage can be employed in various dispersal mechanisms. Fully hydrated mucilage with its low viscosity gives optimal sliding conditions for endozoochory, whereas water loss provides conditions for the epizoochory. We suggest that the hydration level of the mucilage envelope can determine the potential mode of flax seed dispersal. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  6. Scientific designs of pine seeds and pine cones for species conservation

    Science.gov (United States)

    Song, Kahye; Yeom, Eunseop; Kim, Hyejeong; Lee, Sang Joon

    2015-11-01

    Reproduction and propagation of species are the most important missions of every living organism. For effective species propagation, pine cones fold their scales under wet condition to prevent seeds from short-distance dispersal. They open and release their embedded seeds on dry and windy days. In this study, the micro-/macro-scale structural characteristics of pine cones and pine seeds are studied using various imaging modalities. Since the scales of pine cones consist of dead cells, the folding motion is deeply related to structural changes. The scales of pine cones consist of three layers. Among them, bract scales are only involved in collecting water. This makes pine cones reduce the amount of water and minimize the time spent on structural changes. These systems also involve in drying and recovery of pine cones. In addition, pine cones and pine seeds have advantageous structures for long-distance dispersal and response to natural disaster. Owing to these structural features, pine seeds can be released safely and efficiently, and these types of structural advantages could be mimicked for practical applications. This research was financially supported by the Creative Research Initiative of the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of Korea (Contract grant number: 2008-0061991).

  7. Seed size and nutrient content variation for twenty-one invasive and native California and Oregon taxa of the tribe Cynareae (Asteraceae)

    Science.gov (United States)

    Seed characteristics are important for seed dispersal, seedling growth, and seedling survival, but there is little information on seed characteristics for several taxa of the tribe Cynareae (Family: Asteraceae). We determined seed characteristics and their variation from natural populations of twen...

  8. Seed production and dispersal of sulfur cinquefoil in northeast Oregon

    Science.gov (United States)

    Kathleen A. Dwire; Catherine G. Parks; Michael L. McInnis; Bridgett J. Naylor

    2006-01-01

    Sulfur cinquefoil (family Rosaceae) is an invasive, herbaceous perennial, native to Eurasia. It has wide ecological amplitude and has become established throughout North America in numerous habitat types. Sulfur cinquefoil reproduces only by seed (achenes); however, little is known about its regenerative strategy or reproductive biology. To improve understanding of the...

  9. Plant species dispersed by Galapagos tortoises surf the wave of habitat suitability under anthropogenic climate change.

    Science.gov (United States)

    Ellis-Soto, Diego; Blake, Stephen; Soultan, Alaaeldin; Guézou, Anne; Cabrera, Fredy; Lötters, Stefan

    2017-01-01

    Native biodiversity on the Galapagos Archipelago is severely threatened by invasive alien species. On Santa Cruz Island, the abundance of introduced plant species is low in the arid lowlands of the Galapagos National Park, but increases with elevation into unprotected humid highlands. Two common alien plant species, guava (Psidium guajava) and passion fruit (Passiflora edulis) occur at higher elevations yet their seeds are dispersed into the lowlands by migrating Galapagos tortoises (Chelonoidis spp.). Tortoises transport large quantities of seeds over long distances into environments in which they have little or no chance of germination and survival under current climate conditions. However, climate change is projected to modify environmental conditions on Galapagos with unknown consequences for the distribution of native and introduced biodiversity. We quantified seed dispersal of guava and passion fruit in tortoise dung piles and the distribution of adult plants along two elevation gradients on Santa Cruz to assess current levels of 'wasted' seed dispersal. We computed species distribution models for both taxa under current and predicted future climate conditions. Assuming that tortoise migratory behaviour continues, current levels of "wasted" seed dispersal in lowlands were projected to decline dramatically in the future for guava but not for passion fruit. Tortoises will facilitate rapid range expansion for guava into lowland areas within the Galapagos National Park where this species is currently absent. Coupled with putative reduction in arid habitat for native species caused by climate change, tortoise driven guava invasion will pose a serious threat to local plant communities.

  10. Plant species dispersed by Galapagos tortoises surf the wave of habitat suitability under anthropogenic climate change.

    Directory of Open Access Journals (Sweden)

    Diego Ellis-Soto

    Full Text Available Native biodiversity on the Galapagos Archipelago is severely threatened by invasive alien species. On Santa Cruz Island, the abundance of introduced plant species is low in the arid lowlands of the Galapagos National Park, but increases with elevation into unprotected humid highlands. Two common alien plant species, guava (Psidium guajava and passion fruit (Passiflora edulis occur at higher elevations yet their seeds are dispersed into the lowlands by migrating Galapagos tortoises (Chelonoidis spp.. Tortoises transport large quantities of seeds over long distances into environments in which they have little or no chance of germination and survival under current climate conditions. However, climate change is projected to modify environmental conditions on Galapagos with unknown consequences for the distribution of native and introduced biodiversity. We quantified seed dispersal of guava and passion fruit in tortoise dung piles and the distribution of adult plants along two elevation gradients on Santa Cruz to assess current levels of 'wasted' seed dispersal. We computed species distribution models for both taxa under current and predicted future climate conditions. Assuming that tortoise migratory behaviour continues, current levels of "wasted" seed dispersal in lowlands were projected to decline dramatically in the future for guava but not for passion fruit. Tortoises will facilitate rapid range expansion for guava into lowland areas within the Galapagos National Park where this species is currently absent. Coupled with putative reduction in arid habitat for native species caused by climate change, tortoise driven guava invasion will pose a serious threat to local plant communities.

  11. Adaptation of flower and fruit colours to multiple, distinct mutualists.

    Science.gov (United States)

    Renoult, Julien P; Valido, Alfredo; Jordano, Pedro; Schaefer, H Martin

    2014-01-01

    Communication in plant-animal mutualisms frequently involves multiple perceivers. A fundamental uncertainty is whether and how species adapt to communicate with groups of mutualists having distinct sensory abilities. We quantified the colour conspicuousness of flowers and fruits originating from one European and two South American plant communities, using visual models of pollinators (bee and fly) and seed dispersers (bird, primate and marten). We show that flowers are more conspicuous than fruits to pollinators, and the reverse to seed dispersers. In addition, flowers are more conspicuous to pollinators than to seed dispersers and the reverse for fruits. Thus, despite marked differences in the visual systems of mutualists, flower and fruit colours have evolved to attract multiple, distinct mutualists but not unintended perceivers. We show that this adaptation is facilitated by a limited correlation between flower and fruit colours, and by the fact that colour signals as coded at the photoreceptor level are more similar within than between functional groups (pollinators and seed dispersers). Overall, these results provide the first quantitative demonstration that flower and fruit colours are adaptations allowing plants to communicate simultaneously with distinct groups of mutualists. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  12. Plant seeds as sources of potential industrial chemicals, pharmaceuticals, and pest control agents.

    Science.gov (United States)

    Powell, Richard G

    2009-03-27

    Investigations of natural products isolated from seeds have resulted in a remarkable variety of compounds having unusual structures. Seeds of many plant species contain uncommon fatty acids and lipids, some of which have found uses in the cosmetic industry or as renewable (non-petroleum based) industrial raw materials. In addition to proteins and energy storage substances such as carbohydrates and lipids, seeds generally contain, or have the ability to produce, protective compounds that are active as plant growth regulators, fungicides, insecticides, and repellents of herbivores; seeds occasionally contain compounds that are toxic to most other organisms. These compounds may also be present in other plant parts, but often are found at higher concentrations in seeds. Other compounds of interest have been associated with plant-endophyte interactions that are of mutual benefit to both organisms. Tests of seed extracts for cytotoxic and antitumor activity, toxicity to insects, and relationships to several animal disease syndromes have been revealing. Examples of compounds isolated from plant seeds that have served as lead compounds for additional research, or that continue to be of interest to researchers in multiple areas, are reviewed.

  13. Pulse-front tilt caused by the use of a grating monochromator and self-seeding of soft X-ray FELs

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2012-03-15

    Self-seeding is a promising approach to significantly narrow the SASE bandwidth of XFELs to produce nearly transform-limited pulses. The development of such schemes in the soft X-ray wavelength range necessarily involves gratings as dispersive elements. These introduce, in general, a pulse-front tilt, which is directly proportional to the angular dispersion. Pulse-front tilt may easily lead to a seed signal decrease by a factor two or more. Suggestions on how to minimize the pulse-front tilt effect in the self-seeding setup are given. (orig.)

  14. Pulse-front tilt caused by the use of a grating monochromator and self-seeding of soft X-ray FELs

    International Nuclear Information System (INIS)

    Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

    2012-03-01

    Self-seeding is a promising approach to significantly narrow the SASE bandwidth of XFELs to produce nearly transform-limited pulses. The development of such schemes in the soft X-ray wavelength range necessarily involves gratings as dispersive elements. These introduce, in general, a pulse-front tilt, which is directly proportional to the angular dispersion. Pulse-front tilt may easily lead to a seed signal decrease by a factor two or more. Suggestions on how to minimize the pulse-front tilt effect in the self-seeding setup are given. (orig.)

  15. [Soil seed bank formation during early revegetation of areas affected by mining in a tropical rain forest of Chocó, Colombia].

    Science.gov (United States)

    Valois-Cuesta, Hamleth; Martínez-Ruiz, Carolina; Urrutia-Rivas, Yorley

    2017-03-01

    Mining is one of the main economic activities in many tropical regions and is the cause of devastation of large areas of natural tropical forests. The knowledge of the regenerative potential of mining disturbed areas provides valuable information for their ecological restoration. The aim of this study was to evaluate the effect of age of abandonment of mines and their distance from the adjacent forest, on the formation of soil seed bank in abandoned mines in the San Juan, Chocó, Colombia. To do this, we determined the abundance and species composition of the soil seed bank, and the dynamics of seed rain in mines of different cessation period of mining activity (6 and 15 years), and at different distances from the adjacent forest matrix (50 and 100 m). Seed rain was composed by five species of plants with anemocorous dispersion, and was more abundant in the mine of 6 years than in the mine of 15 years. There were no significant differences in the number of seeds collected at 50 m and 100 m from the adjacent forest. The soil seed bank was represented by eight species: two with anemocorous dispersion (common among the seed rain species) and the rest with zoochorous dispersion. The abundance of seeds in the soil did not vary with the age of the mine, but was higher at close distances to the forest edge than far away. During the early revegetation, the formation of the soil seed bank in the mines seems to be related to their proximity to other disturbed areas, rather than their proximity to the adjacent forest or the cessation activity period of mines. Therefore, the establishment of artificial perches or the maintenance of isolated trees in the abandoned mines could favour the arrival of bird-dispersed seeds at mines. However, since the soil seed bank can be significantly affected by the high rainfall in the study area, more studies are needed to evaluate management actions to encourage soil seed bank formation in mines of high-rainfall environments in the Choc

  16. Potential external contamination of pneumatic seed drills during sowing of dressed maize seeds.

    Science.gov (United States)

    Manzone, Marco; Balsari, Paolo; Marucco, Paolo; Tamagnone, Mario

    2016-07-01

    The use of pneumatic drills in maize cultivation causes dispersion in the atmosphere of some harmful substances normally used for dressing maize seeds. Some of the dust particles may be deposited on the machine's body, becoming dangerous for the environment and for operators. The aim of the present study was to analyse the amount of dust deposited on the frame of drills during maize sowing operations. Tests were performed with different drills and in different operating conditions. Data analysis showed that a significant amount (up to 30%) of the tracer can be deposited on the drill body. When wind was not present, higher quantities of tracer were collected and the forward speed did not influence significantly the tracer deposit on the seed drills. The use of different devices designed to prevent dust dispersion was able to limit up to 95% but was not able to eliminate the external contamination of the drill. The particles present on drills could become a problem for the operator during the filling of the drill. Additionally, the environment can be contaminated if pesticide remains on the drill, generating point-source pollution when the drill is parked outside. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

  17. On-the-fly green generation and dispersion of AgI nanoparticles for cloud seeding nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Xiuli; Zhou, Wenbo; Wang, Xizheng; Wu, Tao; Delisio, Jeffery B.; Zachariah, Michael R., E-mail: mrz@umd.edu [University of Maryland, Department of Chemical and Biomolecular Engineering (United States)

    2016-07-15

    This study reports on an on-the-fly green synthesis/dispersion of silver iodide (AgI) nanoparticles from the combustion of AgIO{sub 3}/carbon black (CB)/nitrocellulose (NC) composites, which could be used as a candidate for a cloud-seeding pyrotechnic. Films were formed by direct electrospray deposition of a mixture of synthesized silver iodate with CB and NC. The decomposition pathways of AgIO{sub 3}/CB and AgIO{sub 3}/CB/NC were evaluated by temperature jump time of flight mass spectrometry (T-jump TOFMS) and XRD, showing that AgI particles and CO{sub 2} are released from the reaction between AgIO{sub 3} and CB without other toxic residuals. The flame propagation velocity of AgIO{sub 3}/CB/NC films increases with the increasing of particle mass loading of AgIO{sub 3} and CB and peaks at 40 wt%, which is much higher than that of an AgI/AP/NC film. The mean diameter of the resultant AgI nanoparticles is from 51 to 97 nm. The mass loading of AgIO{sub 3} and CB was found to play a major role in size control of the AgI nanoparticles.

  18. Does retained-seed priming drive the evolution of serotiny in drylands? An assessment using the cactus Mammillaria hernandezii.

    Science.gov (United States)

    Santini, Bianca A; Martorell, Carlos

    2013-02-01

    Serotinous plants retain their seeds for a long time. In deserts, retained seeds undergo hydration-dehydration cycles and thus may become primed. Priming enhances germination and seedling vigor. We test the hypothesis that serotiny evolves because it provides a site protected from predators in which seeds can become primed. Rainfall-cued dispersal of primed seeds may enhance this effect. We tested this hypothesis with Mammillaria hernandezii through protein-content analyses; field and laboratory germination experiments with primed, unprimed, and retained seeds; and fitness estimations from demographic models. Hydration-dehydration cycles induced priming, enhancing germination. Artificial priming and retention in the parent plant for 1 yr induced similar changes in seed protein patterns, suggesting that priming occurs naturally while seeds are retained. Under field conditions, germination of seeds retained for 1 yr more than doubled that of seeds of the same cohort that were not primed or that remained buried for 1 yr. The first seeds to germinate died rapidly. Serotinous plants whose seeds underwent priming had higher fitness than those whose seeds were in the soil seed bank or that did not experience priming. Priming in soil seed banks may be costly because of high predation, so seed protection during priming is sufficient to promote the evolution of serotiny. Bet hedging contributes to this process. Rapid germination of primed seeds that respond to brief rainfall events is disadvantageous because such rainfall is insufficient for seedling survival. Serotinous species counteract this cost by cueing dispersal with heavy precipitation.

  19. Fate of native and introduced seeds consumed by captive white-lipped and collared peccaries (Tayassu pecari, Link 1795 and Pecari tajacu, Linnaeus 1758 in the Atlantic rainforest, Brazil

    Directory of Open Access Journals (Sweden)

    L. Lazure

    Full Text Available We studied the role of white-lipped and collared peccaries (Tayassu pecari and Pecari tajacu as seed predators and dispersers in the Atlantic rainforest of Brazil. The Atlantic rainforest ecosystem is highly threatened and has experienced dramatic declines in its populations of large mammals. Local extinctions can disrupt essential plant-animal interactions such as seed dispersion and seed predation. We tracked seeds from time of consumption to germination to assess the direct impact peccaries have on seed survival. We offered fruits of 20 species found in the Atlantic rainforest to the peccaries. Seeds were categorised as intact, scarified, ingested or defecated, and germination tests were performed. The overall impact by both peccary species was similar. Seeds were sometime scarified by mastication, always with fatal consequences. Most seeds that were consumed were destroyed during ingestion and digestion. Only small seeds (<10 mm were found in the feces and germination tests suggest a positive effect from the passage through the guts. Peccaries clearly have a double role as both seed predators and as small seeds dispersers, which is a specialised role within the granivore/frugivore community of the Atlantic rainforest.

  20. Does Ferocactus wislizeni (Cactaceae) have a between-year seed bank?

    Science.gov (United States)

    Bowers, Janice E.

    2000-01-01

    Field and laboratory experiments at Tumamoc Hill, Tucson, Arizona, U.S.A., demonstrated that Ferocactus wislizeni, a common perennial cactus in the northern Sonoran Desert, has a between-year seed bank. In laboratory studies, F. wislizeni seeds lost dormancy during storage at room temperature and had a light requirement for germination. Field experiments suggested that as much as 2% of the annual seed crop might escape post-dispersal predation even when unprotected; where suitable safe sites exist, a higher percentage might escape. Germination of seed recovered monthly from above- and below-ground components of an artificial seed bank showed that seeds can survive at least 18 months in and on the soil. Seed banks enable F. wislizeni to take advantage of favorable rains and temperatures throughout the growing season, thus increasing the number of opportunities for germination. Moreover, seed banks enable F. wislizeni to respond hugely when the climate seems especially favorable, thus producing the large cohorts necessary to compensate for high seedling mortality. (C) 2000 Academic Press.

  1. Differences in seed rain composition in small and large fragments in the northeast Brazilian Atlantic Forest.

    Science.gov (United States)

    Knörr, U C; Gottsberger, G

    2012-09-01

    Tropical forests are seriously threatened by fragmentation and habitat loss. The impact of fragment size and forest configuration on the composition of seed rain is insufficiently studied. For the present study, seed rain composition of small and large forest fragments (8-388 ha) was assessed in order to identify variations in seed abundance, species richness, seed size and dispersal mode. Seed rain was documented during a 1-year period in three large and four small Atlantic Forest fragments that are isolated by a sugarcane matrix. Total seed rain included 20,518 seeds of 149 species of trees, shrubs, palms, lianas and herbs. Most species and seeds were animal-dispersed. A significant difference in the proportion of seeds and species within different categories of seed size was found between small and large fragments. Small fragments received significantly more very small-sized seeds (1.5 cm) that were generally very rare, with only one species in small and eight in large fragments. We found a negative correlation between the inflow of small-sized seeds and the percentage of forest cover. Species richness was lower in small than in large fragments, but the difference was not very pronounced. Given our results, we propose changing plant species pools through logging, tree mortality and a high inflow of pioneer species and lianas, especially in small forest fragments and areas with low forest cover. Connecting forest fragments through corridors and reforestation with local large-seeded tree species may facilitate the maintenance of species diversity. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

  2. Semantic Representation of Mutual-Consent Divorce

    Directory of Open Access Journals (Sweden)

    مهری سادات موسوی

    2016-09-01

    Full Text Available This article discussed mutual-consent divorce in the context of thoughts and attitude of female applicants of this type of divorce with an inductive qualitative and ethnographic method. Based on the qualitative purposive sampling, 30 women of those who had referred for divorce to family court of Karaj, were selected and deeply interviewed. The results obtained in six major categories as follows: Rethinking the role of men as families’ breadwinners, inappropriate sexual relationships, emotional conflicts, cultural- social dissensions, normative pressures of family and relatives, and personality and behavioral disorders. The core-oriented category of this study is "Women's attitude towards mutual-consent divorce" that includes other major categories and can semantically alter and redirect women’s opinion about mutual-consent divorce. According to the results, the term of mutual-consent is thought-provoking in this type of divorce; because considering the situations which were leaded to mutual-consent divorce and quantifying them revealed that nearly 32% of mutual-consent divorces were not mutual in fact; since, these women accepted divorce with desperation, coercion and threat.

  3. Tree seed rain and seed removal, but not the seed bank, impede forest recovery in bracken (Pteridium aquilinum (L.) Kuhn)-dominated clearings in the African highlands.

    Science.gov (United States)

    Ssali, Fredrick; Moe, Stein R; Sheil, Douglas

    2018-04-01

    Considerable areas dominated by bracken Pteridium aquilinum (L.) Kuhn occur worldwide and are associated with arrested forest recovery. How forest recovery is impeded in these areas remains poorly understood, especially in the African highlands. The component processes that can lead to recruitment limitation-including low seed arrival, availability and persistence-are important determinants of plant communities and offer a potential explanation for bracken persistence. We investigated key processes that can contribute to recruitment limitation in bracken-dominated clearings in the Bwindi Impenetrable National Park, Uganda. We examined if differences in seed rain (dispersal limitation), soil seed bank, or seed removal (seed viability and persistence) can, individually or in combination, explain the differences in tree regeneration found between bracken-dominated areas and the neighboring forest. These processes were assessed along ten 50-m transects crossing the forest-bracken boundary. When compared to the neighboring forest, bracken clearings had fewer seedlings (bracken 11,557 ± 5482 vs. forest 34,515 ± 6066 seedlings/ha), lower seed rain (949 ± 582 vs. 1605 ± 335 tree seeds m -2  year -1 ), comparable but sparse soil seed bank (304 ± 236 vs. 264 ± 99 viable tree seeds/m 2 ), higher seed removal (70.1% ± 2.4% vs. 40.6% ± 2.4% over a 3-day interval), and markedly higher rodent densities (25.7 ± 5.4 vs. 5.0 ± 1.6 rodents per 100 trapping sessions). Camera traps revealed that rodents were the dominant animals visiting the seeds in our seed removal study. Synthesis : Recruitment limitation contributes to both the slow recovery of forest in bracken-dominated areas, and to the composition of the tree species that occur. Low seed arrival and low persistence of unburied seeds can both explain the reduced density of seedlings found in bracken versus neighboring forest. Seed removal, likely due to rodents, in particular appears sufficient to

  4. Harmonization versus Mutual Recognition

    DEFF Research Database (Denmark)

    Jørgensen, Jan Guldager; Schröder, Philipp

    The present paper examines trade liberalization driven by the coordination of product standards. For oligopolistic firms situated in separate markets that are initially sheltered by national standards, mutual recognition of standards implies entry and reduced profits at home paired with the oppor......The present paper examines trade liberalization driven by the coordination of product standards. For oligopolistic firms situated in separate markets that are initially sheltered by national standards, mutual recognition of standards implies entry and reduced profits at home paired...... countries and three firms, where firms first lobby for the policy coordination regime (harmonization versus mutual recognition), and subsequently, in case of harmonization, the global standard is auctioned among the firms. We discuss welfare effects and conclude with policy implications. In particular......, harmonized standards may fail to harvest the full pro-competitive effects from trade liberalization compared to mutual recognition; moreover, the issue is most pronounced in markets featuring price competition....

  5. Maximum mutual information regularized classification

    KAUST Repository

    Wang, Jim Jing-Yan

    2014-09-07

    In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.

  6. Maximum mutual information regularized classification

    KAUST Repository

    Wang, Jim Jing-Yan; Wang, Yi; Zhao, Shiguang; Gao, Xin

    2014-01-01

    In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.

  7. Two thrush species as dispersers of Miconia prasina (Sw. DC. (Melastomataceae: an experimental approach

    Directory of Open Access Journals (Sweden)

    MAS. Alves

    Full Text Available We carried out a seed germination experiment using two thrush species in captivity. We compared the number of germinated seeds and germination time of control seeds (manually removed from fruits and ingested seeds of Miconia prasina by two bird species, Turdus albicollis and T. amaurochalinus, and also compared retention times of seeds by both thrush species. Control seeds germinated more frequently than those ingested for one species, T. albicollis. The germination time of ingested seeds by T. amaurochalinus was similar to the control seeds but seeds ingested by T. albicollis took longer to germinate than the controls. Both thrush species had a similar seed defecation pattern. The cumulative number of defecated seeds increased by 2 hours after fruit ingestion. At the end of the first 30 minutes both species had already defecated approximately 50% of the seeds ingested Our results suggest that both species could act as disperser agents of M. prasina.

  8. The Analysis of Mutual Fund Performance: Evidence from U.S. Equity Mutual Funds

    NARCIS (Netherlands)

    D.P. Budiono (Diana)

    2010-01-01

    textabstractWe study the mutual fund performance for about 45 years. There are several key points that we can withdraw from this dissertation. First, to study the persistence of mutual fund performance, it is important to consider time-varying exposures because when they are ignored, the persistence

  9. Lack of divergence in seed ecology of two Amphicarpaea (Fabaceae) species disjunct between eastern Asia and eastern North America.

    Science.gov (United States)

    Zhang, Keliang; Baskin, Jerry M; Baskin, Carol C; Yang, Xuejun; Huang, Zhenying

    2015-06-01

    Many congeneric species are disjunct between eastern Asia and eastern North America. No previous study has compared the seed biology of closely related disjunct taxa of legumes or of a diaspore-heteromorphic species. Our objective was to compare seed dormancy in two such sister species in the genus Amphicarpaea (Fabaceae). We investigated the ecology and ecophysiology of aerial and subterranean seeds of the amphicarpic species Amphicarpaea edgeworthii from China and compared the results to those published for its sister species A. bracteata from eastern North America. The seed coat of aerial seeds of A. edgeworthii is well developed, whereas the seed coat of subterranean seeds is not. Aerial seeds have combinational dormancy (physical dormancy [PY] + physiological dormancy [PD]) broken by scarification followed by cold stratification or by after-ripening and scarification; whereas subterranean seeds have PD broken by cold stratification. Aerial seeds formed a persistent soil seed bank, and subterranean seeds a transient soil seed bank. Aerial seeds of A. bracteata also have PY+PD and subterranean seeds PD. Subterranean seeds of both species are desiccation intolerant. Dormancy in neither aerial nor subterranean seeds of both species has diverged over geological time. Compared to subterranean seeds, aerial seeds of both species dispersed over longer distances. Seed dispersal ability and degree of dormancy of neither species fits the high-risk/low-risk (H-H/L-L) strategy found in many diaspore-dimorphic species. Rather, both species have an H-L/L-H strategy for these two life history traits. © 2015 Botanical Society of America, Inc.

  10. Generalist dispersers promote germination of an alien fleshy-fruited tree invading natural grasslands.

    Directory of Open Access Journals (Sweden)

    Martín Raúl Amodeo

    Full Text Available Plants with animal-dispersed fruits seem to overcome the barriers that limit their spread into new habitats more easily than other invasive plants and, at the same time, they pose special difficulties for containment, control or eradication. The effects of animals on plant propagules can be very diverse, with positive, neutral or negative consequences for germination and recruitment. Moreover, the environmental conditions where the seeds are deposited and where the post-dispersal processes take place can be crucial for their fate. Prunus mahaleb is a fleshy-fruited tree invading natural grasslands in the Argentine Pampas. In this study, we analyzed the importance of pulp removal, endocarp scarification and the effects of vectors on its germination response, by means of germination experiments both in the laboratory and under semi-natural conditions. Our laboratory results demonstrated that endocarp scarification enhances germination and suggests that vestiges of pulp on the stones have inhibitory effects. Frugivores exert a variety of effects on germination responses and this variation can be explained by their differing influence on pulp removal and endocarp scarification. Most frugivores produced a positive effect on germination under laboratory conditions, in comparison to intact fruits and hand-peeled stones. We observed different degrees of pulp removal from the surface of the stones by the dispersers which was directly correlated to the germination response. On the other hand, all the treatments showed high germination responses under semi-natural conditions suggesting that post-dispersal processes, like seed burial, and the exposure to natural conditions might exert a positive effect on germination response, attenuating the plant's dependence on the dispersers' gut treatment. Our results highlight the need to consider the whole seed dispersal process and the value of combining laboratory and field tests.

  11. Mutuality in the provision of Scottish healthcare.

    Science.gov (United States)

    Howieson, Brian

    2015-11-01

    The backdrop to this article is provided by the Better Health, Better Care Action Plan (Scottish Government, 2007), Section 1 of which is entitled 'Towards a Mutual NHS'. According to Better Health, Better Care (Scottish Government, 2007: 5): 'Mutual organisations are designed to serve their members. They are designed to gather people around a common sense of purpose. They are designed to bring the organisation together in what people often call "co-production."' The aim of this article is to précis the current knowledge of mutuality in the provision of Scottish healthcare. In detail, it will: introduce the 'mutual' organisation; offer a historical perspective of mutuality; suggest why healthcare mutuality is important; and briefly, detail the differences in mutual health-care policy in England and Scotland. It is hoped that this analysis will help researchers and practitioners alike appreciate further the philosophy of mutuality in the provision of Scottish healthcare. © The Author(s) 2015.

  12. Interim evaluation report of the mutually operable database systems by different computers; Denshi keisanki sogo un'yo database system chukan hyoka hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1989-03-01

    This is the interim report on evaluation of the mutually operable database systems by different computers. The techniques for these systems fall into four categories of those related to (1) dispersed data systems, (2) multimedia, (3) high reliability, and (4) elementary techniques for mutually operable network systems. The techniques for the category (1) include those for vertically dispersed databases, database systems for multiple addresses in a wide area, and open type combined database systems, which have been in progress generally as planned. Those for the category (2) include the techniques for color document inputting and information retrieval, meaning compiling, understanding highly overlapping data, and controlling data centered by drawings, which have been in progress generally as planned. Those for the category (3) include the techniques for improving resistance of the networks to obstruction, and security of the data in the networks, which have been in progress generally as planned. Those for the category (4) include the techniques for rule processing for development of protocols, protocols for mutually connecting the systems, and high-speed, high-function networks, which have been in progress generally as planned. It is expected that the original objectives are finally achieved, because the development programs for these categories have been in progress generally as planned. (NEDO)

  13. O lambari Astyanax altiparanae (Characidae pode ser um dispersor de sementes? - DOI: 10.4025/actascibiolsci.v25i2.2045 Can lambari, Astyanax altiparanae (Characidae, be a seed disperser? - DOI: 10.4025/actascibiolsci.v25i2.2045

    Directory of Open Access Journals (Sweden)

    Leandro Muller Gomiero

    2003-04-01

    Full Text Available Este trabalho caracterizou a alimentação natural de Astyanax altiparanae na sub-bacia do rio Corumbataí e bacia do rio Jacaré-pepira, com enfoque principal na ingestão de sementes de Croton urucurana. Os itens alimentares de Astyanax altiparanae, em ordem decrescente de Grau de Preferência Alimentar (GPA, foram: insetos alóctones, restos de insetos, material vegetal alóctone, sementes de Croton urucurana, insetos autóctones, sedimentos, material vegetal autóctone, escamas, ovócitos e aracnídeos. Sementes de Croton urucurana ocorreram no verão, época de cheia dos rios. Sugere-se que Astyanax altiparanae seja um dispersor secundário das sementes de Croton urucurana, sendo que a intensidade e a efetividade dessa dispersão devem, ainda, ser investigadasThis work characterized the feeding of Astyanax altiparanae in the sub-basin of Corumbataí river and in the basin of Jacaré-pepira river with a focus on the ingestion of Croton urucurana seeds. The food items of Astyanax altiparanae were, in decreasing APD (Alimentary Preference Degree order: allochthonous insects, allochthonous plant material, Croton urucurana seeds, autochthonous insects, sediments, autochthonous plant material, scales, oocytes and arachnidans. Croton urucurana seeds occurred during the summer, in the flood period. Lambari, Astyanax altiparanae, could be a secondary disperser of Croton urucurana seeds, however, the intensity and effectiveness of this dispersion may be still investigated

  14. Implementation of mutual exclusion in VHDL

    NARCIS (Netherlands)

    Boersma, M.V.; Benders, L.P.M.; Stevens, M.P.J.; Wilsey, P.A.; Rhodes, D.

    1994-01-01

    In VHDL it is difficult to implement mutual exclusion at an abstract level since atomic actions are required. A local status model and an arbiter model are presented to achieve mutual exclusion in VHDL. Shared data, protected by a mutual exclusion mechanism, cannot be modelled as a simple, resolved

  15. An indirect dispersal pathway for spotted knapweed seeds via deer mice and great-horned owls

    Science.gov (United States)

    Dean E. Pearson; Yvette K. Ortega

    2001-01-01

    Spotted Knapweed (Centaurea maculosa) seeds were found in the pellets of Great Horned Owls (Bubo virginianus). That apparently resulted from owls preying upon Deer Mice (Peromyscus maniculatus) which had incidentally consumed knapweed seeds while foraging for the larvae of biological control agents within...

  16. Epoxy resins used to seal brachytherapy seed

    International Nuclear Information System (INIS)

    Ferreira, Natalia Carolina Camargos; Ferraz, Wilmar Barbosa; Reis, Sergio Carneiro dos; Santos, Ana Maria Matildes dos

    2013-01-01

    Prostate cancer treatment with brachytherapy is recommended for patients with cancer at an early stage. In this treatment, small radioactive seeds are implanted directly in the prostate gland. These seeds are composed at least of one radionuclide carrier and an X-ray marker enclosed within a metallic tube usually sealed by laser process. This process is expensive and, furthermore, it can provoke a partial volatilization of the radionuclide and change the isotropy in dose distribution around the seed. In this paper, we present a new sealing process using epoxy resin. Three kinds of resins were utilized and characterized by scanning electron microscopy (SEM), energy dispersive X ray (EDS) and by differential scanning calorimetry (DSC) after immersion in simulated body fluid (SBF) and in sodium iodine solution (NaI). The sealing process showed excellent potential to replace the sealing laser usually employed. (author)

  17. Importance of earthworm-seed interactions for the composition and structure of plant communities: A review

    Science.gov (United States)

    Forey, Estelle; Barot, Sébastien; Decaëns, Thibaud; Langlois, Estelle; Laossi, Kam-Rigne; Margerie, Pierre; Scheu, Stefan; Eisenhauer, Nico

    2011-11-01

    Soil seed bank composition and dynamics are crucial elements for the understanding of plant population and community ecology. Earthworms are increasingly recognized as important dispersers and predators of seeds. Through direct and indirect effects they influence either positively or negatively the establishment and survival of seeds and seedlings. Seedling establishment is affected by a variety of earthworm-mediated mechanisms, such as selective seed ingestion and digestion, acceleration or deceleration of germination, and seed transport. Earthworm casts deposited on the soil surface and the entrance of earthworm burrows often contain viable seeds and constitute important regeneration niches for plant seedlings and therefore likely favour specific seed traits. However, the role of earthworms as seed dispersers, mediators of seed bank dynamics and seed predators has not been considered in concert. The overall effect of earthworms on plant communities remains little understood. Most knowledge is based on laboratory studies on temperate species and future work has to explore the biological significance of earthworm-seed interactions under more natural conditions. In this review we summarize the current knowledge on earthworm-seed interactions and discuss factors determining these interactions. We highlight that this interaction may be an underappreciated, yet major driving force for the dynamics of soil seed banks and plant communities which most likely have experienced co-evolutionary processes. Despite the experimental bias, we hypothesize that the knowledge gathered in the present review is of crucial relevance for restoration and conservation ecology. For instance, as earthworms emerge as successful and ubiquitous invaders in various ecosystems, the summarized information might serve as a basis for realistic estimations and modelling of consequences on native plant communities. We depict promising directions of future research and point to the need to consider

  18. Rating mutual funds

    DEFF Research Database (Denmark)

    Bechmann, Ken L.; Rangvid, Jesper

    2007-01-01

    We develop a new rating of mutual funds: the atpRating. The atpRating assigns crowns to each individual mutual fund based upon the costs an investor pays when investing in the fund in relation to what it would cost to invest in the fund's peers. Within each investment category, the rating assigns...... the return of a fund in a certain year generally contains only little information about the future return that the fund will generate. Finally, we have information on the investments in different mutual funds made by a small subgroup of investors known to have been exposed to both the atp...... five crowns to funds with the lowest costs and one crown to funds with the highest costs. We investigate the ability of the atpRating to predict the future performance of a fund. We find that an investor who has invested in the funds with the lowest costs within an investment category would have...

  19. Rating Mutual Funds

    DEFF Research Database (Denmark)

    Bechmann, Ken L.; Rangvid, Jesper

    We develop a new rating of mutual funds: the atpRating. The atpRating assigns crowns to each individual mutual fund based upon the costs an investor pays when investing in the fund in relation to what it would cost to invest in the fund’s peers. Within each investment category, the rating assigns......, whereas the return of a fund in a certain year generally contains only little information about the future return that the fund will generate. Finally, we have information on the investments in different mutual funds made by a small subgroup of investors known to have been exposed to both the atp...... five crowns to funds with the lowest costs and one crown to funds with the highest costs. We investigate the ability of the atpRating to predict the future performance of a fund. We find that an investor who has invested in the funds with the lowest costs within an investment category would have...

  20. O papel das aves na dispersão e germinação de sementes do pau-incenso (Pittoporum undulatum Vent. em um remanescente de Mata Atlântica. Bird role in seed dispersion and germination of Pittosporum undulatum Vent., seeds in an Atlantic Forest remnant.

    Directory of Open Access Journals (Sweden)

    Mariana Lopes CAMPAGNOLI

    2016-06-01

    Full Text Available A invasão biológica pela espécie Pittosporum undulatum Vent. pode ocasionar degradação de ecossistemas nativos, perda de espécies e de serviços ecossistêmicos. Além das características biológicas que favorecem seu estabelecimento, seus frutos são fontes alimentares para algumas espécies de aves, que acabam por dispersar suas sementes. O presente estudo foi realizado no Parque Estadual Alberto Löfgren, e visou verificar as espécies de aves potencialmente dispersoras do pau-incenso, comparar os registros de alimentação obtidos para esta árvore e para outras seis espécies arbóreas locais e avaliar a influência da ingestão das sementes pelas aves na sua taxa de germinação. A coleta de dados consistiu em observações focais das aves em atividade de forrageio no pau-incenso e a captura de indivíduos com redes de neblina para coleta de sementes nas fezes. Testes de germinação foram realizados com as sementes coletadas das fezes e diretamente dos frutos maduros. No total, foram encontradas 107 sementes nas fezes de oito sabiás, pertencentes a três espécies: Turdus rufiventris, Turdus amaurochalinus e Turdus albicollis. Não encontramos diferenças significativas nas taxas de germinação entre os tratamentos. Apesar da passagem das sementes pelo trato digestório das aves não ter alterado significativamente as taxas de germinação, os sabiás podem ser importantes dispersores do pau-incenso, permitindo a colonização de novas áreas por esta espécie exótica e intensificando seu processo de invasão biológica na Mata Atlântica.Biological invasion by the species Pittosporum undulatum Vent. could bring degradation to native ecosystems and loss of biodiversity and ecological services. Besides the biological features favoring the establishment of the species in natural environments, some bird species use its fruits as food sources, being responsible for its seed dispersion. The present study was held at Alberto L

  1. Dieta e dispersão de sementes por Cerdocyon thous (Linnaeus (Carnívora, Canidae, em um fragmento florestal no Paraná, Brasil Diet and seed dispersal by Cerdocyon thous (Linnaeus in a forest fragment in Paraná (Carnivora, Canidae

    Directory of Open Access Journals (Sweden)

    Vlamir J. Rocha

    2004-12-01

    Full Text Available Embora o cachorro-do-mato, Cerdocyon thous (Linnaeus, 1706, seja um Canidae relativamente comum, não há muita informação sobre sua dieta e seu papel como dispersor de sementes nos diferentes habitats onde ocorre. O objetivo deste trabalho foi o de reportar a dieta de C. thous e sua importância como dispersor e/ou predador de sementes, e ainda testar a taxa de germinação de sementes após passar pelo trato digestório do animal. O estudo foi realizado em um fragmento (680 ha de Floresta Estacional Semidecidual, o Parque Estadual Mata dos Godoy, localizado na cidade de Londrina, Paraná, sul do Brasil. A metodologia consistiu de coletas de fezes de C. thous, as quais foram analisadas em laboratório para identificar os itens consumidos. Nos testes de germinação, as sementes foram dispostas para germinar em placas de Petri com algodão umedecido em água. Noventa e três amostras fecais com 219 itens de origem vegetal e animal foram registradas, sendo 36,52% contendo restos de pequenos roedores, 24,19% de gramíneas, 13,24% de aves, 10,47% de insetos, 6,39% de Syagrus romanzoffiana (Cham. Glassm., 4,6% de outros itens de origem animal e 4,54% de outros itens de origem vegetal. Ainda, C. thous dispersou nove espécies de plantas, com relevante importância para a germinação de algumas sementes que passaram pelo trato digestório do animal, exceto para S. romanzoffiana, cujas sementes não germinaram nas condições de laboratório. Conclui-se que, C. thous apresentou uma dieta generalista e oportunista, sobrevivendo em áreas degradadas e antrópicas, e agindo como dispersor de sementes nestes locais.Although the crab eating fox, Cerdocyon thous (Linnaeus, 1706, is a relatively common Canidae, there isn't much information about its diet and its role as a seed disperser in the different habitats where it occurs. The aim of this work was to report the diet of the C. thous and its importance as a seed disperser and / or a seed predator and

  2. Habitat type and dispersal mode underlie the capacity for plant migration across an intermittent seaway.

    Science.gov (United States)

    Worth, J R P; Holland, B R; Beeton, N J; Schönfeld, B; Rossetto, M; Vaillancourt, R E; Jordan, G J

    2017-10-17

    Investigating species distributions across geographic barriers is a commonly utilized method in biogeography to help understand the functional traits that allow plants to disperse successfully. Here the biogeographic pattern analysis approach is extended by using chloroplast DNA whole-genome 'mining' to examine the functional traits that have impacted the dispersal of widespread temperate forest species across an intermittent seaway, the 200 km wide Bass Strait of south-eastern Australia. Multiple, co-distributed species of both dry and wet forests were sampled from five regions on either side of the Strait to obtain insights into past dispersal of these biomes via seed. Using a next-generation sequencing-based pool-seq method, the sharing of single nucleotide polymorphisms (SNPs) was estimated between all five regions in the chloroplast genome. A total of 3335 SNPs were detected in 20 species. SNP sharing patterns between regions provided evidence for significant seed-mediated gene flow across the study area, including across Bass Strait. A higher proportion of shared SNPs in dry forest species, especially those dispersed by birds, compared with wet forest species suggests that dry forest species have undergone greater seed-mediated gene flow across the study region during past climatic oscillations and sea level changes associated with the interglacial/glacial cycles. This finding is consistent with a greater propensity for long-distance dispersal for species of open habitats and proxy evidence that expansive areas of dry vegetation occurred during times of exposure of Bass Strait during glacials. Overall, this study provides novel genetic evidence that habitat type and its interaction with dispersal traits are major influences on dispersal of plants. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

  3. An ecosystem services approach to the ecological effects of salvage logging: valuation of seed dispersal.

    Science.gov (United States)

    Leverkus, Alexandro B; Castro, Jorge

    2017-06-01

    Forest disturbances diminish ecosystem services and boost disservices. Because post-disturbance management intends to recover the greatest possible value, selling timber often prevails over other considerations. Ecological research has shown diverse effects of salvage logging, yet such research has focused on the biophysical component of post-disturbance ecosystems and lacks the link with human well-being. Here we bridge that gap under the ecosystem services framework by assessing the impact of post-fire management on a non-timber value. By employing the replacement cost method, we calculated the value of the post-fire natural regeneration of Holm oaks in southern Spain under three post-fire management options by considering the cost of planting instead. The value of this ecosystem service in non-intervention areas doubled that of salvage-logged stands due to the preference for standing dead trees by the main seed disperser. Still, most of the value resulted from the resprouting capacity of oaks. The value of this and other ecosystem services should be added to traditional cost/benefit analyses of post-disturbance management. We thus call for a more holistic approach to salvage logging research, one that explicitly links ecological processes with human well-being through ecosystem services, to better inform decision-makers on the outcomes of post-disturbance management. © 2017 by the Ecological Society of America.

  4. [Maintaining solidarity: is mutuality the solution?].

    Science.gov (United States)

    Gevers, J K M; Ploem, M C

    2013-01-01

    Solidarity is essentially the willingness to contribute to the community and its demands, which may even involve contributing more than one is expecting to receive. Another principle is mutuality: this refers to a balance between rights and obligations or between mutual obligations. In its advisory document 'The importance of mutuality......solidarity takes work!', The Dutch Council for Public Health and Health Care underlines the importance of ensuring solidarity within the Dutch health care system, e.g. by encouraging patients to take responsibility for their own health, possibly by introducing elements of mutuality. In our contribution, we comment on the Council's advice. Although we fully agree with the overall conclusion that solidarity should be maintained within the system, we do not see how the introduction of increased mutuality will contribute to this goal.

  5. Germination and dormancy of single tomato seeds : a study using non-invasive molecular and biophysical techniques

    NARCIS (Netherlands)

    Spoelstra, P.

    2002-01-01

    Formation , germination and dormancy of seeds are important steps in the life cycle of higher plants. The seed is the generative dispersal unit, which enables plants to spread and survive through periods or seasons of less favourable conditions. In agriculture tomato is

  6. Seed Removal Increased by Scramble Competition with an Invasive Species.

    Science.gov (United States)

    Minor, Rebecca L; Koprowski, John L

    2015-01-01

    Competition for seeds has a major influence on the evolution of granivores and the plants on which they rely. The complexity of interactions and coevolutionary relationships vary across forest types. The introduction of non-native granivores has considerable potential to alter seed dispersal dynamics. Non-native species are a major cause of endangerment for native species, but the mechanisms are often unclear. As biological invasions continue to rise, it is important to understand mechanisms to build up strategies to mitigate the threat. Our field experiment quantified the impact of introduced Abert's squirrels (Sciurus aberti) on rates of seed removal within the range of critically endangered Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis), which consumes similar foods. In the presence of invasive Abert's squirrels, the time cones were removed was faster than when the invasive was excluded, accounting for a median removal time of cones available to red and Abert's squirrels that is 32.8% less than that of cones available only to the rare native red squirrels. Moreover, in the presence of Abert's squirrels, removal rates are higher at great distance from a territorial red squirrel larderhoard and in more open portions of the forest, which suggests differential patterns of seed dispersal. The impact on food availability as a result of cone removal by Abert's squirrels suggests the potential of food competition as a mechanism of endangerment for the Mount Graham red squirrel. Furthermore, the magnitude and differential spatial patterns of seed removal suggest that non-native granivores may have impacts on forest regeneration and structure.

  7. Seed Removal Increased by Scramble Competition with an Invasive Species.

    Directory of Open Access Journals (Sweden)

    Rebecca L Minor

    Full Text Available Competition for seeds has a major influence on the evolution of granivores and the plants on which they rely. The complexity of interactions and coevolutionary relationships vary across forest types. The introduction of non-native granivores has considerable potential to alter seed dispersal dynamics. Non-native species are a major cause of endangerment for native species, but the mechanisms are often unclear. As biological invasions continue to rise, it is important to understand mechanisms to build up strategies to mitigate the threat. Our field experiment quantified the impact of introduced Abert's squirrels (Sciurus aberti on rates of seed removal within the range of critically endangered Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis, which consumes similar foods. In the presence of invasive Abert's squirrels, the time cones were removed was faster than when the invasive was excluded, accounting for a median removal time of cones available to red and Abert's squirrels that is 32.8% less than that of cones available only to the rare native red squirrels. Moreover, in the presence of Abert's squirrels, removal rates are higher at great distance from a territorial red squirrel larderhoard and in more open portions of the forest, which suggests differential patterns of seed dispersal. The impact on food availability as a result of cone removal by Abert's squirrels suggests the potential of food competition as a mechanism of endangerment for the Mount Graham red squirrel. Furthermore, the magnitude and differential spatial patterns of seed removal suggest that non-native granivores may have impacts on forest regeneration and structure.

  8. Interim evaluation report of the mutually operable database systems by different computers; Denshi keisanki sogo un'yo database system chukan hyoka hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1989-03-01

    This is the interim report on evaluation of the mutually operable database systems by different computers. The techniques for these systems fall into four categories of those related to (1) dispersed data systems, (2) multimedia, (3) high reliability, and (4) elementary techniques for mutually operable network systems. The techniques for the category (1) include those for vertically dispersed databases, database systems for multiple addresses in a wide area, and open type combined database systems, which have been in progress generally as planned. Those for the category (2) include the techniques for color document inputting and information retrieval, meaning compiling, understanding highly overlapping data, and controlling data centered by drawings, which have been in progress generally as planned. Those for the category (3) include the techniques for improving resistance of the networks to obstruction, and security of the data in the networks, which have been in progress generally as planned. Those for the category (4) include the techniques for rule processing for development of protocols, protocols for mutually connecting the systems, and high-speed, high-function networks, which have been in progress generally as planned. It is expected that the original objectives are finally achieved, because the development programs for these categories have been in progress generally as planned. (NEDO)

  9. Were Malagasy Uncarina fruits dispersed by the extinct elephant bird?

    Directory of Open Access Journals (Sweden)

    N. Illing

    2010-02-01

    Full Text Available We hypothesise that the spiny fruits of the endemic Madagascar
    genus Uncarina (Pedaliaceae are trample burrs that evolved to be
    dispersed on the feet of the extinct elephant bird (Aepyornis. Our
    evidence is: i the morphology of the fruit with its large grapple
    hooks is more likely to attach to a foot than to adhere to fur and
    ii the presentation of mature fruits on the ground rather than in the
    canopy. These differences to adhesive burrs make lemurs unlikely
    dispersers. We argue, given the absence of other large terrestrial
    mammals in Madagascar, that the most likely dispersers of
    Uncarina fruits were the extinct large birds. If correct, our hypothesis
    has implications for conservation of Uncarina, the biogeography
    of the elephant birds and dispersal biology. For
    example, we predict that the demography of Uncarina will be
    skewed towards adult plants, and that the dispersal mutualism
    could possibly be rescued by domestic animals.

  10. Fruit and seed discoveries in Stichoneuron membranaceum Hook. f. (Stemonaceae: an endemic to Indo-Myanmar

    Directory of Open Access Journals (Sweden)

    Koushik Majumdar

    2013-04-01

    Full Text Available Stichoneuron membranaceum Hook. f. is an endemic species of Indo-Myanmar hotspot whose fruit and seed remained unknown to science since 1850, until they were collected from Tripura, Northeast India. Based on these gatherings, this study is the first report about the development and morphological features of fruit and seed. Earlier historical collections of this species were discussed. Its preferred habitat, possible pollinating agents and seed dispersal mechanism were also investigated.

  11. Mutually-modulated cross-gain modulation and slow light

    International Nuclear Information System (INIS)

    Sternklar, Shmuel; Sarid, Eyal; Wart, Maxim; Granot, Er'el

    2010-01-01

    The interaction of pump and Stokes light in a Brillouin medium, where both beams are modulated, can be utilized for controlling the group velocity of the amplified Stokes (or depleted pump). The dependence of the group velocity for this mutually-modulated cross-gain modulation (MMXGM) technique on the Brillouin gain parameter is studied. A sharp transition to slow light occurs in the G 1 α/β≈1 regime, where G 1 is the Brillouin gain parameter, and α and β are the pump and Stokes modulation indices, respectively. A comparison of MMXGM slow light to the Brillouin dispersion-based slow-light technique reveals the fundamental differences between them. The formation of higher harmonics of the modulation frequency is also discussed. The theoretical predictions are experimentally corroborated and potential applications in fiber-based sensing and interferometry are discussed

  12. Entanglement in mutually unbiased bases

    Energy Technology Data Exchange (ETDEWEB)

    Wiesniak, M; Zeilinger, A [Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna (Austria); Paterek, T, E-mail: tomasz.paterek@nus.edu.sg [Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore (Singapore)

    2011-05-15

    One of the essential features of quantum mechanics is that most pairs of observables cannot be measured simultaneously. This phenomenon manifests itself most strongly when observables are related to mutually unbiased bases. In this paper, we shed some light on the connection between mutually unbiased bases and another essential feature of quantum mechanics, quantum entanglement. It is shown that a complete set of mutually unbiased bases of a bipartite system contains a fixed amount of entanglement, independent of the choice of the set. This has implications for entanglement distribution among the states of a complete set. In prime-squared dimensions we present an explicit experiment-friendly construction of a complete set with a particularly simple entanglement distribution. Finally, we describe the basic properties of mutually unbiased bases composed of product states only. The constructions are illustrated with explicit examples in low dimensions. We believe that the properties of entanglement in mutually unbiased bases may be one of the ingredients to be taken into account to settle the question of the existence of complete sets. We also expect that they will be relevant to applications of bases in the experimental realization of quantum protocols in higher-dimensional Hilbert spaces.

  13. Mutualism and impacts of global change: response of an important and neglected component of the biodiversity; Mutualisme et impacts des changements globaux: reponse d'une composante importante et negligee de la biodiversite

    Energy Technology Data Exchange (ETDEWEB)

    Hossaert-Mckey, M [Centre d' Ecologie Fonctionnelle et Evolutive (CEFE), UMR CNRS 5175, 34 - Montpellier (France)

    2007-07-01

    We are studying the impact of global change on two obligate species-specific insect-plant mutualisms. Our approach combines correlative methods (examining spatial patterns of genetic diversity in populations of pairs of mutualists, to examine their responses to past climate change) and experiments (studying responses of plant partners to CO{sub 2} fertilization). Mutualisms function because the partners have contrasting and complementary biological traits, so that a service implying only a low cost to one partner may confer a great benefit to the other. Because they can lead mutualist partners to respond differently to rapid ecological change, the biological differences that are fundamental to mutualisms may also make them vulnerable. Imbalances thereby introduced can disrupt the functioning of the mutualism. By comparing two strongly contrasting systems-fig/wasp pollination mutualisms and ant-plant protection mutualisms-we aim to characterize the diversity of responses of mutualisms to global change. By identifying points in common, we also aim to propose robust generalizations about the response to global change of obligate, specific mutualisms, an important and neglected component of tropical biodiversity. Our results show that the two mutualisms studied differ greatly in their response to Pleistocene and Holocene climatic fluctuations. Fig/wasp systems show little spatial genetic differentiation, indicating that the great dispersal capacities of both figs and their pollinating wasps resulted in maintenance of high effective population sizes throughout cycles of climatic and vegetation change. In contrast, limited dispersal capacity of both ant and plant partners has resulted in greater impact of climatic fluctuations on ant/plant protection mutualisms: species-distribution patterns suggest restriction of the system to refugia, and strong spatial genetic structure indicates widespread bottlenecks during fragmentation and expansion. Alternate contraction and

  14. Annual variations in seed yield and implications for multiple use of crabwood

    Directory of Open Access Journals (Sweden)

    Helio Tonini

    2017-12-01

    Full Text Available The objective of this study was to evaluate the annual variation in seed yield of crabwood, and discuss implications for multiple use management of the species. Data were collected in a forest area in the southern of Roraima State in a permanent plot of 9 ha (300 m x 300 m with a natural population of crabwood. Seed production was monitored of 115 trees during four years. Seed yield varied among years. May to July was the period of bigger yield. Few trees (22.6% concentrated the bigger part of seeds yield (80.7% and the most productive trees had diameter at 1.30 m above ground level between 40 cm - 70 cm. Therefore we recommend 70 cm as minimum cutting diameter for wood exploitation. For sustainable crabwood seed management we recommend to restrict seed collection from the most productive trees and only during the period of maximum seed dispersal.

  15. Empirical study on mutual fund objective classification.

    Science.gov (United States)

    Jin, Xue-jun; Yang, Xiao-lan

    2004-05-01

    Mutual funds are usually classified on the basis of their objectives. If the activities of mutual funds are consistent with their stated objectives, investors may look at the latter as signals of their risks and incomes. This work analyzes mutual fund objective classification in China by statistical methods of distance analysis and discriminant analysis; and examines whether the stated investment objectives of mutual funds adequately represent their attributes to investors. That is, if mutual funds adhere to their stated objectives, attributes must be heterogeneous between investment objective groups and homogeneous within them. Our conclusion is to some degree, the group of optimized exponential funds is heterogeneous to other groups. As a whole, there exist no significant differences between different objective groups; and 50% of mutual funds are not consistent with their objective groups.

  16. Effects of liana load, tree diameter and distances between conspecifics on seed production in tropical timber trees

    NARCIS (Netherlands)

    Nabe-Nielsen, J.; Kollmann, J.; Peña-Claros, M.

    2009-01-01

    Seed production in tropical timber trees is limited by abiotic resources, pollination and pre-dispersal seed predation. Resource availability is influenced by the number of competing trees and by lianas that often reach high densities in disturbed parts of tropical forests. The distance between

  17. The mutual dependence of M1 fertility and M2 mutations in rice

    International Nuclear Information System (INIS)

    Gopinathan Nair, V.

    1982-01-01

    The mutual dependence of M 1 fertility and M 2 mutations in rice was studied after treatment with gamma rays and EMS. The frequency of chlorophyll mutations increased with decrease in seed fertility when M 1 ears were selected at random. However, at the lowest fertility class the mutation frequency was low. This reduction is attributed to the elimination of mutants in the high sterility class. The mutation yield can therefore be significantly enhanced by selecting M 1 ears of low fertility. The segregation ratio of mutants increased as fertility decreased. Mutation spectrum was however not influenced by M 1 fertility. This makes selection for fertility quite ineffective in altering the mutation spectrum. (author)

  18. Small seed size increases the potential for dispersal of wetland plants by ducks

    NARCIS (Netherlands)

    Soons, M.B.; van der Vlugt, C.; van Lith, B.; Heil, G.W.; Klaassen, M.R.J.

    2008-01-01

    1. Long-distance dispersal (LDD) is important in plants of dynamic and ephemeral habitats. For plants of dynamic wetland habitats, waterfowl are generally considered to be important LDD vectors. However, in comparison to the internal (endozoochorous) dispersal of terrestrial plants by birds,

  19. Economic contract theory tests models of mutualism.

    Science.gov (United States)

    Weyl, E Glen; Frederickson, Megan E; Yu, Douglas W; Pierce, Naomi E

    2010-09-07

    Although mutualisms are common in all ecological communities and have played key roles in the diversification of life, our current understanding of the evolution of cooperation applies mostly to social behavior within a species. A central question is whether mutualisms persist because hosts have evolved costly punishment of cheaters. Here, we use the economic theory of employment contracts to formulate and distinguish between two mechanisms that have been proposed to prevent cheating in host-symbiont mutualisms, partner fidelity feedback (PFF) and host sanctions (HS). Under PFF, positive feedback between host fitness and symbiont fitness is sufficient to prevent cheating; in contrast, HS posits the necessity of costly punishment to maintain mutualism. A coevolutionary model of mutualism finds that HS are unlikely to evolve de novo, and published data on legume-rhizobia and yucca-moth mutualisms are consistent with PFF and not with HS. Thus, in systems considered to be textbook cases of HS, we find poor support for the theory that hosts have evolved to punish cheating symbionts; instead, we show that even horizontally transmitted mutualisms can be stabilized via PFF. PFF theory may place previously underappreciated constraints on the evolution of mutualism and explain why punishment is far from ubiquitous in nature.

  20. Seed shadow of Swietenia macrophylla remnant trees in a Mexican rainforest: Implications for forest management

    OpenAIRE

    Alcalá, Raúl E.; Alonso, Roxalma L.; Gutiérrez-Granados, Gabriel

    2014-01-01

    The understanding of processes affecting the regeneration and coexistence of tree species is of high concern in tropical landscapes disturbed by anthropogenic activities. In this study, we evaluated the seed shadow of eight small remnant Swietenia macrophylla trees to determine the possible consequences of selective logging on the first stages of natural regeneration. We expected to find a restricted dispersal ability and a marked loss of seeds due to biotic interactions. To test this, seed s...

  1. Mutual funds: temporary problem or permanent morass?

    OpenAIRE

    Paula A. Tkac

    2004-01-01

    The improprieties in the mutual fund industry that surfaced in the fall of 2003 prompted the passage and drafting of legislation and regulations that cover nearly every facet of mutual fund pricing and operations. While this regulatory flurry is clearly intended to protect shareholders’ interests, the question remains: How will these scandals and regulatory changes ultimately affect mutual fund investors? ; When considering the problems inherent in mutual fund management and the best ways to ...

  2. Predispersal infestation of Vochysia haenkeana seeds by Lius conicus

    Directory of Open Access Journals (Sweden)

    Samara Letícia Oliveira Lourenço

    Full Text Available ABSTRACT: The deficient development of fertile seeds of native forest plant species in Brazil limits the reproduction of these plants in various conditions. Among the limiting biotic factors in quality and quantity of the forest seeds, borer insects are quite prominent, before and after their dispersion. This study reports for the first time a host of the buprestid beetle Lius conicus (Gory & Laporte, 1840. The larval development of L. conicus takes place in the seed capsules of Vochysia haenkeana Mart. (Vochysiaceae, a typical tree species in the Brazilian cerrado biome. In two regions of the cerrado in Goiás State, Brazil, almost ripe fruits of V. haenkeana were collected directly from the plants. After natural drying, and fruit and seed processing in laboratory, damage caused by the L. conicus larvae was quantified and qualified. Bigger fruits were preferred as hosts. Fruits developing on the eastern side of the plant were most frequently occupied by L. conicus. Seed lots of bigger fruits showed damage up to 37.5% from the infestation by L. conicus larvae. There was only one larva per fruit, which damaged all the seeds of the capsule (three or four and generally consumed around 26% of the seed dry mass.

  3. Mutualism and impacts of global change: response of an important and neglected component of the biodiversity; Mutualisme et impacts des changements globaux: reponse d'une composante importante et negligee de la biodiversite

    Energy Technology Data Exchange (ETDEWEB)

    Hossaert-Mckey, M. [Centre d' Ecologie Fonctionnelle et Evolutive (CEFE), UMR CNRS 5175, 34 - Montpellier (France)

    2007-07-01

    We are studying the impact of global change on two obligate species-specific insect-plant mutualisms. Our approach combines correlative methods (examining spatial patterns of genetic diversity in populations of pairs of mutualists, to examine their responses to past climate change) and experiments (studying responses of plant partners to CO{sub 2} fertilization). Mutualisms function because the partners have contrasting and complementary biological traits, so that a service implying only a low cost to one partner may confer a great benefit to the other. Because they can lead mutualist partners to respond differently to rapid ecological change, the biological differences that are fundamental to mutualisms may also make them vulnerable. Imbalances thereby introduced can disrupt the functioning of the mutualism. By comparing two strongly contrasting systems-fig/wasp pollination mutualisms and ant-plant protection mutualisms-we aim to characterize the diversity of responses of mutualisms to global change. By identifying points in common, we also aim to propose robust generalizations about the response to global change of obligate, specific mutualisms, an important and neglected component of tropical biodiversity. Our results show that the two mutualisms studied differ greatly in their response to Pleistocene and Holocene climatic fluctuations. Fig/wasp systems show little spatial genetic differentiation, indicating that the great dispersal capacities of both figs and their pollinating wasps resulted in maintenance of high effective population sizes throughout cycles of climatic and vegetation change. In contrast, limited dispersal capacity of both ant and plant partners has resulted in greater impact of climatic fluctuations on ant/plant protection mutualisms: species-distribution patterns suggest restriction of the system to refugia, and strong spatial genetic structure indicates widespread bottlenecks during fragmentation and expansion. Alternate contraction and

  4. Endocarp thickness affects seed removal speed by small rodents in a warm-temperate broad-leafed deciduous forest, China

    Science.gov (United States)

    Zhang, Hongmao; Zhang, Zhibin

    2008-11-01

    Seed traits are important factors affecting seed predation by rodents and thereby the success of recruitment. Seeds of many tree species have hard hulls. These are thought to confer mechanical protection, but the effect of endocarp thickness on seed predation by rodents has not been well investigated. Wild apricot ( Prunus armeniaca), wild peach ( Amygdalus davidiana), cultivated walnut ( Juglans regia), wild walnut ( Juglans mandshurica Maxim) and Liaodong oak ( Quercus liaotungensis) are very common tree species in northwestern Beijing city, China. Their seeds vary greatly in size, endocarp thickness, caloric value and tannin content. This paper aims to study the effects of seed traits on seed removal speed of these five tree species by small rodents in a temperate deciduous forest, with emphasis on the effect of endocarp thickness. The results indicated that speed of removal of seeds released at stations in the field decreased significantly with increasing endocarp thickness. We found no significant correlations between seed removal speed and other seed traits such as seed size, caloric value and tannin content. In seed selection experiments in small cages, Père David's rock squirrel ( Sciurotamias davidianus), a large-bodied, strong-jawed rodent, selected all of the five seed species, and the selection order among the five seed species was determined by endocarp thickness and the ratio of endocarp mass/seed mass. In contrast, the Korean field mouse ( Apodemus peninsulae) and Chinese white-bellied rat ( Niviventer confucianus), with relatively small bodies and weak jaws, preferred to select small seeds like acorns of Q. liaotungensis and seeds of P. armeniaca, indicating that rodent body size is also an important factor affecting food selection based on seed size. These results suggest endocarp thickness significantly reduces seed removal speed by rodents and then negatively affects dispersal fitness of seeds before seed removal of tree species in the study

  5. Comparison of investment opportunities in mutual funds

    OpenAIRE

    NOVÁKOVÁ, Petra

    2012-01-01

    This thesis deals with the comparison of selected mutual funds in the Czech Republic. The main aim of this thesis is to evaluate the situation on the securities market of mutual funds and help to the investor with right choice of mutual fund. Work is initially devoted to the characteristics and history of collective investment. The following section describes mutual funds their characteristics, classification, creation and termination. Conclusion of the theoretical part is devoted to investme...

  6. Sino-U.S. Strategic Mutual Trust

    Institute of Scientific and Technical Information of China (English)

    Yuan Peng; Zhang Yimeng

    2008-01-01

    Relations between China and the U.S. have been relatively stable for nearly seven years, for the first time since the end of the Cold War. Strategic mutual trust, however, is not enough and there is a long way to go before both countries can achieve a permanent strategic stability. Four problems have prevented stability in bilateral relations, namely structural, internal, accidental, and cognitive issues. The goal of building strategic mutual trust still remains distant, and developing a good understanding between each other is the thorniest problem for both countries. Better mutual understanding can lead to an expansion of bilateral relations. China and the U.S. need to increase mutual trust and work towards achieving strategic stability.

  7. A parameter-free community detection method based on centrality and dispersion of nodes in complex networks

    Science.gov (United States)

    Li, Yafang; Jia, Caiyan; Yu, Jian

    2015-11-01

    K-means is a simple and efficient clustering algorithm to detect communities in networks. However, it may suffer from a bad choice of initial seeds (also called centers) that seriously affect the clustering accuracy and the convergence rate. Additionally, in K-means, the number of communities should be specified in advance. Till now, it is still an open problem on how to select initial seeds and how to determine the number of communities. In this study, a new parameter-free community detection method (named K-rank-D) was proposed. First, based on the fact that good initial seeds usually have high importance and are dispersedly located in a network, we proposed a modified PageRank centrality to evaluate the importance of a node, and drew a decision graph to depict the importance and the dispersion of nodes. Then, the initial seeds and the number of communities were selected from the decision graph actively and intuitively as the 'start' parameter of K-means. Experimental results on synthetic and real-world networks demonstrate the superior performance of our approach over competing methods for community detection.

  8. From seed production to seedling establishment: Important steps in an invasive process

    Science.gov (United States)

    Ferreras, Ana Elisa; Galetto, Leonardo

    2010-03-01

    It is widely accepted that exotic invasive species are one of the most important ecological and economic problems. Reproductive and establishment traits are considered key features of a population expansion process, but few works have studied many of these simultaneously. This work examines how large the differences are in reproductive and establishment traits between two Fabaceae, the exotic invasive, Gleditsia triacanthos and the native, Acacia aroma. Gleditsia is a serious leguminous woody invader in various parts of the world and Acacia is a common native tree of Argentina. Both species have similar dispersal mechanisms and their reproductive phenology overlaps. We chose 17 plants of each species in a continuous forest of the Chaco Serrano Forest of Córdoba, Argentina. In each plant we measured fruit production, fruit removal (exclusion experiments), seed predation (pre- and post-dispersal), seed germination, seed bank (on each focal tree, three sampling periods during the year), and density of seedlings (around focal individuals and randomly in the study site). Gleditsia presented some traits that could favour the invasion process, such as a higher number of seeds per plant, percentage of scarified seed germination and density of seedlings around the focal individuals, than Acacia. On the other hand, Gleditsia presented a higher percentage of seed predation. The seed bank was persistent in both species and no differences were observed in fruit removal. This work highlights the importance of simultaneously studying reproductive and establishment variables involved in the spreading of an exotic invasive species. It also gives important insight into the variables to be considered when planning management strategies. The results are discussed from the perspective of some remarkable hypotheses on invasive species and may contribute to rethinking some aspects of the theory on invasive species.

  9. Fruit dispersal and seed banks in Atriplex sagittata: the role of heterocarpy

    Czech Academy of Sciences Publication Activity Database

    Mandák, Bohumil; Pyšek, Petr

    2001-01-01

    Roč. 89, - (2001), s. 159-165 ISSN 0022-0477 R&D Projects: GA AV ČR KSK2005601 Institutional research plan: CEZ:AV0Z6005908 Keywords : Atriplex sagittata * Chenopodiaceae * seed bank Subject RIV: EF - Botanics Impact factor: 2.291, year: 2001

  10. Performance Evaluation of Equity Mutual Funds in Indonesia

    Directory of Open Access Journals (Sweden)

    Irene Rini Demi Pangestuti

    2017-11-01

    Full Text Available Mutual funds considered as an investment alternative for investors. One type of mutual fund that attracts many investors was the equity mutual funds. Equity mutual fund is a type of mutual funds that most part of the investment consists of stocks in the capital market so the risk rate was higher than the other types of mutual funds. For its different characteristic, the measurement for equity funds performance did not be same with other types of mutual funds. As a stock portfolio, equity mutual funds can be measured by portfolio measurement methods such as Sharpe Index, Treynor Ratio, Jensen Index, Adjusted Sharpe Index, Adjusted Jensen Index, and Sortino Ratio. This study was conducted by using all of those performance measurements as most research in Indonesia was conducted by using limited performance measurements (focusing on Sharpe Index, Treynor Ratio, and Jensen Index. This study aims to evaluated the performance of 42 equity mutual funds available in Indonesia by employing Sharpe Index, Treynor Ratio, Jensen Index, Adjusted Sharpe Index (ASI, Adjusted Jensen Index (AJI, and Sortino Ratio because most previous researches in Indonesian setting disregards ASI and AJI. In general, it was concluded that the SAM Indonesian Equity was the best performing equity fund during the study period. It was further found that most equity mutual fund studied have been well diversified.

  11. Explaining mutualism variation: a new evolutionary paradox?

    Science.gov (United States)

    Heath, Katy D; Stinchcombe, John R

    2014-02-01

    The paradox of mutualism is typically framed as the persistence of interspecific cooperation, despite the potential advantages of cheating. Thus, mutualism research has tended to focus on stabilizing mechanisms that prevent the invasion of low-quality partners. These mechanisms alone cannot explain the persistence of variation for partner quality observed in nature, leaving a large gap in our understanding of how mutualisms evolve. Studying partner quality variation is necessary for applying genetically explicit models to predict evolution in natural populations, a necessary step for understanding the origins of mutualisms as well as their ongoing dynamics. An evolutionary genetic approach, which is focused on naturally occurring mutualist variation, can potentially synthesize the currently disconnected fields of mutualism evolution and coevolutionary genetics. We outline explanations for the maintenance of genetic variation for mutualism and suggest approaches necessary to address them. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

  12. 12 CFR 563.74 - Mutual capital certificates.

    Science.gov (United States)

    2010-01-01

    ... the funds for redemption are raised by the issuance of mutual capital certificates approved pursuant... 12 Banks and Banking 5 2010-01-01 2010-01-01 false Mutual capital certificates. 563.74 Section 563...-OPERATIONS Securities and Borrowings § 563.74 Mutual capital certificates. (a) General. No savings...

  13. The distribution of fruit and seed toxicity during development for eleven neotropical trees and vines in Central Panama.

    Directory of Open Access Journals (Sweden)

    Noelle G Beckman

    Full Text Available Secondary compounds in fruit mediate interactions with natural enemies and seed dispersers, influencing plant survival and species distributions. The functions of secondary metabolites in plant defenses have been well-studied in green tissues, but not in reproductive structures of plants. In this study, the distribution of toxicity within plants was quantified and its influence on seed survival was determined in Central Panama. To investigate patterns of allocation to chemical defenses and shifts in allocation with fruit development, I quantified variation in toxicity between immature and mature fruit and between the seed and pericarp for eleven species. Toxicity of seed and pericarp was compared to leaf toxicity for five species. Toxicity was measured as reduced hyphal growth of two fungal pathogens, Phoma sp. and Fusarium sp., and reduced survivorship of brine shrimp, Artemia franciscana, across a range of concentrations of crude extract. I used these measures of potential toxicity against generalist natural enemies to examine the effect of fruit toxicity on reductions of fruit development and seed survival by vertebrates, invertebrates, and pathogens measured for seven species in a natural enemy removal experiment. The seed or pericarp of all vertebrate- and wind-dispersed species reduced Artemia survivorship and hyphal growth of Fusarium during the immature and mature stages. Only mature fruit of two vertebrate-dispersed species reduced hyphal growth of Phoma. Predispersal seed survival increased with toxicity of immature fruit to Artemia during germination and decreased with toxicity to fungi during fruit development. This study suggests that fruit toxicity against generalist natural enemies may be common in Central Panama. These results support the hypothesis that secondary metabolites in fruit have adaptive value and are important in the evolution of fruit-frugivore interactions.

  14. The distribution of fruit and seed toxicity during development for eleven neotropical trees and vines in Central Panama.

    Science.gov (United States)

    Beckman, Noelle G

    2013-01-01

    Secondary compounds in fruit mediate interactions with natural enemies and seed dispersers, influencing plant survival and species distributions. The functions of secondary metabolites in plant defenses have been well-studied in green tissues, but not in reproductive structures of plants. In this study, the distribution of toxicity within plants was quantified and its influence on seed survival was determined in Central Panama. To investigate patterns of allocation to chemical defenses and shifts in allocation with fruit development, I quantified variation in toxicity between immature and mature fruit and between the seed and pericarp for eleven species. Toxicity of seed and pericarp was compared to leaf toxicity for five species. Toxicity was measured as reduced hyphal growth of two fungal pathogens, Phoma sp. and Fusarium sp., and reduced survivorship of brine shrimp, Artemia franciscana, across a range of concentrations of crude extract. I used these measures of potential toxicity against generalist natural enemies to examine the effect of fruit toxicity on reductions of fruit development and seed survival by vertebrates, invertebrates, and pathogens measured for seven species in a natural enemy removal experiment. The seed or pericarp of all vertebrate- and wind-dispersed species reduced Artemia survivorship and hyphal growth of Fusarium during the immature and mature stages. Only mature fruit of two vertebrate-dispersed species reduced hyphal growth of Phoma. Predispersal seed survival increased with toxicity of immature fruit to Artemia during germination and decreased with toxicity to fungi during fruit development. This study suggests that fruit toxicity against generalist natural enemies may be common in Central Panama. These results support the hypothesis that secondary metabolites in fruit have adaptive value and are important in the evolution of fruit-frugivore interactions.

  15. Seed germination from lowland tapir (Tapirus terrestris) fecal samples collected during the dry season in the Northern Brazilian Amazon.

    Science.gov (United States)

    Barcelos, Adriana Renata; Bobrowiec, Paulo Estefano D; Sanaiotti, Tânia Margarete; Gribel, Rogério

    2013-03-01

    This study evaluated the potential of lowland tapirs as seed dispersers in the northern Brazilian Amazon. The study analyzed the viability of seeds after passage through the gut. Fecal samples were collected from 6 different vegetation physiognomies in Viruá National Park during the dry season. The samples were then kept in a greenhouse for 16 months to allow the seeds to germinate. The seedling species were identified and classified according to the type of fruit, plant habit, seed size and type of ingestion. Of the 111 fecal samples, 94 (84.7%) had viable seeds of 75 species. Melastomataceae was the most frequent family with viable seeds in the fecal samples (69.1% of samples, N= 18 species). The data suggest that the importance of the lowland tapirs as dispersers is not restricted to the species consumed actively by frugivory but also extends to species accidentally consumed during browsing. The occurrence of both large and small viable seeds in the fecal samples as well as a number of large drupes, which probably cannot be transported via endozoochory by any other animal species, provide evidence of the ecological importance of lowland tapirs to the dynamics of the forest-campinarana vegetation mosaic in the region. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

  16. Dispersal and colonisation of plants in lowland streams: success rates and bottlenecks

    DEFF Research Database (Denmark)

    Riis, Tenna

    2008-01-01

    -rich lowland streams. Rather, I conclude that primary colonisation is the main constraint to regaining vegetation in lowland streams in general and in vegetation-free rehabilitated streams in particular. Therefore, if plant colonisation is a target for stream rehabilitation, it is important to enhance......Plant dispersal and colonisation, including rates of dispersal, retention, colonisation and survival of dispersed propagules (shoots and seeds), were studied in a 300-m stream reach in a macrophyte-rich lowland stream during one growing season. Relationships between colonisation processes...... and simple flow parameters were tested. Each fortnight during a growing season, the number of dispersed plant propagules and the number of new and lost plant colonisations since the last sampling day were recorded. The retention of dispersing shoots was tested on two occasions during the growing season...

  17. Asset Allocation of Mutual Fund Investors

    OpenAIRE

    Dengpan Luo

    2003-01-01

    This paper studies mutual fund investors' asset allocation decisions using monthly flow data of U.S mutual fund industry from 1984 to 1998. We find that mutual fund investors change their asset allocations between stocks and bonds in reaction to business conditions tracked by changes in expected stock market returns. They tend to allocate less into stock funds during the trough of a business cycle when expected stock market returns are higher and to allocate more into stock funds during the p...

  18. Pilot Testing of a Sampling Methodology for Assessing Seed Attachment Propensity and Transport Rate in a Soil Matrix Carried on Boot Soles and Bike Tires

    Science.gov (United States)

    Hardiman, Nigel; Dietz, Kristina Charlotte; Bride, Ian; Passfield, Louis

    2017-01-01

    Land managers of natural areas are under pressure to balance demands for increased recreation access with protection of the natural resource. Unintended dispersal of seeds by visitors to natural areas has high potential for weedy plant invasions, with initial seed attachment an important step in the dispersal process. Although walking and mountain biking are popular nature-based recreation activities, there are few studies quantifying propensity for seed attachment and transport rate on boot soles and none for bike tires. Attachment and transport rate can potentially be affected by a wide range of factors for which field testing can be time-consuming and expensive. We pilot tested a sampling methodology for measuring seed attachment and transport rate in a soil matrix carried on boot soles and bike tires traversing a known quantity and density of a seed analog (beads) over different distances and soil conditions. We found % attachment rate on boot soles was much lower overall than previously reported, but that boot soles had a higher propensity for seed attachment than bike tires in almost all conditions. We believe our methodology offers a cost-effective option for researchers seeking to manipulate and test effects of different influencing factors on these two dispersal vectors.

  19. Pilot Testing of a Sampling Methodology for Assessing Seed Attachment Propensity and Transport Rate in a Soil Matrix Carried on Boot Soles and Bike Tires.

    Science.gov (United States)

    Hardiman, Nigel; Dietz, Kristina Charlotte; Bride, Ian; Passfield, Louis

    2017-01-01

    Land managers of natural areas are under pressure to balance demands for increased recreation access with protection of the natural resource. Unintended dispersal of seeds by visitors to natural areas has high potential for weedy plant invasions, with initial seed attachment an important step in the dispersal process. Although walking and mountain biking are popular nature-based recreation activities, there are few studies quantifying propensity for seed attachment and transport rate on boot soles and none for bike tires. Attachment and transport rate can potentially be affected by a wide range of factors for which field testing can be time-consuming and expensive. We pilot tested a sampling methodology for measuring seed attachment and transport rate in a soil matrix carried on boot soles and bike tires traversing a known quantity and density of a seed analog (beads) over different distances and soil conditions. We found % attachment rate on boot soles was much lower overall than previously reported, but that boot soles had a higher propensity for seed attachment than bike tires in almost all conditions. We believe our methodology offers a cost-effective option for researchers seeking to manipulate and test effects of different influencing factors on these two dispersal vectors.

  20. Windows of opportunity for germination of riparian species after restoring water level fluctuations: a field experiment with controlled seed banks

    NARCIS (Netherlands)

    Sarneel, J.M.; Janssen, R.H.; Rip, W.J.; Bender, I.; Bakker, E.S.

    2014-01-01

    Restoration activities aiming at increasing vegetation diversity often try to stimulate both dispersal and germination. In wetlands, dispersal and germination are coupled as water and water level fluctuations (WLF) simultaneously influence seed transport and germination conditions (soil moisture).

  1. Evaluation of essential minerals in pumpkin seeds by EDXRF; Avaliacao de minerais essenciais em sementes de abobora moranga por EDXRF

    Energy Technology Data Exchange (ETDEWEB)

    Boaro, Flavia Araujo; Zacari, Cristiane Z. [Faculdades Metropolitanas Unidas (FMU), Sao Paulo, SP (Brazil); Scapin, Marcos A.; Aquino, Reginaldo R. [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Sao Paulo, SP(Brazil)

    2013-07-01

    Pumpkin seeds, marketed in the Municipal Market of Sao Paulo, Brazil, were analyzed using the Energy Dispersive of X-ray Fluorescence technique (EDXRF) seeking to evaluate the content of the main essential minerals present in these seeds, and their contribution to human nutrition.

  2. Impacts of logging on density-dependent predation of dipterocarp seeds in a South East Asian rainforest.

    Science.gov (United States)

    Bagchi, Robert; Philipson, Christopher D; Slade, Eleanor M; Hector, Andy; Phillips, Sam; Villanueva, Jerome F; Lewis, Owen T; Lyal, Christopher H C; Nilus, Reuben; Madran, Adzley; Scholes, Julie D; Press, Malcolm C

    2011-11-27

    Much of the forest remaining in South East Asia has been selectively logged. The processes promoting species coexistence may be the key to the recovery and maintenance of diversity in these forests. One such process is the Janzen-Connell mechanism, where specialized natural enemies such as seed predators maintain diversity by inhibiting regeneration near conspecifics. In Neotropical forests, anthropogenic disturbance can disrupt the Janzen-Connell mechanism, but similar data are unavailable for South East Asia. We investigated the effects of conspecific density (two spatial scales) and distance from fruiting trees on seed and seedling survival of the canopy tree Parashorea malaanonan in unlogged and logged forests in Sabah, Malaysia. The production of mature seeds was higher in unlogged forest, perhaps because high adult densities facilitate pollination or satiate pre-dispersal predators. In both forest types, post-dispersal survival was reduced by small-scale (1 m(2)) conspecific density, but not by proximity to the nearest fruiting tree. Large-scale conspecific density (seeds per fruiting tree) reduced predation, probably by satiating predators. Higher seed production in unlogged forest, in combination with slightly higher survival, meant that recruitment was almost entirely limited to unlogged forest. Thus, while logging might not affect the Janzen-Connell mechanism at this site, it may influence the recruitment of particular species.

  3. Seed quality in informal seed systems

    NARCIS (Netherlands)

    Biemond, P.C.

    2013-01-01

    Keywords: informal seed systems, seed recycling, seed quality, germination, seed pathology, seed health, seed-borne diseases, mycotoxigenic fungi, Fusarium verticillioides, mycotoxins, Vigna unguiculata, Zea mays, Nigeria.

    Seed is a crucial input for agricultural production.

  4. Effect of Time and Burial Depth on Breaking Seed dormancy and Germination of Weed Seeds

    Directory of Open Access Journals (Sweden)

    marzie mazhari

    2016-02-01

    Full Text Available Introduction: Weeds limit crop growth, development and yield through competing. Seed bank of weeds in field is one of the sources which can affect weed management and their control methods. Environmental conditions during seed maturation and following dispersal interact to influence the germination phenology of many species. Disturbance plays a key role in the maintenance of habitat for many plant species, particularly referrals, for example, fire ephemerals, desert annuals, and arable weeds. Seed germination and emergence depend on endogenous and exogenous factors. Viable seeds are dormant when all environmental conditions are appropriate for germination but seeds fail to germinate. Thus, dormancy plays an important ecological role in preventing seed germination, being a major contributor to seed persistence of some species in soil. Buried seeds of annual weeds are certainly subjected to different soil moisture conditions during their dormancy release season (winter according to the annual rainfall pattern and burial depth. Shallow buried seeds are exposed to soil moisture fluctuations that could affect their dormancy status. Laboratory studies showed that desiccation and subsequent re-hydration of seeds could stimulate germination and modify seed light requirements. Seeds buried in deeper layers of the soil would not be exposed to such fluctuations in soil moisture, but would be exposed to different soil moisture environments depending on weather and soil characteristics. The effects of interactions between temperature, and soil or seed moisture, on seed dormancy changes have been reported for several species. Therefore, the objectives of this study were to determine the effect of time and burial depth treatments on seed germination and seedling emergence of Aegilops cylindrica, Agropyrom repens, Avena fatua, Bromus dantoniae, Cynodon dactylon, Cyprus rotundus, Setaria viridis, Anthriscus sylvestris, Centurea cyanus. Materials and Methods: In

  5. Ecological interactions shape the dynamics of seed predation in Acrocomia aculeata (Arecaceae).

    Science.gov (United States)

    Pereira, Anielle C F; Fonseca, Francine S A; Mota, Gleicielle R; Fernandes, Ane K C; Fagundes, Marcílio; Reis-Júnior, Ronaldo; Faria, Maurício L

    2014-01-01

    The complex network of direct and indirect relationships determines not only the species abundances but also the community characteristics such as diversity and stability. In this context, seed predation is a direct interaction that affects the reproductive success of the plant. For Acrocomia aculeata, the seed predation by Pachymerus cardo and Speciomerus revoili in post-dispersal may destroy more than 70% of the propagules and is influenced by the herbivory of the fruits during pre-dispersal. Fruits of plants with a higher level of herbivory during pre-dispersal are less attacked by predators in post-dispersal. We proposed a hypothesis that describes this interaction as an indirect defense mediated by fungi in a multitrophic interaction. As explanations, we proposed the predictions: i) injuries caused by herbivores in the fruits of A. aculeata favor fungal colonization and ii) the colonization of A. acuelata fruit by decomposing fungi reduces the selection of the egg-laying site by predator. For prediction (i), differences in the fungal colonization in fruits with an intact or damaged epicarp were evaluated in fruits exposed in the field. For prediction (ii), we performed fruit observations in the field to determine the number of eggs of P. cardo and/or S. revoili per fruit and the amount of fungal colonization in the fruits. In another experiment, in the laboratory, we use P. cardo females in a triple-choice protocol. Each insect to choose one of the three options: healthy fruits, fruits with fungus, or an empty pot. The proposed hypothesis was corroborated. Fruits with injuries in the epicarp had a higher fungal colonization, and fruits colonized by fungi were less attractive for egg-laying by seed predators. This study emphasizes the importance of exploring the networks of interactions between multitrophic systems to understand the dynamics and maintenance of natural populations.

  6. Ecological Interactions Shape the Dynamics of Seed Predation in Acrocomia aculeata (Arecaceae)

    Science.gov (United States)

    Pereira, Anielle C. F.; Fonseca, Francine S. A.; Mota, Gleicielle R.; Fernandes, Ane K. C.; Fagundes, Marcílio; Reis-Júnior, Ronaldo; Faria, Maurício L.

    2014-01-01

    Background The complex network of direct and indirect relationships determines not only the species abundances but also the community characteristics such as diversity and stability. In this context, seed predation is a direct interaction that affects the reproductive success of the plant. For Acrocomia aculeata, the seed predation by Pachymerus cardo and Speciomerus revoili in post-dispersal may destroy more than 70% of the propagules and is influenced by the herbivory of the fruits during pre-dispersal. Fruits of plants with a higher level of herbivory during pre-dispersal are less attacked by predators in post-dispersal. We proposed a hypothesis that describes this interaction as an indirect defense mediated by fungi in a multitrophic interaction. As explanations, we proposed the predictions: i) injuries caused by herbivores in the fruits of A. aculeata favor fungal colonization and ii) the colonization of A. acuelata fruit by decomposing fungi reduces the selection of the egg-laying site by predator. Methodology/Principal Findings For prediction (i), differences in the fungal colonization in fruits with an intact or damaged epicarp were evaluated in fruits exposed in the field. For prediction (ii), we performed fruit observations in the field to determine the number of eggs of P. cardo and/or S. revoili per fruit and the amount of fungal colonization in the fruits. In another experiment, in the laboratory, we use P. cardo females in a triple-choice protocol. Each insect to choose one of the three options: healthy fruits, fruits with fungus, or an empty pot. The proposed hypothesis was corroborated. Fruits with injuries in the epicarp had a higher fungal colonization, and fruits colonized by fungi were less attractive for egg-laying by seed predators. Conclusion/Significance This study emphasizes the importance of exploring the networks of interactions between multitrophic systems to understand the dynamics and maintenance of natural populations. PMID:24875386

  7. Mutual benefits in academic-service partnership: An integrative review.

    Science.gov (United States)

    Sadeghnezhad, Maliheh; Heshmati Nabavi, Fatemeh; Najafi, Fereshteh; Kareshki, Hossein; Esmaily, Habibollah

    2018-05-30

    Academic and service institutions involve with many challenges. Partnership programs are a golden opportunity to achieve mutual benefits to overcome these challenges. Identifying mutual benefits is the cornerstone of forming a successful partnership and guarantee to its continuity. There are definitions and instances of mutual benefits in the literature related to partnership programs, but there is no coherent evidence and clear picture of these benefits. This study is conducted to identify mutual benefits in academic-service partnership by analyzing the definitions and instances of it in the literature. An integrative review of key papers regarding mutual benefits in academic-service partnership was undertaken. This review was guided by the framework described by Whittemore and Knafl. Search of the following databases was conducted: MEDLINE, ERIC, Google Scholar, Emerald Insight and Science Direct. The search terms were mutual benefits, mutual gains, mutual interest, mutual expectations, mutual goals, mutual demand, partnership, collaboration, academic-service partnership and academic service collaboration. Cooper's five-stage integrative review method was used. Quality evaluation of articles was conducted. Data were abstracted from included articles. The analysis was conducted based on the qualitative content analysis of the literature suggested by Zhang and Wildemuth. 28 articles were included in this review. Mutual benefits are described in four categories include: synergy in training and empowerment of human resources, education improvement, access to shared resources, facilitate production and application of beneficial knowledge into practice. Mutual benefits in the academic-service partnership include a range of goals, interests, expectations, and needs of partner organizations that is achievable and measurable through joint planning and collaboration. We suggest academic and service policymakers to consider these benefits in the planning and evaluating

  8. Danish mutual fund performance

    DEFF Research Database (Denmark)

    Christensen, Michael

    2013-01-01

    This article provides the first independent performance analysis of Danish mutual funds. We analyse selectivity and market timing abilities for 71 mutual funds that have been in operation from 2001 to 2010. The results show great fund performance diversity. Half the funds have performed neutrally......, whereas 42% of the funds have shown significantly negative performance and only 7% of the funds have over-performed their benchmark. Furthermore, 14% of the funds analysed possess market timing abilities, but for 8 out of 10 funds, their market timing ability has been unsuccessful....

  9. Trading Cost Management of Mutual Funds

    NARCIS (Netherlands)

    R. Xing (Rang)

    2016-01-01

    textabstractThis paper documents the trading behaviour of actively managed equity mutual funds from the perspective of their trading cost management. Consistent with the predictions in the literature of portfolio choice with trading costs, I present three main findings. Firstly, mutual funds trade

  10. Dispersal syndromes in the largest protection area of the Atlantic Forest in the state of Paraiba, Brazil

    Directory of Open Access Journals (Sweden)

    Camila Ângelo Jerônimo Domingues

    2013-09-01

    Full Text Available The diaspore dispersal process is crucial for plant reproduction, since the diaspores must reach a suitable site to germinate. This paper aimed to study morphological aspects of diaspores and determine the dispersal syndromes of species occurring in the largest protection area of the Atlantic Forest in the state of Paraiba, Brazil, the Guaribas Biological Reserve. One conducted a monthly collection of fruits/seeds within the period from September 2007 to February 2009. All diaspores of the fruiting species were collected. After analyzing characteristics such as fruit and seed consistency, odor, color, size, and weight, one determined the dispersal syndrome of each species. One collected 3,080 diaspores belonging to 136 different species distributed into 27 families. Zoochory was the most abundant dispersal syndrome (58%, with 79 fruits adapted to it, followed by autochory (29%, and anemochory (13%. Throughout the study period, one found fruiting species, with a predominance of zoochoric fruits, a predictable fact in the Atlantic Forest, which provides fleshy fruits all the year round.

  11. THE PERFORMANCE OF MUTUAL FUNDS IN SLOVAKIA

    Directory of Open Access Journals (Sweden)

    F. Tudorache

    2016-11-01

    Full Text Available A good indicator for the financial markets performance in different countries is the evolution of mutual funds in terms of their inflows and outflows. The goal of the present paper is to analyse the performance of the mutual funds in Slovakia. The research objectives are twofold: to study the flows of funds into and out of mutual funds from Slovakia during the period 2007-2014 and to analyse how investors in Slovakian mutual funds behave in terms of their investment choice. The analysis focuses on identifying patterns in investors' decision making process and on examining the similarity of their behavioural patterns with the ones identi¬fied at international level.

  12. Seed dormancy and germination in Jeffersonia dubia (Berberidaceae) as affected by temperature and gibberellic acid.

    Science.gov (United States)

    Rhie, Y H; Lee, S Y; Kim, K S

    2015-03-01

    The genus Jeffersonia, which contains only two species, has a trans-Atlantic disjunct distribution. The aims of this study were to determine the requirements for breaking dormancy and germination of J. dubia seeds and to compare its dormancy characteristics with those of the congener in eastern North America. Ripe seeds of J. dubia contain an underdeveloped embryo and were permeable to water. In nature, seeds were dispersed in May, while embryos began to grow in September, and were fully elongated by late November. Germination started in March of the next year, and seeds emerged as seedlings soon after germination. In laboratory experiments, incubation at high temperatures (25 °C, 25/15 °C) for at least 8 weeks was required to initiate embryo growth, while a transfer to moderate temperatures (20/10 °C, 15/6 °C) was needed for the completion of embryo growth. At least 8 weeks at 5 °C was effective in overcoming physiological dormancy and for germination in seeds after the embryos had fully elongated. Thus, both high and low temperatures were essential to break dormancy. Gibberellic acid (GA3 ) treatment could substitute for the high temperature requirement, but not for the low temperature requirement. Based on the dormancy-breaking requirements, it is confirmed that the seeds have deep simple morphophysiological dormancy. This dormancy type is similar to that of seeds of the eastern North American species J. diphylla. Although seeds require 10-11 months from seed dispersal to germination in nature, under controlled conditions they required only 3 months after treatment with 1000 mg·l(-1) GA3 , followed by incubation at 15/6 °C. This represents practical knowledge for propagation of these plants from seed. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

  13. Seed maturation in Arabidopsis thaliana is characterized by nuclear size reduction and increased chromatin condensation.

    Science.gov (United States)

    van Zanten, Martijn; Koini, Maria A; Geyer, Regina; Liu, Yongxiu; Brambilla, Vittoria; Bartels, Dorothea; Koornneef, Maarten; Fransz, Paul; Soppe, Wim J J

    2011-12-13

    Most plant species rely on seeds for their dispersal and survival under unfavorable environmental conditions. Seeds are characterized by their low moisture content and significantly reduced metabolic activities. During the maturation phase, seeds accumulate storage reserves and become desiccation-tolerant and dormant. Growth is resumed after release of dormancy and the occurrence of favorable environmental conditions. Here we show that embryonic cotyledon nuclei of Arabidopsis thaliana seeds have a significantly reduced nuclear size, which is established at the beginning of seed maturation. In addition, the chromatin of embryonic cotyledon nuclei from mature seeds is highly condensed. Nuclei regain their size and chromatin condensation level during germination. The reduction in nuclear size is controlled by the seed maturation regulator ABSCISIC ACID-INSENSITIVE 3, and the increase during germination requires two predicted nuclear matrix proteins, LITTLE NUCLEI 1 and LITTLE NUCLEI 2. Our results suggest that the specific properties of nuclei in ripe seeds are an adaptation to desiccation, independent of dormancy. We conclude that the changes in nuclear size and chromatin condensation in seeds are independent, developmentally controlled processes.

  14. Seed regulations and local seed systems

    NARCIS (Netherlands)

    Louwaars, N.

    2000-01-01

    Seed regulations have been introduced in most countries based on the development of formal seed production. Concerns about seed quality and about the varietal identity of the seeds have commonly led to seed laws. However, formal regulations are often inappropriate for informal seed systems, which

  15. Contributions of long-distance dispersal to population growth in colonising Pinus ponderosa populations.

    Science.gov (United States)

    Lesser, Mark R; Jackson, Stephen T

    2013-03-01

    Long-distance dispersal is an integral part of plant species migration and population development. We aged and genotyped 1125 individuals in four disjunct populations of Pinus ponderosa that were initially established by long-distance dispersal in the 16th and 17th centuries. Parentage analysis was used to determine if individuals were the product of local reproductive events (two parents present), long-distance pollen dispersal (one parent present) or long-distance seed dispersal (no parents present). All individuals established in the first century at each site were the result of long-distance dispersal. Individuals reproduced at younger ages with increasing age of the overall population. These results suggest Allee effects, where populations were initially unable to expand on their own, and were dependent on long-distance dispersal to overcome a minimum-size threshold. Our results demonstrate that long-distance dispersal was not only necessary for initial colonisation but also to sustain subsequent population growth during early phases of expansion. © 2012 Blackwell Publishing Ltd/CNRS.

  16. Effect of human disturbance on seed and seedling distribution of the Andean Oak (Quercus humboldtii Bonpl., Fagaceae) in the Colombian Eastern Cordillera

    International Nuclear Information System (INIS)

    Guerrero Rodriguez, Sandra Bibiana; Paz Camacho, Erika Andrea; Parrado Rosselli, Angela

    2010-01-01

    Animals affect the spatial occupation patterns of tropical forest plants throughout the seed dispersal they perform. Therefore, changes in vertebrate populations by human disturbance might affect re generation dynamics of plant species. We studied differences in the spatial distribution of seeds and seedlings of the Andean oak (Quercus humboldtii) between two nearby forests with contrasting levels of anthropogenic influence in the Colombian Andes. Density and spatial distribution of seedlings were evaluated in 490 and 484 1 m2 plots located in a 28 ha area, in the high and low disturbed site, respectively. In each plot, all seedlings found were sampled and classified into three age categories. Density and spatial distribution of seeds were evaluated in 0.25 m 2s ubplots placed in the same plots described above. Results showed a higher number and density of seedlings in the high disturbed site, as well as a marked decrease in seedling density as age increases. Distances to the nearest neighbour were shorter in the high disturbed site for all seedlings and each age category, in contrast to the low disturbed site. Indexes of spatial distribution indicate an aggregated pattern in the most disturbed site, while a uniform pattern in the low disturbed one. Seeds also exhibited an aggregated pattern in the high disturbed site and a higher seed predation by invertebrates. Results seemed to be a consequence of forest fragmentation and a decrease of vertebrate seed dispersers, seed predators and herbivores associated to the regeneration processes of the species. These results provide important information for the forest management and restoration activities, since in order to maintain plant populations in the long term, presence and viable populations of seed dispersers should be also maintained.

  17. Patrones de dispersión de semillas y colonización de Misodendrum punctulatum (Misodendraceae en un matorral postfuego de Nothofagus antarctica (Nothofagaceae del noroeste de la Patagonia Misodendrum punctulatum (Misodendraceae seed dispersal and colonization patterns on a Nothofagus antarctica (Nothofagaceae post-fire shrubland from Northwestern Patagonia

    Directory of Open Access Journals (Sweden)

    NORLAN TERCERO-BUCARDO

    2010-01-01

    resultados de este trabajo podrían ser útiles en proyectos de restauración ecológica, por ejemplo para la reintroducción de M. puctulatum sobre ejemplares de N. antárctica que rebrotan en matorrales postfuegos. Estos aspectos estudiados también aportan al conocimiento de esta interacción ecológica que ocurre frecuentemente en los bosques de Nothofagus de Argentina y Chile.Spatial dispersal pattern could determine the spatial pattern of establishment affecting the vegetation structure. Our work, analyze dispersion and colonization attribute of the hemiparasitic plant Misodendrum punctulatum (Misodendraceae. Our hypothesis outline that the wind dispersal pattern of M. punctulatum seeds determine the infection pattern (colonization on Nothofagus antárctica, and both processes (dispersión and colonization are asymmetric in accordance with the predominant wind direction. This study was carry out in a N. antárctica (host post-fire shrubland. We assessed the seed dispersal estimating number of seed on host branches supplied from infected-survivals hosts (focal host toward each cardinal direction. Colonization was assessed estimating number of infections on each host, through transects, at every cardinal direction from the focal host. We observed that seeds dispersed decline with distances from the seed source, and dispersion fitted to a negative exponential model. The longest distance of primary dispersion observed was 10 m toward east. About colonization, longest distance from the focal host was 22.5 m toward south. Furthermore, ratio of infected host was lesser on west, one infected by 10 uninfected (1:10 than other compass aspects (1:6. Both process, dispersion and colonization, showed a similar and asymmetric pattern of distribution, which could be result of wind direction predominant from northwest. In addition, a high spatial correlation was observed among number of seed dispersed and recruitment of infection in distances from the sources of seeds. Our results

  18. Regeneration in natural and logged tropical rain forest : modelling seed dispersal and regeneration

    NARCIS (Netherlands)

    Ulft, Lambertus Henricus van

    2004-01-01

    Regeneration and disturbance are thought to play key roles in the maintenance of the high tree species diversity in tropical rain forests. Nevertheless, the earliest stages in the regeneration of tropical rain forest trees, from seed production to established seedlings, have received little

  19. Variation in Weed Seed Fate Fed to Different Holstein Cattle Groups.

    Directory of Open Access Journals (Sweden)

    Salman Rahimi

    Full Text Available Weed seeds may maintain their viability when passing through the digestive tract of cattle and can be therefore dispersed by animal movement or the application of manure. Whether different cattle types of the same species can cause differential weed seed fate is largely unknown to us particularly under non-grazed systems similar to Holstein-Friesian dairy farming. We investigated the effect on the seed survival of four weed species in the digestive tracts of four groups of Holstein cattle: lactating cows, feedlot male calves, dry cows and growing heifers. The weed species used were Cuscuta campestris, Polygonum aviculare, Rumex crispus and Sorghum halepense. Cattle excretion was sampled for recovery and viability of seeds at four 24 hourly intervals after seed intake. The highest seed recovery occurred two days after seed intake in all cattle groups. Averaged over weed species, dry and lactating cows had the lowest and highest seed recovery of 36.4% and 74.4% respectively. No significant differences were observed in seed recovery of the four weed species when their seeds were fed to dry cows. Based on a power model fitted to seed viability data, the estimated time to 50% viability loss after seed intake, over all cattle groups ranged from 65 h (R. crispus to 76 h (P. aviculare. Recovered seeds from the dung of feedlot male calves showed the highest mortality among cattle groups. Significant correlation was found between seed viability and ruminal pH (r = 0.86; P<0.05. This study shows that management programs aiming to minimize weed infestation caused by livestock should account for the variation amongst cattle groups in seed persistence. Our findings can be used as a guideline for evaluating the potential risk of the spread of weeds via the application of cattle manure.

  20. Variation in Weed Seed Fate Fed to Different Holstein Cattle Groups.

    Science.gov (United States)

    Rahimi, Salman; Mashhadi, Hamid Rahimian; Banadaky, Mehdi Dehghan; Mesgaran, Mohsen Beheshtian

    2016-01-01

    Weed seeds may maintain their viability when passing through the digestive tract of cattle and can be therefore dispersed by animal movement or the application of manure. Whether different cattle types of the same species can cause differential weed seed fate is largely unknown to us particularly under non-grazed systems similar to Holstein-Friesian dairy farming. We investigated the effect on the seed survival of four weed species in the digestive tracts of four groups of Holstein cattle: lactating cows, feedlot male calves, dry cows and growing heifers. The weed species used were Cuscuta campestris, Polygonum aviculare, Rumex crispus and Sorghum halepense. Cattle excretion was sampled for recovery and viability of seeds at four 24 hourly intervals after seed intake. The highest seed recovery occurred two days after seed intake in all cattle groups. Averaged over weed species, dry and lactating cows had the lowest and highest seed recovery of 36.4% and 74.4% respectively. No significant differences were observed in seed recovery of the four weed species when their seeds were fed to dry cows. Based on a power model fitted to seed viability data, the estimated time to 50% viability loss after seed intake, over all cattle groups ranged from 65 h (R. crispus) to 76 h (P. aviculare). Recovered seeds from the dung of feedlot male calves showed the highest mortality among cattle groups. Significant correlation was found between seed viability and ruminal pH (r = 0.86; Pweed infestation caused by livestock should account for the variation amongst cattle groups in seed persistence. Our findings can be used as a guideline for evaluating the potential risk of the spread of weeds via the application of cattle manure.

  1. Longitudinal analysis of mutual fund performance

    NARCIS (Netherlands)

    Ter Horst, J.R.

    1998-01-01

    Many different motivations for investing in mutual funds have been provided in the literature, including the claim that managers of mutual funds have special abilities that can be used to outperform the market. Testing of the validity of these claims is complicated by two facts. First, the expected

  2. All dispersal functions are wrong, but many are useful: A response to Cousens etal.

    Czech Academy of Sciences Publication Activity Database

    Bullock, J. M.; Hooftman, D. A. P.; Tamme, R.; Götzenberger, Lars; Pärtel, M.; González, L. M.; White, S. M.

    2018-01-01

    Roč. 106, č. 3 (2018), s. 907-910 ISSN 0022-0477 Institutional support: RVO:67985939 Keywords : seed dispersal * probability density function * prediction Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 5.813, year: 2016

  3. Mutual Fund Flight-to-Liquidity

    DEFF Research Database (Denmark)

    Rzeznik, Aleksandra

    This paper examines the liquidity choices of mutual funds during times of market uncertainty. I find that when markets are uncertain, mutual funds actively increase the liquidity of their portfolio – often referred to as a ‘flight-to-liquidity.’ In aggregate, mutual fund behaviour has implications...... for the market; the market driven flight-toliquidity places upward pressure on the liquidity premium. I examine the underlying mechanisms driving fund behaviour. I show that market volatility is associated with lower fund performance and withdrawals, which causes funds to adjust the composition...... of their portfolio towards more liquid assets in order to meet potential redemptions. This causal chain is consistent with Vayanos (2004), who argues that fund managers are investors with time-varying liquidity preferences due to threat of withdrawal. Aggregated over funds, the effect is substantial: a one standard...

  4. Mutual Fund Flight-to-Liquidity

    DEFF Research Database (Denmark)

    Rzeznik, Aleksandra

    This paper examines the liquidity choices of mutual funds during times of market uncertainty. I find that when markets are uncertain, mutual funds actively increase the liquidity of their portfolio { often referred to as a `flight-to-liquidity.' In aggregate, mutual fund behaviour has implications...... for the market; the market driven flight-toliquidity places upward pressure on the liquidity premium. I examine the underlying mechanisms driving fund behaviour. I show that market volatility is associated with lower fund performance and withdrawals, which causes funds to adjust the composition...... of their portfolio towards more liquid assets in order to meet potential redemptions. This causal chain is consistent with Vayanos (2004), who argues that fund managers are investors with time-varying liquidity preferences due to threat of withdrawal. Aggregated over funds, the effect is substantial: a one standard...

  5. EGYPTIAN MUTUAL FUNDS ANALYSIS: HISTORY, PERFORMANCE, OBJECTIVES, RISK AND RETURN

    Directory of Open Access Journals (Sweden)

    Petru STEFEA

    2013-10-01

    Full Text Available The present research aims to overview the mutual fund in Egypt. The establishment of the first mutual funds was achieved in 1994. Nowadays, the total mutual funds reached 90 funds , approximately. The income funds represent the largest share of the Egyptian mutual funds (40%, growth funds (25% and the private equity funds is at least (1%. The total population of the Egyptian mutual funds reached 22. Finally, the study proved that the Egyptian mutual funds have an impact on fund return , total risk and systemic; when analysis relationship between risk and return. The study found influencing for mutual fund's objectives on Sharpe and Terynor ratios.

  6. Revisiting Mutual Fund Performance Evaluation

    OpenAIRE

    Angelidis, Timotheos; Giamouridis, Daniel; Tessaromatis, Nikolaos

    2012-01-01

    Mutual fund manager excess performance should be measured relative to their self-reported benchmark rather than the return of a passive portfolio with the same risk characteristics. Ignoring the self-reported benchmark introduces biases in the measurement of stock selection and timing components of excess performance. We revisit baseline empirical evidence in mutual fund performance evaluation utilizing stock selection and timing measures that address these biases. We introduce a new factor e...

  7. Same magnetic nanoparticles, different heating behavior: Influence of the arrangement and dispersive medium

    Energy Technology Data Exchange (ETDEWEB)

    Andreu, Irene [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Campus Río Ebro, María de Luna, 3, 50018 Zaragoza (Spain); Natividad, Eva, E-mail: evanat@unizar.es [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Campus Río Ebro, María de Luna, 3, 50018 Zaragoza (Spain); Solozábal, Laura [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Campus Río Ebro, María de Luna, 3, 50018 Zaragoza (Spain); Roubeau, Olivier [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Departamento de Física de la Materia Condensada, 50009 Zaragoza (Spain)

    2015-04-15

    The heating ability of the same magnetic nanoparticles (MNPs) dispersed in different media has been studied in the 170–310 K temperature range. For this purpose, the biggest non-twinned nanoparticles have been selected among a series of magnetite nanoparticles of increasing sizes synthesized via a seeded growth method. The sample with nanoparticles dispersed in n-tetracosane, thermally quenched from 100 °C and solid in the whole measuring range, follows the linear response theoretical behavior for non-interacting nanoparticles, and displays a remarkably large maximum specific absorption rate (SAR) value comparable to that of magnetosomes at the alternating magnetic fields used in the measurements. The other samples, with nanoparticles dispersed either in alkane solvents of sub-ambient melting temperatures or in epoxy resin, display different thermal behaviors and maximum SAR values ranging between 11 and 65% of that achieved for the sample with n-tetracosane as dispersive medium. These results highlight the importance of the MNPs environment and arrangement to maintain optimal SAR values, and may help to understand the disparity sometimes found between MNPs heating performance measured in a ferrofluid and after injection in an animal model, where MNP arrangement and environment are not the same. - Highlights: • We synthetize a series of Fe{sub 3}O{sub 4} nanoparticles by the seeded-growth method. • We characterize the heating ability of 13.9 nm particles dispersed in several media. • We apply SAR(T) characterization to locate the onset of superparamagnetic behavior. • The highest SAR values are obtained in low-concentration solid-alkane dispersion. • Acquired arrangements in different media strongly modify SAR trends and values.

  8. Canopy seed banks as time capsules of biodiversity in pasture-remnant tree crowns.

    Science.gov (United States)

    Nadkarni, Nalini M; Haber, Willam A

    2009-10-01

    Tropical pastures present multiple barriers to tree regeneration and restoration. Relict trees serve as "regeneration foci" because they ameliorate the soil microclimate and serve as safe spots for dispersers. Here, we describe another mechanism by which remnant trees may facilitate pasture regeneration: the presence of seed banks in the canopy soil that accumulates from decomposing epiphytes within the crowns of mature remnant trees in tropical cloud forest pastures. We compared seed banks of canopy soils (histosols derived from fallen leaves, fruits, flower, and twigs of host trees and epiphytes, dead bryophytes, bark, detritus, dead animals, and microorganisms, and dust that accumulate on trunks and the upper surfaces of large branches) in pastures, canopy soils in primary forest trees, and soil on the forest floor in Monteverde, Costa Rica. There were 5211 epiphytic and terrestrial plant seeds in the three habitats. All habitats were dominated by seeds in a relatively small number of plant families, most of which were primarily woody, animal pollinated, and animal dispersed. The density of seeds on the forest floor was greater than seed density in either pasture-canopy or forest-canopy soils; the latter two did not differ. Eight species in 44 families and 61 genera from all of the habitats were tallied. There were 37 species in the pasture-canopy soil, 33 in the forest-canopy soil, and 57 on the forest floor. Eleven species were common to all habitats. The mean species richness in the pasture canopy was significantly higher than the forest canopy (F =83.38; p banks of pasture trees can function as time capsules by providing propagules that are removed in both space and time from the primary forest. Their presence may enhance the ability of pastures to regenerate more quickly, reinforcing the importance of trees in agricultural settings.

  9. A BIODEGRADABLE FILM FROM JACKFRUIT (ARTOCARPUS HETEROPHYLLUS AND DURIAN (DURIO ZIBETHINUS SEED FLOURS

    Directory of Open Access Journals (Sweden)

    Diah S. Retnowati

    2016-02-01

    Full Text Available The jackfruit (Artocarpus heterophyllus and durian (Durio zibethinus seeds contain high portion of amylose, which makes them potential materials for biodegradable films. The objective of this study is to develop biodegradable films composed of jackfruit and durian seed flours and glycerol as plasticizer. The films were prepared by dispersing flours in water, adding glycerol, heating the mixture, casting the solution on an acrylic plate, and drying the films at 50 ºC for 20 hours. Glycerol contributes to the flexibility of the film, while reduces the strength of the film. The Young’s modulus, tensile strength, and elongation at break increase as the ratio of jackfruit to durian seed flour increases. The films made from jackfruit and durian seed flours in this work are stronger than the film made from rice flour obtained by other researcher. Therefore, jackfruit and durian seed flours are potential raw material for biodegradable films.

  10. MUTUAL CONCESSIONS - SPECIFIC ELEMENT OF THE COMPROMISE/TRANSACTION CONTRACT

    Directory of Open Access Journals (Sweden)

    Georgeta-Bianca Spîrchez

    2012-11-01

    Full Text Available Given the usefulness and practical importance of the compromise contract conclusion and of the amicably dispute resolution, within the business world, we aim to analyze, in what follows, the concrete means by which these kind of settlement are achieved. Two questions become legitimate in the context of concerns about mutual concessions which the parties make in a compromise contract. These questions are the following: “What are the mutual concessions? Do mutual concessions mean equivalent concessions?” and “How mutual concessions are required to complete a valid settlement? Is the requirement of mutual concessions grounded?”

  11. Roles of mucilage in Emilia fosbergii, a myxocarpic Asteraceae: Efficient seed imbibition and diaspore adhesion.

    Science.gov (United States)

    De-Paula, Orlando C; Marzinek, Juliana; Oliveira, Denise M T; Paiva, Élder A S

    2015-09-01

    Several angiosperm families have myxodiaspory, such as the Asteraceae in which cypselae are frequently wind-dispersed. The roles of mucilage in cypselae remain misunderstood, and the route of water uptake from substrate to embryo remains unknown. In this work, we analyze the fruits of Emilia fosbergii aiming to clarify how the water is absorbed and how the structure of the pericarp can be related to the processes of diaspore adhesion and seed imbibition. The anatomy and ultrastructure of the cypselae of Emilia fosbergii were analyzed with histochemical tests and light, scanning and transmission electron microscopy. We assessed the roles of mucilage in seed imbibition using apoplasmic tracing with Lucifer yellow and epifluorescence microscopy and in adhesion with a sand assay. We describe structural and ultrastructural aspects of the exocarpic cells, especially the mucilaginous twin hairs. Lucifer yellow was absorbed only by the twin hairs, the cells where water primarily enters the seed during seed imbibition. In the sand assay, the mucilage was adhesive. The twin hairs on the surface of the cypselae can play a dual role in the establishment of new plants of this species. First, these trichomes constitute the main passage for water intake, which is essential for seed imbibition and germination, and after imbibition, they release mucilage that can adhere the diaspore. Therefore, the presence of myxocarpy in Asteraceae could be important in anemochoric species to avoid secondary dispersal. © 2015 Botanical Society of America.

  12. Mutual couling reduction using a lumped LC circuit

    DEFF Research Database (Denmark)

    Thaysen, Jesper; Jakobsen, Kaj Bjarne

    2004-01-01

    A technique to reduce the mutual coupling between two Planar Inverted F Antennas (PIFA) is presented in this paper. By the use of a parallel LC circuit it is possible to reduce the mutual coupling between two antennas. This results in a 16 % improvement in the radiation efficiency.......A technique to reduce the mutual coupling between two Planar Inverted F Antennas (PIFA) is presented in this paper. By the use of a parallel LC circuit it is possible to reduce the mutual coupling between two antennas. This results in a 16 % improvement in the radiation efficiency....

  13. Elections to the Mutual Aid Fund

    CERN Document Server

    2016-01-01

    Every two years, according to Article 6 of the Regulations of the Mutual Aid Fund, the Committee of the Mutual Aid Fund must renew one third of its membership. This year three members are outgoing. Of these three, two will stand again and one will not.   Candidates should be ready to give approximately two hours a month during working time to the Fund whose aim is to assist colleagues in financial difficulties. We invite applications from CERN Staff who wish to stand for election as a member of the CERN Mutual Aid Fund to send in their application before 17 June 2016, by email to the Fund’s President, Connie Potter (connie.potter@cern.ch).

  14. Measurement of particle velocity using a mutual inductance technique

    International Nuclear Information System (INIS)

    Kerr, Stephen; Kirkpatrick, Douglas; Garden, Steven

    2004-01-01

    Preliminary work on the development of a novel method for the measurement of particle velocity is described. The technique relies on measurement of the mutual inductance between two coaxial coils, one stationary and the other perturbed by the shock wave. The moving coil is the gauge and is deposited on thin film. The method was developed to assist in the study of particle velocities in large samples of porous media surrounding an explosive charge. The technique does not require measurements to be taken in a region of uniform magnetic field and therefore dispenses with the need for Helmholtz coils, the size and cost of which can become prohibitive for large experiments. This has the added advantage of allowing measurements to be taken at points widely dispersed through a sample with relative ease. Measurements of particle velocity in porous media have been compared with those from co-located conventional electromagnetic particle velocity gauges with reasonable agreement

  15. Mutuality

    DEFF Research Database (Denmark)

    Arnould, E. J.; Rose, A. S.

    2016-01-01

    and epistemological grounds and reproduces an array of problematic modernist dichotomies (e.g., agency/structure, nurturing family/instrumental public, gift/market, and altruism/self-interest) that significantly constrain the analytical enterprise. This work redresses some of the conceptual problems in the current...... formulation. The critique highlights a focus on resource distribution based on a more holistic, socially grounded perspective on circulation. We offer the alternative concept of mutuality or generalized exchange and the metaphor of inclusion rather than exchange as central to this perspective. We argue...

  16. PERFORMANCE OF SELECT MUTUAL FUNDS IN INDIA

    OpenAIRE

    Manoj Kumar Dash*

    2018-01-01

    Mutual funds is one of the major instruments for wealth creation and wealth saving in the current years. It is a financial instrument which gives positive result and satisfactory return to its investors. The mutual industries in have undergone a most successful phase in the last 15 years. The AUM has shown tremendous growth since inception from Rs. 25 crore in 1965 to Rs. 22,36,717 crore in December 2017. But this tremendous growth in the mutual fund industries in India is still lacking for b...

  17. Phylogeography and seed dispersal in islands: the case of Rumex bucephalophorus subsp. canariensis (Polygonaceae).

    Science.gov (United States)

    Talavera, María; Navarro-Sampedro, Laura; Ortiz, Pedro L; Arista, Montserrat

    2013-02-01

    Rumex bucephalophorus subsp. canariensis is an endemic taxon to Macaronesia with diaspore polymorphism. The origin and colonizing route of this taxon in Macaronesia was studied using molecular data and information on diaspore types. Amplified fragment length polymorphism (AFLP) was used in 260 plants from 22 populations of R. bucephalophorus subsp. canariensis, four from the Madeiran archipelago and 18 from the Canary archipelago. Diaspore production was analysed in 9-50 plants from each population used for AFLP analysis. One hundred and one plants from the Madeiran archipelago and 375 plants from the Canary Islands were studied. For each plant the type of diaspore produced was recorded. Overall populations had low genetic diversity but they showed a geographical pattern of genetic diversity that was higher in the older eastern islands than in the younger western ones. Two types of dispersible diaspores were found: in the eastern Canary islands (Lanzarote, Fuerteventura and Gran Canaria), plants produced exclusively long-dispersible diaspores, whereas in the western Canary islands (Tenerife, La Gomera, El Hierro) and the Madeiran archipelago plants produced exclusively short-dispersible diaspores. Genetically, the studied populations fell into four main island groups: Lanzarote-Fuerteventura, Gran Canaria, Tenerife-El Hierro and La Gomera-Madeira archipelago. A Moroccan origin of R. bucephalophorus subsp. canariensis is hypothesized with a colonization route from the eastern to the western islands. In addition, at least one gene flow event from La Gomera to the Madeiran archipelago has taken place. During the colonization process the type of dispersible diaspore changed so that dispersability decreased in populations of the westernmost islands.

  18. Fruit consumption and seed ispersal of Dimorphandra mollis Benth. (Leguminosae by the lowland tapir in the Cerrado of Central Brazil

    Directory of Open Access Journals (Sweden)

    M. X. A. Bizerril

    Full Text Available Fruit phenology observations and consumption of Dimorphandra mollis (Leguminosae were analyzed during seven months in an area of cerrado stricto sensu. We analysed 81 fecal samples collected at six different places of lowland tapirs (Tapirus terrestris in central Brazilian cerrado. In addition, from the feces of five tapirs at the Brasília Zoo to which fruit had been offered, seeds were collected and used in germination tests. The results suggest that the tapir is an important fruit consumer and a potential seed disperser of D. mollis. In the field, however, fruit consumption was found to be very low, probably because of both fruit palatability and the low density of frugivores, especially tapirs. The possibility that the original dispersal agents of D. mollis seeds belonged to the South American Pleistocene megafauna is discussed.

  19. Tree regeneration by seed in bottomland hardwood forests: A review

    Science.gov (United States)

    Kroschel, Whitney A.; King, Sammy L.; Keim, Richard F.

    2016-01-01

    Bottomland hardwood forests (BLH) are found in temperate, humid regions of the southeastern US, primarily on alluvial floodplains adjacent to rivers. Altered hydrology in rivers and floodplains has caused changes in stand development and species composition of BLHs. We hypothesize that the driving mechanisms behind these changes are related to the regeneration process because of the complexity of recruitment and the vulnerability of species at that age in development. Here we review the state of our understanding regarding BLH regeneration, and identify potential bottlenecks throughout the stages of seed production, seed dispersal, germination, establishment, and survival. Our process-level understanding of regeneration by seed in BLHs is rudimentary, thus limiting our ability to predict the effects of hydrologic alterations on species composition. By focusing future research on the appropriate stages of regeneration, we can better understand the sources of forest-community transitions across the diverse range of BLH systems.

  20. Mudaraba-Venture Capital Closed-end Mutual Funds and Mudaraba-Venture Capital Open-end Mutual Funds

    OpenAIRE

    Halil Ibrahim Bulut

    2008-01-01

    The important part of this study attempts to explain that both venture capital and interest-free financing are based on similar ground, if not the same. Two new models called Mudaraba-Venture Capital Closed-End Mutual Funds and Mudaraba-Venture Capital Open-End Mutual Funds, based on both the similarities and the needs of financial innovation in the interest-free financing system, are detailed. It is believed that the development of these two models could make some improvements not only in th...

  1. Water dispersal of vegetative bulbils of the invasive exotic Dioscorea oppositifolia L. in southern Illinois

    Science.gov (United States)

    Thomas, J.R.; Gibson, D.J.; Middleton, B.A.

    2005-01-01

    Riparian corridors promote dispersal of several species of exotic invasives worldwide. Dispersal plays a role in the colonization of exotic invasive species into new areas and this study was conducted to determine if the invasiveness of Dioscorea oppositifolia L. (Chinese yam) is facilitated by secondary dispersal of vegetative diaspores (bulbils) by water. Since seed production of this plant has not been observed in the United States, bulbils represent the only means of dispersal to new habitats. Dispersal was monitored by placing aquatic traps, tethered bulbils, and painted bulbil caches in a tributary of Drury Creek, Giant City State Park, Illinois. Results indicate that high-energy flow in the creek accelerated secondary dispersal of bulbils downstream and onto the floodplain. The longest recorded dispersal distance was 206.2 m downstream. Dispersal distance of tethered bulbils was not related to rainfall or flow velocity in the creek; however the total number of bulbils trapped was positively related to flow velocity. We conclude that secondary dispersal by water in streams can facilitate dispersal of vegetative bulbils of this exotic species.

  2. A multiscale approach to mutual information matching

    NARCIS (Netherlands)

    Pluim, J.P.W.; Maintz, J.B.A.; Viergever, M.A.; Hanson, K.M.

    1998-01-01

    Methods based on mutual information have shown promising results for matching of multimodal brain images. This paper discusses a multiscale approach to mutual information matching, aiming for an acceleration of the matching process while considering the accuracy and robustness of the method. Scaling

  3. Seed dispersal in limber and southwestern white pine: Comparing core and peripheral populations

    Science.gov (United States)

    Diana F. Tomback; Sheridan Samano; Elizabeth L. Pruett; Anna W. Schoettle

    2011-01-01

    According to the geographic mosaic theory of coevolution (Thompson 2005), the potential for coevolutionary relationships between interacting species varies with the presence of other species within a community. This implies that the strength of coevolution between two species may vary geographically. In this study, we ask whether there is a shift in vertebrate seed...

  4. Reducing Deviance Through Youths' Mutual Aid Group Dynamics.

    Science.gov (United States)

    Cheung, Chau-kiu; Ngai, Steven Sek-yum

    2016-01-01

    The mutual aid group, as supported by the social worker, emerges to play a vital role in helping group members reduce their deviance or behavioral problem. However, how the collaboration of the group and social worker accomplishes the reduction has remained uncharted. Based on social capital theory, mutual aid and cohesion within the group and social workers' specific aid for the group are likely responsible for the reduction. The test of such hypotheses relies on a two-wave panel survey of the members of 60 mutual aid groups who had deviant behavioral problems, located in Hong Kong, China. These groups had 241 youths completing both initial and 1-year follow-up surveys. Results manifested the direct or unconditional contributions of mutual aid, group cohesion, and social workers' specific aid to reducing deviance. Hence, social workers can enhance the effectiveness of the mutual aid group in reducing youths' deviance. © The Author(s) 2014.

  5. Environmental regulation of dormancy loss in seeds of Lomatium dissectum

    Science.gov (United States)

    Melissa Dawn Scholten

    2011-01-01

    Lomatium dissectum (Nutt.) Mathias & Constance is a perennial plant found across much of western North America. For disturbed lands within this range, there is interest in using L. dissectum in restoration. A problem in the propagation of L. dissectum is that at the time of dispersal the seeds are dormant. Thus, prior to usage in restoration projects the type of...

  6. Mutual funds : Management styles, social responsibility, performance and efficiency

    NARCIS (Netherlands)

    Barkó, Tamás; Renneboog, Luc; Baker, H.; Filbeck, G.; Kiymaz, H.

    2015-01-01

    The mutual fund industry represents a substantial part of global financial markets with approximately 20 percent invested in mutual funds. Mutual funds offer a simple and easy-to-understand way to invest either into stocks or fixed income products, both for retail and institutional investors. This

  7. Danish Mutual Fund Performance - Selectivity, Market Timing and Persistence

    DEFF Research Database (Denmark)

    Christensen, Michael

    Funds under management by Danish mutual funds have increased by 25% annually during the last 10 years and measured per capita Denmark has the third largest mutual fund industry in Europe. This paper provides the first independent performance analysis of Danish mutual funds. We analyse selectivity...

  8. Enhancement of local species richness in tundra by seed dispersal through guts of muskox and barnacle goose

    DEFF Research Database (Denmark)

    Bruun, Hans Henrik; Lundgren, Rebekka; Philipp, Marianne

    2008-01-01

    The potential contribution of vertebrate-mediated seed rain to the maintenance of plant community richness in a High Arctic ecosystem was investigated. We analyzed viable seed content in dung of the four numerically most important terrestrial vertebrates in Northeast Greenland - muskox (Ovibos...... moschatus), barnacle goose (Branta leucopsis), Arctic fox (Alopex lagopus) and Arctic hare (Lepus arcticus). High numbers of plant propagules were found in the dung of muskox and barnacle goose. Seeds of many plant species were found in the faeces of one vertebrate species only. Propagule composition...... in barnacle goose droppings was relatively uniform over samples, with a high abundance of the nutritious bulbils of Polygonum viviparum (Bistorta vivipara), suggesting that geese have a narrow habitat preference and feed selectively. Propagule composition in muskox dung was diverse and heterogeneous among...

  9. Mutually unbiased bases and semi-definite programming

    Energy Technology Data Exchange (ETDEWEB)

    Brierley, Stephen; Weigert, Stefan, E-mail: steve.brierley@ulb.ac.be, E-mail: stefan.weigert@york.ac.uk

    2010-11-01

    A complex Hilbert space of dimension six supports at least three but not more than seven mutually unbiased bases. Two computer-aided analytical methods to tighten these bounds are reviewed, based on a discretization of parameter space and on Groebner bases. A third algorithmic approach is presented: the non-existence of more than three mutually unbiased bases in composite dimensions can be decided by a global optimization method known as semidefinite programming. The method is used to confirm that the spectral matrix cannot be part of a complete set of seven mutually unbiased bases in dimension six.

  10. Mutually unbiased bases and semi-definite programming

    International Nuclear Information System (INIS)

    Brierley, Stephen; Weigert, Stefan

    2010-01-01

    A complex Hilbert space of dimension six supports at least three but not more than seven mutually unbiased bases. Two computer-aided analytical methods to tighten these bounds are reviewed, based on a discretization of parameter space and on Groebner bases. A third algorithmic approach is presented: the non-existence of more than three mutually unbiased bases in composite dimensions can be decided by a global optimization method known as semidefinite programming. The method is used to confirm that the spectral matrix cannot be part of a complete set of seven mutually unbiased bases in dimension six.

  11. Radioactive ceramic seeds with Ho-166 and Sm-153 with perspective of use in brachytherapy

    International Nuclear Information System (INIS)

    Valente, Eduardo Sarmento

    2010-01-01

    This work aimed to characterize physically, chemically and radioactively ceramics seeds with holmium and samarium embedded in ceramic matrix produced by sol-gel route. Biological response of HeLa cells was investigated macroscopically in vitro under the exposure to β radiation of Ho-166 and Sm-153. The dispersal of radioactive material in simulated body fluid (SBF) was made and the dose rate and total dose deposited in the volume delimited by the range of β particles in the water was calculated. The methodology used in physical, chemical and nuclear characterization was based on the following techniques: atomic emission spectrometry, neutron activation analysis, gamma spectrometry, X-ray fluorescence spectrometry and X-rays diffraction. In addition to the solubility in SBF, an in vivo pilot study assessed the dispersion of radioactive seeds implanted in rabbit muscle tissue. Four experiments were prepared to investigate the biological response in vitro, in which radioactive seeds were placed directly in contact with the cells in confluent culture flasks. The first two were done with seed's activity of 3.7 MBq (0.1 mCi) for the Sm-153 and 11.1 MBq (0.3 mCi) for Ho-166. There were no concerns with spatial positioning for seeds in those early experiments. The subsequent experiments were performed with activity ranging from 37 MBq (1 mCi) and 111 MBq (3 mCi) and with defined position of the seeds in the flask. The results showed the presence of halos with maximum diameter of 8 mm around the seeds where there was a drastic reduction in the number of viable cells as a result of the effects of β radiation. The calculation of dose deposited in water as well as the dose rate calculation of during handling of the seeds for an implant followed the methodology established by MIRD. These calculations found dose rates ranging from 7 to 19 Gy/h and integrated doses between 93 and 730 Gy, due to β radiation, for 6 half-lives of radioisotopes Sm-153 and Ho-166. The dose

  12. [Literature review of the dispersal of transgenes from genetically modified maize].

    Science.gov (United States)

    Ricroch, Agnès; Bergé, Jean Baptiste; Messéan, Antoine

    2009-10-01

    This article aims at reviewing the theoretical and experimental data published in 562 publications referring to genetically modified (GM) maize dispersal. Our choice was limited to this since in the European Union (EU), GM maize is the only GM crop currently grown commercially. The pollen dispersal of transgenic maize is due to two factors: (i) pollen-mediated gene flow; (ii) seed admixture during harvest and post-harvest processes. The pollen dispersal decreases rapidly with the distance from GM plots. Climatic and topographic factors and factors of relative density between GM and non-GM maize plots impact on the pollen dispersal. The combination of both isolation distance and flowering date between source plots and sink plots limits the adventitious presence of transgenes in non-GM plots. All publications we reviewed demonstrate that the EU 0.9% threshold is technically manageable if the measures of isolation distances as well as harvesting and post harvesting processes and fully synchronous flowering are implemented.

  13. Experimental Investigation of the Dietary Ecology of the Extinct Passenger Pigeon, Ectopistes migratorius

    Directory of Open Access Journals (Sweden)

    Ben J. Novak

    2018-03-01

    Full Text Available For tens of thousands of years, passenger pigeons (Ectopistes migratorius were a dominant member of eastern North American forest communities, with megaflocks comprising up to several billion individuals. The extinction of passenger pigeons in the early twentieth century undoubtedly influenced associated species and ecosystems as interactions stemming from the pigeons disappeared suddenly. Here, we strive to better understand what was probably one of the most significant of these interactions—that between passenger pigeons and seed bearing trees. Using the band-tailed pigeon (Patagioenas fasciata and the rock dove (Columba livia as physical and ecological proxies, we evaluated passenger pigeon dietary range and potential to disperse seeds. Our findings suggest that the passenger pigeon's dietary range, observed historically to be taxonomically broad, was constrained to certain seed sizes due to bill gape size. In addition, we conclude that the digestive process invariably destroyed consumed seeds but the potential for a nutrition/dispersal mutualism might still have existed via regurgitation and post-mortem release of crop contents. Our results highlight the range of ecological interactions that can be lost with species' extinction and the inherent challenge of understanding the consequences of those interactions.

  14. Nonrandom Composition of Flower Colors in a Plant Community: Mutually Different Co-Flowering Natives and Disturbance by Aliens

    Science.gov (United States)

    Makino, Takashi T.; Yokoyama, Jun

    2015-01-01

    When pollinators use flower color to locate food sources, a distinct color can serve as a reproductive barrier against co-flowering species. This anti-interference function of flower color may result in a community assembly of plant species displaying mutually different flower colors. However, such color dispersion is not ubiquitous, suggesting a variable selection across communities and existence of some opposing factors. We conducted a 30-week study in a plant community and measured the floral reflectances of 244 species. The reflectances were evaluated in insect color spaces (bees, swallowtails, and flies), and the dispersion was compared with random expectations. We found that co-existing colors were overdispersed for each analyzed pollinator type, and this overdispersion was statistically significant for bees. Furthermore, we showed that exclusion of 32 aliens from the analysis significantly increased the color dispersion of native flowers in every color space. This result indicated that aliens disturbed a native plant–pollinator network via similarly colored flowers. Our results demonstrate the masking effects of aliens in the detection of color dispersion of native flowers and that variations in pollinator vision yield different outcomes. Our results also support the hypothesis that co-flowering species are one of the drivers of color diversification and affect the community assembly. PMID:26650121

  15. Nonrandom Composition of Flower Colors in a Plant Community: Mutually Different Co-Flowering Natives and Disturbance by Aliens.

    Directory of Open Access Journals (Sweden)

    Takashi T Makino

    Full Text Available When pollinators use flower color to locate food sources, a distinct color can serve as a reproductive barrier against co-flowering species. This anti-interference function of flower color may result in a community assembly of plant species displaying mutually different flower colors. However, such color dispersion is not ubiquitous, suggesting a variable selection across communities and existence of some opposing factors. We conducted a 30-week study in a plant community and measured the floral reflectances of 244 species. The reflectances were evaluated in insect color spaces (bees, swallowtails, and flies, and the dispersion was compared with random expectations. We found that co-existing colors were overdispersed for each analyzed pollinator type, and this overdispersion was statistically significant for bees. Furthermore, we showed that exclusion of 32 aliens from the analysis significantly increased the color dispersion of native flowers in every color space. This result indicated that aliens disturbed a native plant-pollinator network via similarly colored flowers. Our results demonstrate the masking effects of aliens in the detection of color dispersion of native flowers and that variations in pollinator vision yield different outcomes. Our results also support the hypothesis that co-flowering species are one of the drivers of color diversification and affect the community assembly.

  16. Dispersion and current measurements

    International Nuclear Information System (INIS)

    Boelskifte, S.

    1986-04-01

    A model for the simulation of particle movements in water should incorporate the mutual distance dependent correlation. As long as reliable data are given accessible a model can be created of the dispersion in a given area from a statistical description of turbulence. Current measurements have been performed in an area north of the Swedish nuclear power plant Barsebaeck, and statistical time series analysis have made it possible to estimate multivariate autoregressive moving-average (ARMA) models for these data using the Box-Jenkins method. The correlation structure for the area has been investigated in detail. Transport and dispersion models for the marine environment are used in estimating doses to the population from the aquatic food chain. Some of these models are described with special emphasis on the time and length scales they cover. Furthermore, to illustrate the background of the simulation model, short introductuions are given to health physics, time series analysis, and turbulence theory. Analysis of the simulation model shows the relative importance of the different parameters. The model can be expanded to conditional simulation, where the current measurements are used directly to simulate the movement of one of the particles. Results from the model are also compared to results from a sampling of bioindicators (Fucus vesiculosus) along the Danish coast. The reliability of bioindicators in this kind of experiment is discussed. (author)

  17. (Mutual Security Mutual Affluence) Negative Factors = Sustained Stability: A Framework for Establishing Stability Between Like States

    Science.gov (United States)

    2017-03-31

    160-163. 2 The Concept of Mutually Assured Destruction (MAD) dates back to the post-WWFI em and the Cold War where the United States and Soviet Unions...United States. Following its defeat in W\\VH, Japan was in shambles. The bombing campaigns left nine million Japanese homeless and three million more...the United States, the Charlie Hebdo attacks in Paris in 2015, and the bombings in Istanbul in 2016. Michael Bamier, “From Mutual Assistance to

  18. Generalized Mutual Synchronization between Two Controlled Interdependent Networks

    Directory of Open Access Journals (Sweden)

    Quan Xu

    2014-01-01

    Full Text Available This paper mainly focuses on the generalized mutual synchronization between two controlled interdependent networks. First, we propose the general model of controlled interdependent networks A and B with time-varying internetwork delays coupling. Then, by constructing Lyapunov functions and utilizing adaptive control technique, some sufficient conditions are established to ensure that the mutual synchronization errors between the state variables of networks A and B can asymptotically converge to zero. Finally, two numerical examples are given to illustrate the effectiveness of the theoretical results and to explore potential application in future smart grid. The simulation results also show how interdependent topologies and internetwork coupling delays influence the mutual synchronizability, which help to design interdependent networks with optimal mutual synchronizability.

  19. Mutual proximity graphs for improved reachability in music recommendation.

    Science.gov (United States)

    Flexer, Arthur; Stevens, Jeff

    2018-01-01

    This paper is concerned with the impact of hubness, a general problem of machine learning in high-dimensional spaces, on a real-world music recommendation system based on visualisation of a k-nearest neighbour (knn) graph. Due to a problem of measuring distances in high dimensions, hub objects are recommended over and over again while anti-hubs are nonexistent in recommendation lists, resulting in poor reachability of the music catalogue. We present mutual proximity graphs, which are an alternative to knn and mutual knn graphs, and are able to avoid hub vertices having abnormally high connectivity. We show that mutual proximity graphs yield much better graph connectivity resulting in improved reachability compared to knn graphs, mutual knn graphs and mutual knn graphs enhanced with minimum spanning trees, while simultaneously reducing the negative effects of hubness.

  20. Diet quality modifies germination of Dichrostachys cinerea and Acacia nilotica seeds fed to ruminants

    CSIR Research Space (South Africa)

    Tjelele, J

    2014-07-01

    Full Text Available The pods of many woody plants form an important part of the diet of livestock during the dry season due to their high nutritive value. However, the dispersal of seeds that remain intact and can potentially germinate after excretion is of particular...

  1. The effect of fire on the dormancy break of annual legume seeds

    Directory of Open Access Journals (Sweden)

    Fabio Gresta

    2011-07-01

    Full Text Available Fire is a common phenomenon in the Mediterranean environment and strongly influences vegetal population dynamics through its impact on vegetation and the soil seed bank. Fire is able to break down the seed coat of hard-seeded legumes within the soil and trigger germination. To evaluate the effect of fire on the dormancy break in Medicago ciliaris, Medicago rugosa and Scorpiurus muricatus subsp. subvillosus, the seeds were placed at three different depths (surface, 25 mm and 50 mm and subjected to fires at two different intensities (high and low. As a control sample, a batch of seeds was buried at 25 mm for the duration of the trial and not subjected to fire. Soil temperatures during the fire were compared directly to stubble quantity and indirectly related to soil depth. The two Medicago species survived exposure to 90°C for a few minutes and displayed a significant increase in germination with exposure to high temperatures (over 70°C for several minutes. On the other hand, no germination occurred in Scorpiurus, irrespective of treatment. In conclusion, fire had a significant and positive effect in triggering germination of the Medicago species, but the dispersal strategies of these hard-seeded legumes are only partially interrupted by fire as a large number of seeds (>50% remained non-germinated in the soil.

  2. Irradiation effect on the seed vigor, SOD activity and MDA content in germinating seeds of yellow-seeded and black-seeded rape seed (Brassica napus L.)

    International Nuclear Information System (INIS)

    Han Jixiang; Hu Danhong; Liu Houli

    1993-01-01

    Seeds of a set of near-isogenic lines (Brassica napus L.) with different seed coat color from yellow to black were irradiated by 60 Co γ-rays of 150 krad. Seed vigor, superoxide dismutase (SOD) and malondialdehyde (MDA) in germinating seeds were analysed. In these characters, no significant difference between yellow-seeded lines (YLs) and black-seeded lines (BLs) showed before irradiation. But after irradiation, SOD activity in YLs was lower than that in BLs. While MDA content in YLs was obviously higher that that in DLs. As a result of irradiation, seed vigor of YLs was lower than that in BLs. these results indicated that the irradiation resistance of rape seed was related to the level of SOD as well as protective structure or substances in seed coat and that the radiosensitivity of YLs was higher than that of DLs

  3. Downside Risk Timing by Mutual Funds

    OpenAIRE

    Bodnaruk, Andriy; Chokaev, Bekhan; Simonov, Andrei

    2015-01-01

    We study whether mutual funds systematically manage downside risk of their portfolios in ways that improve their performance. We find that actively managed mutual funds on average possess positive downside risk timing ability. Funds investing in large-cap and value stocks have stronger downside risk timing skills. Managers adjust funds’ downside risk exposure in response to macroeconomic information. The economic value of downside risk timing is comparable to that of market timing.

  4. Performance of Mutual Funds In INDIA: 2000 - 2006.

    OpenAIRE

    Kabra, Krishna

    2006-01-01

    Numerous scholarly researches have been carried out to evaluate the performance of mutual funds. These researches may differ in time period but most studies conclude that mutual funds on average have failed to outperform the market and therefore the efficient market hypothesis holds good. This research is carried out to evaluate the performance of 20 surviving diversified equity growth mutual funds for the period of 6 years from July 2000 to June 2006. The data of the fund is collected on Mon...

  5. Seasonal asset allocation: Evidence from mutual fund flows

    OpenAIRE

    Kamstra, Mark J.; Kramer, Lisa A.; Levi, Maurice D.; Wermers, Russ

    2013-01-01

    Over the past 30 years, mutual funds have become the dominant vehicle through which individual investors prepare for retirement via defined contribution plans. Further, money market mutual funds, which hold $2.7 trillion as of September 2013, are now a major part of the cash economy in the U.S. Accordingly, the flow of money to and from different mutual fund categories (e.g., equities vs. money funds) increasingly reflects the sentiment or risk aversion of the general population. In this stud...

  6. Bright Lights and Questions: Using Mutual Interrogation

    Science.gov (United States)

    Adam, Aishikin; Alangui, Willy; Barton, Bill

    2010-01-01

    Mutual Interrogation is a research methodology for ethnomathematics proposed by Alangui in 2006 in an attempt to avoid the potential inequality set up when a restricted cultural practice is viewed through the lens of the near-universal and highly developed research domain of mathematics. Using three significant examples of mutual interrogation in…

  7. Mutual inactivation of Notch receptors and ligands facilitates developmental patterning.

    Directory of Open Access Journals (Sweden)

    David Sprinzak

    2011-06-01

    Full Text Available Developmental patterning requires juxtacrine signaling in order to tightly coordinate the fates of neighboring cells. Recent work has shown that Notch and Delta, the canonical metazoan juxtacrine signaling receptor and ligand, mutually inactivate each other in the same cell. This cis-interaction generates mutually exclusive sending and receiving states in individual cells. It generally remains unclear, however, how this mutual inactivation and the resulting switching behavior can impact developmental patterning circuits. Here we address this question using mathematical modeling in the context of two canonical pattern formation processes: boundary formation and lateral inhibition. For boundary formation, in a model motivated by Drosophila wing vein patterning, we find that mutual inactivation allows sharp boundary formation across a broader range of parameters than models lacking mutual inactivation. This model with mutual inactivation also exhibits robustness to correlated gene expression perturbations. For lateral inhibition, we find that mutual inactivation speeds up patterning dynamics, relieves the need for cooperative regulatory interactions, and expands the range of parameter values that permit pattern formation, compared to canonical models. Furthermore, mutual inactivation enables a simple lateral inhibition circuit architecture which requires only a single downstream regulatory step. Both model systems show how mutual inactivation can facilitate robust fine-grained patterning processes that would be difficult to implement without it, by encoding a difference-promoting feedback within the signaling system itself. Together, these results provide a framework for analysis of more complex Notch-dependent developmental systems.

  8. FRUIT AND SEED BIOMETRY AND DETERMINATION OF THE WATER ABSORPTION CURVE OF SESBANIA VIRGATA (CAV. PERS.

    Directory of Open Access Journals (Sweden)

    S Acchile

    2017-10-01

    Full Text Available The species Sesbania virgata (Cav. Pers., Fabaceae popularly known as Sesbania or Feijão do Mato, presents potential in the use in areas of afforestation and reforestation forests riparian and degraded areas. The aim of this study was to characterize the biometric of fruits and seeds and determine the germination pattern of the sesbânia seeds. The biometry of the seeds and fruits were established through the characterization of 250 fruits and 500 seeds, which were distributed in frequency classes through position, dispersion and normality measurements. The weight of one thousand seeds (PMS was determined using eight sub samples of the 100 seeds. For to study of the water absorption curve of the seeds were used two replicates of 100 seeds, it weighed in 32 intervals. In this sense, the biometric fruits aspects of S. virgata presented average values for length, width, thickness, weight and number of seeds per fruit of 5.87 cm, 0.78 cm, 0.58 cm, 0.85 g and 5 units, respectively. In relation to the seeds, the average length, width, thickness and seed weight were 0.623 cm; 0.439 cm; 0.316 cm and 0.075 g, respectively. The water absorption of S. virgata seed imbibition presented triphasic pattern, resembling several species of the same family.

  9. mutual participation in the health worker-patient relationship

    African Journals Online (AJOL)

    Medunsa) ... Keywords: mutual participation, health worker-patient relationship, decision ... The importance of a mutual participatory model in medical care and decision ... workers become aware of differences in opinion or in the balance of power, ...

  10. Defined Contribution Pension Plans: Mutual Fund Asset Allocation Changes

    OpenAIRE

    Clemens Sialm; Laura Starks; Hanjiang Zhang

    2015-01-01

    In this paper we compare changes in asset allocations between mutual funds held in defined contribution pension plans and funds held by other investors. We investigate how flows into equity and fixed income mutual funds depend on macroeconomic conditions. We find that defined contribution plans react more sensitively to these conditions, suggesting effects on mutual fund managers and other investors.

  11. Performance of Mutual Funds in India: (2002-2006)

    OpenAIRE

    Saboo, Manish

    2006-01-01

    There has been many studies in the past on performance of Mutual Funds in comparison to the market. These studies might differ in time and the market under study but most of them concluded that on an average, Mutual Funds have failed to outperform the market and thus the Efficient Market Hypothesis holds good. This research was based on performance of 25 mutual funds for a period of almost 5 years on monthly basis. Funds were evaluated using measures like Sharpe ratio, Treynor ratio, Jense...

  12. Habitat fragmentation reduces grassland connectivity for both short-distance and long-distance wind-dispersed forbs

    NARCIS (Netherlands)

    Soons, M.B.; Messelink, J.H.; Jongejans, E.; Heil, G.W.

    2005-01-01

    1 Although habitat loss and fragmentation are assumed to threaten the regional survival of plant species, their effects on regional species dynamics via seed dispersal and colonization have rarely been quantified. 2 We assessed the impact of habitat loss and fragmentation on the connectivity, and

  13. ABA crosstalk with ethylene and nitric oxide in seed dormancy and germination

    Directory of Open Access Journals (Sweden)

    Erwann eArc

    2013-03-01

    Full Text Available Dormancy is an adaptive trait that enables seed germination to coincide with favorable environmental conditions. It has been clearly demonstrated that dormancy is induced by abscisic acid (ABA during seed development on the mother plant. After seed dispersal, germination is preceded by a decline in ABA in imbibed seeds, which results from ABA catabolism through 8’-hydroxylation. The hormonal balance between ABA and gibberellins (GAs has been shown to act as an integrator of environmental cues to maintain dormancy or activate germination. The interplay of ABA with other endogenous signals is however less documented. In numerous species, ethylene counteracts ABA signaling pathways and induces germination. In Brassicaceae seeds, ethylene prevents the inhibitory effects of ABA on endosperm cap weakening, thereby facilitating endosperm rupture and radicle emergence. Moreover, enhanced seed dormancy in Arabidopsis ethylene-insensitive mutants results from greater ABA sensitivity. Conversely, ABA limits ethylene action by down-regulating its biosynthesis. Nitric oxide (NO has been proposed as a common actor in the ABA and ethylene crosstalk in seed. Indeed, convergent evidence indicates that NO is produced rapidly after seed imbibition and promotes germination by inducing the expression of the ABA 8’-hydroxylase gene, CYP707A2, and stimulating ethylene production. The role of NO and other nitrogen-containing compounds, such as nitrate, in seed dormancy breakage and germination stimulation has been reported in several species. This review will describe our current knowledge of ABA crosstalk with ethylene and NO, both volatile compounds that have been shown to counteract ABA action in seeds and to improve dormancy release and germination.

  14. Organic leek seed production - securing seed quality

    DEFF Research Database (Denmark)

    Deleuran, Lise Christina; Boelt, Birte

    2011-01-01

    To maintain integrity in organic farming, availability of organically produced GM-free seed of varieties adapted to organic production systems is of vital impor-tance. Despite recent achievements, organic seed supply for a number of vegetable species is insufficient. Still, in many countries...... seeds. Tunnel production is a means of securing seed of high genetic purity and quality, and organic leek (Allium porrum L.) seed production was tested in tunnels in Denmark. The present trial focused on steckling size and in all years large stecklings had a positive effect on both seed yield...

  15. Organic Leek Seed Production - Securing Seed Quality

    DEFF Research Database (Denmark)

    Deleuran, L C; Boelt, B

    2011-01-01

    To maintain integrity in organic farming, availability of organically produced GM-free seed of varieties adapted to organic production systems is of vital impor-tance. Despite recent achievements, organic seed supply for a number of vegetable species is insufficient. Still, in many countries...... seeds. Tunnel production is a means of securing seed of high genetic purity and quality, and organic leek (Allium porrum L.) seed production was tested in tunnels in Denmark. The present trial focused on steckling size and in all years large stecklings had a positive effect on both seed yield...

  16. High temperatures result in smaller nurseries which lower reproduction of pollinators and parasites in a brood site pollination mutualism.

    Science.gov (United States)

    Krishnan, Anusha; Pramanik, Gautam Kumar; Revadi, Santosh V; Venkateswaran, Vignesh; Borges, Renee M

    2014-01-01

    In a nursery pollination mutualism, we asked whether environmental factors affected reproduction of mutualistic pollinators, non-mutualistic parasites and seed production via seasonal changes in plant traits such as inflorescence size and within-tree reproductive phenology. We examined seasonal variation in reproduction in Ficus racemosa community members that utilise enclosed inflorescences called syconia as nurseries. Temperature, relative humidity and rainfall defined four seasons: winter; hot days, cold nights; summer and wet seasons. Syconium volumes were highest in winter and lowest in summer, and affected syconium contents positively across all seasons. Greater transpiration from the nurseries was possibly responsible for smaller syconia in summer. The 3-5°C increase in mean temperatures between the cooler seasons and summer reduced fig wasp reproduction and increased seed production nearly two-fold. Yet, seed and pollinator progeny production were never negatively related in any season confirming the mutualistic fig-pollinator association across seasons. Non-pollinator parasites affected seed production negatively in some seasons, but had a surprisingly positive relationship with pollinators in most seasons. While within-tree reproductive phenology did not vary across seasons, its effect on syconium inhabitants varied with season. In all seasons, within-tree reproductive asynchrony affected parasite reproduction negatively, whereas it had a positive effect on pollinator reproduction in winter and a negative effect in summer. Seasonally variable syconium volumes probably caused the differential effect of within-tree reproductive phenology on pollinator reproduction. Within-tree reproductive asynchrony itself was positively affected by intra-tree variation in syconium contents and volume, creating a unique feedback loop which varied across seasons. Therefore, nursery size affected fig wasp reproduction, seed production and within-tree reproductive phenology

  17. Mutual information against correlations in binary communication channels.

    Science.gov (United States)

    Pregowska, Agnieszka; Szczepanski, Janusz; Wajnryb, Eligiusz

    2015-05-19

    Explaining how the brain processing is so fast remains an open problem (van Hemmen JL, Sejnowski T., 2004). Thus, the analysis of neural transmission (Shannon CE, Weaver W., 1963) processes basically focuses on searching for effective encoding and decoding schemes. According to the Shannon fundamental theorem, mutual information plays a crucial role in characterizing the efficiency of communication channels. It is well known that this efficiency is determined by the channel capacity that is already the maximal mutual information between input and output signals. On the other hand, intuitively speaking, when input and output signals are more correlated, the transmission should be more efficient. A natural question arises about the relation between mutual information and correlation. We analyze the relation between these quantities using the binary representation of signals, which is the most common approach taken in studying neuronal processes of the brain. We present binary communication channels for which mutual information and correlation coefficients behave differently both quantitatively and qualitatively. Despite this difference in behavior, we show that the noncorrelation of binary signals implies their independence, in contrast to the case for general types of signals. Our research shows that the mutual information cannot be replaced by sheer correlations. Our results indicate that neuronal encoding has more complicated nature which cannot be captured by straightforward correlations between input and output signals once the mutual information takes into account the structure and patterns of the signals.

  18. Performance of Mutual Funds in India 2003-2008

    OpenAIRE

    Raizada, Shantanu

    2008-01-01

    Many studies have been conducted in the past on the performance of Mutual Funds in comparison to the market index. These studies may differ in their time period, but most of them concluded that on an average the Mutual Funds failed to outperform the market thus the Efficient Market Hypothesis holds good. This research was based on the performance of 20 open ended equity diversified growth Mutual Funds for a period of 5 years from April 2003 to March 2008 and was compared to the BSE 500. Funds...

  19. Controlled mutual quantum entity authentication using entanglement swapping

    International Nuclear Information System (INIS)

    Kang, Min-Sung; Hong, Chang-Ho; Heo, Jino; Lim, Jong-In; Yang, Hyung-Jin

    2015-01-01

    In this paper, we suggest a controlled mutual quantum entity authentication protocol by which two users mutually certify each other on a quantum network using a sequence of Greenberger–Horne–Zeilinger (GHZ)-like states. Unlike existing unidirectional quantum entity authentication, our protocol enables mutual quantum entity authentication utilizing entanglement swapping; moreover, it allows the managing trusted center (TC) or trusted third party (TTP) to effectively control the certification of two users using the nature of the GHZ-like state. We will also analyze the security of the protocol and quantum channel. (paper)

  20. Freedom and imperative: mutual care between older spouses with physical disabilities.

    Science.gov (United States)

    Torgé, Cristina Joy

    2014-05-01

    This article explores mutual caregiving between older spouses aging with physical disabilities. Nine older couples, where both partners had lived long lives with physical disabilities, were interviewed as dyads about mutual caregiving. The couples not only had access to different kinds and degrees of formal support but also provided mutual care to each other in a variety of ways. Interview coding using grounded theory led to two overarching categories from which motivation for mutual caregiving could be understood. These categories were Mutual care as freedom and Mutual care as imperative. The results extend understanding about how older couples with disabilities attached meaning to their mutual caregiving, and why mutual care was sometimes preferable, despite the availability of other sources of help and despite practical difficulties of providing this help. These findings suggest that health care professionals need to be sensitive to the dynamics of the couple relationship and carefully explore the couple's preferences for how formal support can best be provided in ways that honor and sustain the integrity of the couple relationship.

  1. Out of Africa:Miocene Dispersal, Vicariance, and Extinction within Hyacinthaceae Subfamily Urgineoideae

    Institute of Scientific and Technical Information of China (English)

    Syed Shujait Ali; Martin Pfosser; Wolfgang Wetschnig; Mario MartnezAzorn; Manuel B. Crespo; Yan Yu

    2013-01-01

    Disjunct distribution patterns in plant lineages are usually explained according to three hypotheses:vicariance, geodispersal, and long-distance dispersal. The role of these hypotheses is tested in Urgineoideae (Hyacinthaceae), a subfamily disjunctly distributed in Africa, Madagascar, India, and the Mediterranean region. The potential ancestral range, dispersal routes, and factors responsible for the current distribution in Urgineoideae are investigated using divergence time estimations. Urgineoideae originated in Southern Africa approximately 48.9 Mya. Two independent dispersal events in the Western Mediterranean region possibly occurred during Early Oligocene and Miocene (29.9-8.5 Mya) via Eastern and Northwestern Africa. A dispersal from Northwestern Africa to India could have occurred between 16.3 and 7.6 Mya. Vicariance and extinction events occurred approximately 21.6 Mya. Colonization of Madagascar occurred between 30.6 and 16.6 Mya, after a single transoceanic dispersal event from Southern Africa. The current disjunct distributions of Urgineoideae are not satisfactorily explained by Gondwana fragmentation or dispersal via boreotropical forests, due to the younger divergence time estimates. The flattened winged seeds of Urgineoideae could have played an important role in long-distance dispersal by strong winds and big storms, whereas geodispersal could have also occurred from Southern Africa to Asia and the Mediterranean region via the so-called arid and high-altitude corridors.

  2. Management of Protected Areas and Its Effect on an Ecosystem Function: Removal of Prosopis flexuosa Seeds by Mammals in Argentinian Drylands

    Science.gov (United States)

    Campos, Valeria E.; Miguel, Florencia; Cona, Mónica I.

    2016-01-01

    The ecological function of animal seed dispersal depends on species interactions and can be affected by drivers such as the management interventions applied to protected areas. This study was conducted in two protected areas in the Monte Desert: a fenced reserve with grazing exclusion and absence of large native mammals (the Man and Biosphere Ñacuñán Reserve; FR) and an unfenced reserve with low densities of large native and domestic animals (Ischigualasto Park; UFR). The study focuses on Prosopis flexuosa seed removal by different functional mammal groups: “seed predators”, “scatter-hoarders”, and “opportunistic frugivores”. Under both interventions, the relative contribution to seed removal by different functional mammal groups was assessed, as well as how these groups respond to habitat heterogeneity (i.e. vegetation structure) at different spatial scales. Camera traps were used to identify mammal species removing P. flexuosa seeds and to quantify seed removal; remote sensing data helped analyze habitat heterogeneity. In the FR, the major fruit removers were a seed predator (Graomys griseoflavus) and a scatter-hoarder (Microcavia asutralis). In the UFR, the main seed removers were the opportunistic frugivores (Lycalopex griseus and Dolichotis patagonum), who removed more seeds than the seed predator in the FR. The FR shows higher habitat homogeneity than the UFR, and functional groups respond differently to habitat heterogeneity at different spatial scales. In the FR, because large herbivores are locally extinct (e.g. Lama guanicoe) and domestic herbivores are excluded, important functions of large herbivores are missing, such as the maintenance of habitat heterogeneity, which provides habitats for medium-sized opportunistic frugivores with consequent improvement of quality and quantity of seed dispersal services. In the UFR, with low densities of large herbivores, probably one important ecosystem function this group performs is to increase

  3. Management of Protected Areas and Its Effect on an Ecosystem Function: Removal of Prosopis flexuosa Seeds by Mammals in Argentinian Drylands.

    Directory of Open Access Journals (Sweden)

    Claudia M Campos

    Full Text Available The ecological function of animal seed dispersal depends on species interactions and can be affected by drivers such as the management interventions applied to protected areas. This study was conducted in two protected areas in the Monte Desert: a fenced reserve with grazing exclusion and absence of large native mammals (the Man and Biosphere Ñacuñán Reserve; FR and an unfenced reserve with low densities of large native and domestic animals (Ischigualasto Park; UFR. The study focuses on Prosopis flexuosa seed removal by different functional mammal groups: "seed predators", "scatter-hoarders", and "opportunistic frugivores". Under both interventions, the relative contribution to seed removal by different functional mammal groups was assessed, as well as how these groups respond to habitat heterogeneity (i.e. vegetation structure at different spatial scales. Camera traps were used to identify mammal species removing P. flexuosa seeds and to quantify seed removal; remote sensing data helped analyze habitat heterogeneity. In the FR, the major fruit removers were a seed predator (Graomys griseoflavus and a scatter-hoarder (Microcavia asutralis. In the UFR, the main seed removers were the opportunistic frugivores (Lycalopex griseus and Dolichotis patagonum, who removed more seeds than the seed predator in the FR. The FR shows higher habitat homogeneity than the UFR, and functional groups respond differently to habitat heterogeneity at different spatial scales. In the FR, because large herbivores are locally extinct (e.g. Lama guanicoe and domestic herbivores are excluded, important functions of large herbivores are missing, such as the maintenance of habitat heterogeneity, which provides habitats for medium-sized opportunistic frugivores with consequent improvement of quality and quantity of seed dispersal services. In the UFR, with low densities of large herbivores, probably one important ecosystem function this group performs is to increase

  4. Barriers to seed and seedling survival of once-common Hawaiian palms: the role of invasive rats and ungulates.

    Science.gov (United States)

    Shiels, Aaron B; Drake, Donald R

    2015-05-27

    Mammalian herbivores can limit plant recruitment and affect forest composition. Loulu palms (Pritchardia spp.) once dominated many lowland ecosystems in Hawai'i, and non-native rats (Rattus spp.), ungulates (e.g. pigs Sus scrofa, goats Capra hircus) and humans have been proposed as major causes of their decline. In lowland wet forest, we experimentally determined the vulnerability of seeds and seedlings of two species of Pritchardia, P. maideniana and P. hillebrandii, by measuring their removal by introduced vertebrates; we also used motion-sensing cameras to identify the animals responsible for Pritchardia removal. We assessed potential seed dispersal of P. maideniana by spool-and-line tracking, and conducted captive-feeding trials with R. rattus and seeds and seedlings of both Pritchardia species. Seed removal from the forest floor occurred rapidly for both species: >50 % of Pritchardia seeds were removed from the vertebrate-accessible stations within 6 days and >80 % were removed within 22 days. Although rats and pigs were both common to the study area, motion-sensing cameras detected only rats (probably R. rattus) removing Pritchardia seeds from the forest floor. Captive-feeding trials and spool-and-line tracking revealed that vertebrate seed dispersal is rare; rats moved seeds up to 8 m upon collection and subsequently destroyed them (100 % mortality in 24-48 h in captivity). Surprisingly, seedlings did not suffer vertebrate damage in field trials, and although rats damaged seedlings in captivity, they rarely consumed them. Our findings are consistent with the hypothesis generated from palaeoecological studies, indicating that introduced rats may have assisted in the demise of native insular palm forests. These findings also imply that the seed stage of species in this Pacific genus is particularly vulnerable to rats; therefore, future conservation efforts involving Pritchardia should prioritize the reduction of rat predation on the plant recruitment stages

  5. Mutually unbiased bases

    Indian Academy of Sciences (India)

    Mutually unbiased bases play an important role in quantum cryptography [2] and in the optimal determination of the density operator of an ensemble [3,4]. A density operator ρ in N-dimensions depends on N2 1 real quantities. With the help of MUB's, any such density operator can be encoded, in an optimal way, in terms of ...

  6. Exotic mammals disperse exotic fungi that promote invasion by exotic trees.

    Science.gov (United States)

    Nuñez, Martin A; Hayward, Jeremy; Horton, Thomas R; Amico, Guillermo C; Dimarco, Romina D; Barrios-Garcia, M Noelia; Simberloff, Daniel

    2013-01-01

    Biological invasions are often complex phenomena because many factors influence their outcome. One key aspect is how non-natives interact with the local biota. Interaction with local species may be especially important for exotic species that require an obligatory mutualist, such as Pinaceae species that need ectomycorrhizal (EM) fungi. EM fungi and seeds of Pinaceae disperse independently, so they may use different vectors. We studied the role of exotic mammals as dispersal agents of EM fungi on Isla Victoria, Argentina, where many Pinaceae species have been introduced. Only a few of these tree species have become invasive, and they are found in high densities only near plantations, partly because these Pinaceae trees lack proper EM fungi when their seeds land far from plantations. Native mammals (a dwarf deer and rodents) are rare around plantations and do not appear to play a role in these invasions. With greenhouse experiments using animal feces as inoculum, plus observational and molecular studies, we found that wild boar and deer, both non-native, are dispersing EM fungi. Approximately 30% of the Pinaceae seedlings growing with feces of wild boar and 15% of the seedlings growing with deer feces were colonized by non-native EM fungi. Seedlings growing in control pots were not colonized by EM fungi. We found a low diversity of fungi colonizing the seedlings, with the hypogeous Rhizopogon as the most abundant genus. Wild boar, a recent introduction to the island, appear to be the main animal dispersing the fungi and may be playing a key role in facilitating the invasion of pine trees and even triggering their spread. These results show that interactions among non-natives help explain pine invasions in our study area.

  7. Endozoochory of seeds and invertebrates by migratory waterbirds in Oklahoma, USA

    Science.gov (United States)

    Green, Andy J.; Frisch, Dagmar; Michot, Thomas C.; Allain, Larry K.; Barrow, Wylie C.

    2013-01-01

    Given their abundance and migratory behavior, waterbirds have major potential for dispersing plants and invertebrates within North America, yet their role as vectors remains poorly understood. We investigated the numbers and types of invertebrates and seeds within freshly collected faecal samples (n = 22) of migratory dabbling ducks and shorebirds in November 2008 in two parts of Lake Texoma in southern Oklahoma. Killdeer Charadrius vociferus were transporting a higher number and diversity of both plants and invertebrates than the green-winged teal Anas carolinensis. Ten plant taxa and six invertebrate taxa were identified to at least genus level, although viability was not confirmed for most of these taxa. Bryozoan statoblasts (from four species not previously recorded from Oklahoma) were especially abundant in killdeer faeces, while the ostracod Candona simpsoni was detected as a live adult in torpor in the teal faeces. Cyperaceae and Juncaceae were the most abundant plant families represented and Cyperus strigosus seeds germinated after extraction from killdeer faeces. This snapshot study underlines the importance of waterbirds as vectors of passive dispersal of many organisms and the need for more research in this discipline.

  8. Market timing and selectivity performance of mutual funds in Ghana

    Directory of Open Access Journals (Sweden)

    Abubakar Musah

    2014-07-01

    Full Text Available The growing interest in mutual funds in Ghana has been tremendous over the last decade as evidenced by the continuous increases in number and total funds under management. However, no empirical work has been done on the selectivity and timing ability of the mutual fund managers. Using monthly returns data hand-collected from the reports of the mutual fund managers for the period January 2007-December 2012, this paper examines the market timing and selectivity ability of mutual fund managers in Ghana using the classic Treynor-Mazuy (1966 model and Henriksson- Merton (1981 model. The results suggest that, in general mutual fund managers in Ghana are not able to effectively select stocks and also are not able to predict both the magnitude and direction of future market returns. More specifically, all of the sample mutual fund managers attain significant negative selectivity coefficients and also most of them attain insignificant negative timing coefficients.

  9. The effect of fire on the dormancy break of three annual legume seeds

    Directory of Open Access Journals (Sweden)

    Fabio Gresta

    2011-07-01

    Full Text Available Fire is a common phenomenon in the Mediterranean environment and strongly influences vegetal population dynamics through its impact on vegetation and the soil seed bank. Fire is able to break down the seed coat of hard-seeded legumes within the soil and trigger germination. To evaluate the effect of fire on the dormancy break in Medicago ciliaris, Medicago rugosa and Scorpiurus muricatus subsp. subvillosus, the seeds were placed at three different depths (surface, 25 mm and 50 mm and subjected to fires at two different intensities (high and low. As a control sample, a batch of seeds was buried at 25 mm for the duration of the trial and not subjected to fire. Soil temperatures during the fire were compared directly to stubble quantity and indirectly related to soil depth. The two Medicago species survived exposure to 90°C for a few minutes and displayed a significant increase in germination with exposure to high temperatures (over 70°C for several minutes. On the other hand, no germination occurred in Scorpiurus, irrespective of treatment. In conclusion, fire had a significant and positive effect in triggering germination of the Medicago species, but the dispersal strategies of these hard-seeded legumes are only partially interrupted by fire as a large number of seeds (>50% remained non-germinated in the soil.

  10. 24 CFR 203.420 - Nature of Mutual Mortgage Insurance Fund.

    Science.gov (United States)

    2010-04-01

    ... 24 Housing and Urban Development 2 2010-04-01 2010-04-01 false Nature of Mutual Mortgage Insurance Fund. 203.420 Section 203.420 Housing and Urban Development Regulations Relating to Housing and Urban... and Distributive Shares § 203.420 Nature of Mutual Mortgage Insurance Fund. The Mutual Mortgage...

  11. Mutuality in Mother-Child Interactions in an Antillean Intervention Group

    Science.gov (United States)

    Boomstra, Nienke W.; van Dijk, Marijn W. G.; van Geert, Paul L. C.

    2016-01-01

    This article describes a study on mutuality in mother-child interaction during reading and playing sessions. Within mother-child interaction, mutuality is seen as important in language acquisition. The study was executed within a group of Netherlands Antillean mother-child dyads who participated in an intervention programme. Mutuality was…

  12. Seed-borne pathogens and electrical conductivity of soybean seeds

    Directory of Open Access Journals (Sweden)

    Adriana Luiza Wain-Tassi

    2012-02-01

    Full Text Available Adequate procedures to evaluate seed vigor are important. Regarding the electrical conductivity test (EC, the interference in the test results caused by seed-borne pathogens has not been clarified. This research was carried out to study the influence of Phomopsis sojae (Leh. and Colletotrichum dematium (Pers. ex Fr. Grove var. truncata (Schw. Arx. fungi on EC results. Soybean seeds (Glycine max L. were inoculated with those fungi using potato, agar and dextrose (PDA medium with manitol (-1.0 MPa and incubated for 20 h at 25 °C. The colony diameter, index of mycelial growth, seed water content, occurrence of seed-borne pathogens, physiological potential of the seeds, measured by germination and vigor tests (seed germination index, cold test, accelerated aging and electrical conductivity, and seedling field emergence were determined. The contents of K+, Ca2+, and Mg2+ in the seed and in the soaking solution were also determined. A complete 2 × 4 factorial design with two seed sizes (5.5 and 6.5 mm and four treatments (control, seeds incubated without fungi, seeds incubated with Phomopsis and seeds incubated with Colletotrichum were used with eight (5.5 mm large seeds and six (6.5 mm large seeds replications. All seeds submitted to PDA medium had their germination reduced in comparison to the control seeds. This reduction was also observed when seed vigor and leached ions were considered. The presence of Phomopsis sojae fungus in soybean seed samples submitted to the EC test may be the cause of misleading results.

  13. Pine invasions in treeless environments: dispersal overruns microsite heterogeneity.

    Science.gov (United States)

    Pauchard, Aníbal; Escudero, Adrián; García, Rafael A; de la Cruz, Marcelino; Langdon, Bárbara; Cavieres, Lohengrin A; Esquivel, Jocelyn

    2016-01-01

    Understanding biological invasions patterns and mechanisms is highly needed for forecasting and managing these processes and their negative impacts. At small scales, ecological processes driving plant invasions are expected to produce a spatially explicit pattern driven by propagule pressure and local ground heterogeneity. Our aim was to determine the interplay between the intensity of seed rain, using distance to a mature plantation as a proxy, and microsite heterogeneity in the spreading of Pinus contorta in the treeless Patagonian steppe. Three one-hectare plots were located under different degrees of P. contorta invasion (Coyhaique Alto, 45° 30'S and 71° 42'W). We fitted three types of inhomogeneous Poisson models to each pine plot in an attempt for describing the observed pattern as accurately as possible: the "dispersal" models, "local ground heterogeneity" models, and "combined" models, using both types of covariates. To include the temporal axis in the invasion process, we analyzed both the pattern of young and old recruits and also of all recruits together. As hypothesized, the spatial patterns of recruited pines showed coarse scale heterogeneity. Early pine invasion spatial patterns in our Patagonian steppe site is not different from expectations of inhomogeneous Poisson processes taking into consideration a linear and negative dependency of pine recruit intensity on the distance to afforestations. Models including ground-cover predictors were able to describe the point pattern process only in a couple of cases but never better than dispersal models. This finding concurs with the idea that early invasions depend more on seed pressure than on the biotic and abiotic relationships seed and seedlings establish at the microsite scale. Our results show that without a timely and active management, P. contorta will invade the Patagonian steppe independently of the local ground-cover conditions.

  14. Modelling nutritional mutualisms: challenges and opportunities for data integration.

    Science.gov (United States)

    Clark, Teresa J; Friel, Colleen A; Grman, Emily; Shachar-Hill, Yair; Friesen, Maren L

    2017-09-01

    Nutritional mutualisms are ancient, widespread, and profoundly influential in biological communities and ecosystems. Although much is known about these interactions, comprehensive answers to fundamental questions, such as how resource availability and structured interactions influence mutualism persistence, are still lacking. Mathematical modelling of nutritional mutualisms has great potential to facilitate the search for comprehensive answers to these and other fundamental questions by connecting the physiological and genomic underpinnings of mutualisms with ecological and evolutionary processes. In particular, when integrated with empirical data, models enable understanding of underlying mechanisms and generalisation of principles beyond the particulars of a given system. Here, we demonstrate how mathematical models can be integrated with data to address questions of mutualism persistence at four biological scales: cell, individual, population, and community. We highlight select studies where data has been or could be integrated with models to either inform model structure or test model predictions. We also point out opportunities to increase model rigour through tighter integration with data, and describe areas in which data is urgently needed. We focus on plant-microbe systems, for which a wealth of empirical data is available, but the principles and approaches can be generally applied to any nutritional mutualism. © 2017 John Wiley & Sons Ltd/CNRS.

  15. Distribution and dispersal of Xylaria endophytes in two tree species in Puerto Rico

    Science.gov (United States)

    P. Bayman; D. J. Lodge; P. Angulo-Sandoval; Z. Baez-Ortiz

    1998-01-01

    Xylaria species are common endophytes in tropical plants. It is not known, however, whether transmission of Xylaria occurs horizontally or vertically, whether individual Xylaria strains have wide host ranges or are host-specific, or how they are dispersed. We compared frequency of Xylaria endophytes in leaves and seeds of two tree species in Puerto Rico, Casuarina...

  16. Indirect control and power in mutual control structures

    NARCIS (Netherlands)

    Karos, D.; Peters, H.J.M.

    2013-01-01

    In a mutual control structure agents exercise control over each other. Typical examples occur in the area of corporate governance: firms and investment companies exercise mutual control, in particular by owning each others’ stocks. In this paper we formulate a general model for such situations.

  17. Tax-Efficient Asset Management: Evidence from Equity Mutual Funds

    OpenAIRE

    Clemens Sialm; Hanjiang Zhang

    2015-01-01

    Investment taxes have a substantial impact on the performance of taxable mutual fund investors. Mutual funds can reduce the tax burdens of their shareholders by avoiding securities that are heavily taxed and by avoiding realizing capital gains that trigger higher tax burdens to the funds’ investors. Such tax avoidance strategies constrain the investment opportunities of the mutual funds and might reduce their before-tax performance. Our paper empirically investigates the costs and benefits of...

  18. The Profile of a Polish Mutual Fund Manager

    Directory of Open Access Journals (Sweden)

    Dariusz Filip

    2018-05-01

    Full Text Available Aim/purpose - The purpose of this paper is to identify the characteristics that are typical of mutual fund managers. Design/methodology/approach - The study concentrates on a set of socio-demographic data, such as: age, gender, education, experience, and professional qualifications of 336 portfolio managers. The applied research strategy relies on an analysis concerning a set of statistical metrics describing the population under examination. Findings - The average Polish fund manager is a 37-year-old man, a holder of a stock-broker or investment adviser license. He obtained the authorization from the Polish Financial Supervision Authority (KNF a few years after graduating from the Warsaw School of Economics (SGH. He has 11 years' experience in financial markets and 7 years' experience in the mutual fund industry. Research implications/limitations - The identification of managerial characteristics for the purpose of creating a profile of a Polish mutual fund manager will provide an important basis for further surveys and analyses aimed to evaluate the effectiveness of mutual funds. Originality/value/contribution - There are no investigations within the discussed area in Polish studies. Therefore, the identification of the characteristics that are typical of mutual fund managers will make a contribution to the finance literature.(original abstract

  19. New fossil seeds of Eurya (Theaceae from East Asia and their paleobiogeographic implications

    Directory of Open Access Journals (Sweden)

    Hai Zhu

    2016-06-01

    Full Text Available Eurya has an excellent fossil record in Europe, but it has only a few fossil occurrences in East Asia though this vast area houses the highest modern diversity of the genus. In this study, three-dimensionally preserved fossil seeds of Eurya stigmosa (Ludwig Mai from the late Pliocene of northwestern Yunnan, southwestern China are described. The seeds are compressed and flattened, slightly campylotropous, and nearly circular to slightly angular in shape. The surface of the seeds is sculptured by a distinctive foveolate pattern, consisting of funnel-shaped and finely pitted cells. Each seed valve contains a reniform or horseshoe-shaped embryo cavity, a characteristic condyle structure and an internal raphe. These fossil seeds represent one of the few fossil records of Eurya in East Asia. This new finding therefore largely extends the distributional ranges of Eurya during Neogene. Fossil records summarized here show that Eurya persisted in Europe until the early Pleistocene, but disappeared thereafter. The genus might have first appeared in East Asia no later than the late Oligocene, and dispersed widely in regions such as Japan, Nepal, and southwestern China.

  20. Bio-Derived Hierarchical 3D Architecture from Seeds for Supercapacitor Application

    Science.gov (United States)

    Intawin, Pratthana; Sayed, Farheen N.; Pengpat, Kamonpan; Joyner, Jarin; Tiwary, Chandra Sekhar; Ajayan, Pulickel M.

    2017-09-01

    The generation and storage of green energy (energy from abundant and nonfossil) is important for a sustainable and clean future. The electrode material in a supercapacitor is a major component. The properties of these materials depend on its inherent architecture and composition. Here, we have chosen sunflower seeds and pumpkin seeds with a completely different structure to obtain a carbonaceous product. The product obtained from sunflower seed carbon is a three-dimensional hierarchical macroporous carbon (SSC) composed of many granular nanocrystals of potassium magnesium phosphate dispersed in a matrix. Contrary to this, carbon from pumpkin seeds (PSC) is revealed to be a more rigid structure, with no porous or ordered morphology. The electrochemical supercapacitive behavior was assessed by cyclic voltammetry and galvanostatic charge-discharge tests. Electrochemical measurements showed that the SSC shows a high specific capacitance of 24.9 Fg-1 as compared with that obtained (2.46 Fg-1) for PSC with a cycling efficiency of 87% and 89%, respectively. On high-temperature cycling for 500 charge-discharge cycles at 0.1 Ag-1, an improved cycling efficiency of 100% and 98% for SSC and PSC, respectively, is observed.

  1. Some physicochemical and rheological properties of starch isolated from avocado seeds.

    Science.gov (United States)

    Chel-Guerrero, Luis; Barbosa-Martín, Enrique; Martínez-Antonio, Agustino; González-Mondragón, Edith; Betancur-Ancona, David

    2016-05-01

    Seeds from avocado (Persea americana Miller) fruit are a waste byproduct of fruit processing. Starch from avocado seed is a potential alternative starch source. Two different extraction solvents were used to isolate starch from avocado seeds, functional and rheological characteristics measured for these starches, and comparisons made to maize starch. Avocado seed powder was suspended in a solution containing 2 mM Tris, 7.5 mM NaCl and 80 mM NaHSO3 (solvent A) or sodium bisulphite solution (1500 ppm SO2, solvent B). Solvent type had no influence (p>0.05) on starch properties. Amylose content was 15-16%. Gelatinization temperature range was 56-74 °C, peak temperature was 65.7 °C, and transition enthalpy was 11.4-11.6J/g. At 90 °C, solubility was 19-20%, swelling power 28-30 g water/g starch, and water absorption capacity was 22-24 g water/g starch. Pasting properties were initial temperature 72 °C; maximum viscosity 380-390 BU; breakdown -2 BU; consistency 200 BU; and setback 198 BU. Avocado seed starch dispersions (5% w/v) were characterized as viscoelastic systems, with G'>G″. Avocado seed starch has potential applications as a thickening and gelling agent in food systems, as a vehicle in pharmaceutical systems and an ingredient in biodegradable polymers for food packaging. Copyright © 2016. Published by Elsevier B.V.

  2. Frugivory and the effects of ingestion by bats on the seed germination of three pioneering plants

    Science.gov (United States)

    de Carvalho-Ricardo, Maria C.; Uieda, Wilson; Fonseca, Renata Cristina B.; Rossi, Marcelo N.

    2014-02-01

    The dispersion and seedling establishment of pioneering plants can be favoured by the presence of frugivorous bats because the bats usually improve seed germination after ingestion. Although seed germinability is known to vary greatly after ingestion by different bats, the relative contribution of each bat species to seed germination within plant communities is poorly understood. In this study, we first determined the fauna of frugivorous bats in a semideciduous seasonal forest remnant in southern Brazil and subsequently identified the plant species of the seeds passed through their guts. Second, the germination performance (i.e., germination percentage and speed) of the seeds of three pioneering plants (Piper aduncum, Piper hispidinervum and Solanum granuloso-leprosum) ingested by the most abundant bats was compared with that of the non-ingested seeds (seeds collected from fruits). Additionally, the effects on seed germination of different bat species were compared. During one year, five species of frugivorous bats were caught, and the seeds of eleven identifiable plant species (not counting those of undetermined species) were found in their faeces. We found that the germination performance of the seeds of Piper species was significantly enhanced after ingestion by bats, whereas S. granuloso-leprosum seeds had neutral or reduced germinability when seeds in faeces were compared with pulp-removed seeds. Our results revealed that the bat species that were captured exerted different effects upon seed germination; such a disparity is expected to result in different rates of early establishment of these pioneer plants in tropical forests, most likely affecting forest composition and structure, particularly during the initial stages of succession.

  3. Termites and large herbivores influence seed removal rates in an African savanna.

    Science.gov (United States)

    Acanakwo, Erik Francis; Sheil, Douglas; Moe, Stein R

    2017-12-01

    Seed removal can influence plant community dynamics, composition, and resulting vegetation characteristics. In the African savanna, termites and large herbivores influence vegetation in various ways, likely including indirect effects on seed predators and secondary dispersers. However, the intensity and variation of seed removal rates in African savannas has seldom been studied. We experimentally investigated whether termites and large herbivores were important factors in the mechanisms contributing to observed patterns in tree species composition on and off mounds, in Lake Mburo National Park, Uganda. Within fenced (excluding large herbivores) and unfenced termite mound and adjacent savanna plots, we placed seeds of nine native tree species within small open "cages," accessed by all animals, roofed cages that only allowed access to small vertebrates and invertebrates, and closed cages that permitted access by smaller invertebrates only (5 mm wire mesh). We found that mean seed removal rate was high (up to 87.3% per 3 d). Mound habitats experienced significantly higher removal rates than off-mound habitats. The mean removal rate of native seeds from closed cages was 11.1% per 3 d compared with 19.4% and 23.3% removed per 3 d in the roofed and open cages, respectively. Smaller seeds experienced higher removal rates than larger seeds. Large herbivore exclusion on mounds reduced native seed removal rates by a mean of 8.8% in the open cages, but increased removal rates by 1.7% in the open cages when off-mound habitats were fenced. While removal rates from open cages were higher on active mounds (30.9%) than on inactive mounds (26.7%), the removal rates from closed cages were lower on active vs. inactive mounds (6.1% vs. 11.6%, respectively). Thus, we conclude that large herbivores and Macrotermes mounds influence seed removal rates, though these effects appear indirect. © 2017 by the Ecological Society of America.

  4. Estimation of skill of Russian mutual fund managers

    OpenAIRE

    Parshakov, Petr

    2015-01-01

    Our work is focused on Russian mutual funds managers’ skills versus luck estimating. Using bootstrap procedure we build Jensen’s alpha density for each fund. We find that only 5% of Russian equity mutual funds do have skills (in contrast to luck) to outperform the benchmark.

  5. Mutual intelligibility between closely related language in Europe.

    NARCIS (Netherlands)

    Gooskens, Charlotte; van Heuven, Vincent; Golubovic, Jelena; Schüppert, Anja; Swarte, Femke; Voigt, Stefanie

    2018-01-01

    By means of a large-scale web-based investigation, we established the degree of mutual intelligibility of 16 closely related spoken languages within the Germanic, Slavic and Romance language families in Europe. We first present the results of a selection of 1833 listeners representing the mutual

  6. Measuring the performance of mutual funds: A case study

    Directory of Open Access Journals (Sweden)

    Jakšić Milena

    2015-01-01

    Full Text Available In this paper we evaluate the performance of eight open-end mutual funds in the Republic of Serbia for the period 2009-2012, with the aim of testing the justification of active portfolio management of mutual funds, and determining the selection capability of Serbian portfolio managers. Risk-weighted returns of mutual funds are compared with the risk-weighted return of the leading Belgrade Stock Exchange index, Belex15, whereas the following are used as performance measures: Sharpe ratio (Si, Treynor ratio (Ti, and Jensen's or Alpha index (αi. The results suggest that the portfolio of Serbian mutual funds has inferior performance compared to the market portfolio, which indicates the lack of selection capabilities of domestic portfolio managers.

  7. Modeling the Substrate Skin Effects in Mutual RL Characteristics.,

    Directory of Open Access Journals (Sweden)

    D. de Roest

    2003-12-01

    Full Text Available The goal of this work was to model the influence of the substrateskin effects on the distributed mutual impedance per unit lengthparameters of multiple coupled on-chip interconnects. The proposedanalytic model is based on the frequency-dependent distribution of thecurrent in the silicon substrate and the closed form integrationapproach. It is shown that the calculated frequency-dependentdistributed mutual inductance and the associated mutual resistance arein good agreement with the results obtained from CAD-oriented circuitmodeling technique.

  8. Ranking mutual funds using Sortino method

    Directory of Open Access Journals (Sweden)

    Khosro Faghani Makrani

    2014-04-01

    Full Text Available One of the primary concerns on most business activities is to determine an efficient method for ranking mutual funds. This paper performs an empirical investigation to rank 42 mutual funds listed on Tehran Stock Exchange using Sortino method over the period 2011-2012. The results of survey have been compared with market return and the results have confirmed that there were some positive and meaningful relationships between Sortino return and market return. In addition, there were some positive and meaningful relationship between two Sortino methods.

  9. Seed population dynamics on abandoned slopes in the hill and gully Loess Plateau region of China

    Science.gov (United States)

    Yu, Weijie; Jiao, Juying

    2017-04-01

    Recovery of natural vegetation is an effective but slow approach to control the soil erosion in the Chinese hill and gully Loess Plateau region. As seed stage is particularly vulnerable to environmental conditions, characteristics of seed population should be needed to study for determining whether the recovery of natural vegetation is limited during this stage on the abandoned slopes in this region. The study was performed on three abandoned slopes in a watershed with an area of 8.27 km2in the Shaanxi province of China. The differences in soil seed banks were investigated in two different points in time, late March2011 and early April 2013. Main factors of seed population dynamics, such as seed yield of dominant species, seed inputs by seed rain as well as seed outputs through seed loss by overland flow and seedling emergence, were monitored from late March 2011 to early April 2013. In this study, seed rain densities of the main later successional species, i.e., Lespedeza davurica, Stipa bungeana and Artemisia gmelinii accounted for 51.5-71.6% of their own seed yields. The soil seed bank density in early April 2013 was larger than that in late March 2011. The density of seed inputs by seed rain was 10186 seeds•m-2, and the total seed bank, including seed rain and seeds present in the soil seed bank in late March 2011, reached a density of 15018 seeds•m-2 during the study period. Seed densities of loss due to overland flow and seedling emergence were 79 seeds•m-2 from 20 species and 938 seedlings•m-2 that belonged to 38 species during a study period, and the seed output through them accounted for 0.5% and 6.3% of the total seed bank, respectively. The study concluded that overland flow could not result in large numbers of seeds loss and seeds were accumulating in the soil seed bank due to seed rain, and vegetation succession might be limited by curbed spatial seed dispersal and seedling establishment.

  10. Spatial distribution of seeds and seedlings of two tropical tree species: Is there correspondence between patterns?

    International Nuclear Information System (INIS)

    Parrado Rosselli, Angela

    2007-01-01

    The spatial patterns of seed and seedling distribution relative to parent trees (seed and seedling shadow, respectively) were studied for Dacryodes chimantensis (Burseraceae) and Brosimum utile (Moraceae), two common tree species of terra firme forests of Colombian Amazonia. The general objective was to assess whether the patterns imposed by seed dispersal change or persist in subsequent life stages occurring during the transition from seeds/saplings to adult stages. Seed and seedling shadows on the ground were characterized for each tree species along four 50-m radial transects from the base of the parent tree. Causes of seed and seedling predation as a function of distance to the parent tree were determined, as well as the spatial consistency between life stages. Results showed that seed density of both Dacryodes and Brosimum declined leptokurtically with distance, and it was skewed towards the parent tree. However, seed density was more skewed and leptokurtic in Dacryodes than in Brosimum. The overall trend was maintained in the seedling stage of both species and was positively correlated with the distribution patterns of seeds. Seed and seedling predation were positively correlated with density and negatively correlated with the distance from the parent tree. Factors that could be generating the high consistency between the spatial patterns of seed and seedling distribution are discussed, as well as its implications in the population structure of both species and the debate on the factors that influence the spatial distribution of plant species in tropical rain forests.

  11. Anomalous behaviour of mutual information in finite flocks

    Science.gov (United States)

    Barnett, L.; Brown, J.; Bossomaier, T.

    2017-11-01

    The existing consensus is that flocks are poised at criticality, entailing long correlation lengths and a maximal value of Shannon mutual information in the large-system limit. We show, by contrast, that for finite flocks which do not truly break ergodicity in the long-observation-time limit, mutual information may not only fail to peak at criticality —as observed for other critical systems— but also diverge as noise tends to zero. This result carries implications for other finite-size, out-of-equilibrium systems, where observation times may vary widely compared to time scales of internal system dynamics; thus it may not be assumed that mutual information locates the phase transition.

  12. Generalized mutual information and Tsirelson's bound

    Energy Technology Data Exchange (ETDEWEB)

    Wakakuwa, Eyuri [Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo 113-0033 (Japan); Murao, Mio [Institute for Nano Quantum Information Electronics, The University of Tokyo, Tokyo 113-0033, Japan and Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo 113-0033 (Japan)

    2014-12-04

    We introduce a generalization of the quantum mutual information between a classical system and a quantum system into the mutual information between a classical system and a system described by general probabilistic theories. We apply this generalized mutual information (GMI) to a derivation of Tsirelson's bound from information causality, and prove that Tsirelson's bound can be derived from the chain rule of the GMI. By using the GMI, we formulate the 'no-supersignalling condition' (NSS), that the assistance of correlations does not enhance the capability of classical communication. We prove that NSS is never violated in any no-signalling theory.

  13. Mutual intelligibility between closely related languages in Europe

    NARCIS (Netherlands)

    Gooskens, C.; Heuven, van V.J.J.P.; Golubović, J.; Schüppert, A.; Swarte, F.; Voigt, S.

    2017-01-01

    By means of a large-scale web-based investigation, we established the degree of mutual intelligibility of 16 closely related spoken languages within the Germanic, Slavic and Romance language families in Europe. We first present the results of a selection of 1833 listeners representing the mutual

  14. Financial Crisis and Corporate Social Responsible Mutual Fund Flows

    OpenAIRE

    Sitikantha Parida; Zhihong Wang

    2018-01-01

    In this paper, we investigate investment flows into mutual funds that hold more high corporate social responsible stocks (top CSR funds) vs. mutual funds that hold more low corporate social responsible stocks (bottom CSR funds). Using a large sample of equity mutual funds spanning 2003–2012, we find that top CSR funds on average receive about 5% less investment per annum compared to the other funds; whereas bottom CSR funds receive about 5.6% more investments. These relative negative and posi...

  15. Performance Evaluation of Investment (Mutual Funds

    Directory of Open Access Journals (Sweden)

    Povilas Vyšniauskas

    2014-12-01

    Full Text Available The efficiency of an investment fund is one of the main components in evaluating the performance of the fund. This study seeks for introducing and comparing risk and performance evaluation ratios. The paper is aimed at testing the worked out ratios and at distinguishing between the best ones for the purpose of evaluating the performance of Lithuanian mutual funds. Scientific studies show that a standard deviation, alpha, beta, Sharpe and Treynor ratios are mostly employed for identifying the performance of mutual funds that are also compared with their benchmark index to establish if these funds are outperformed and if is it worth paying management fees to investment banks for managing mutual funds. Historical data were selected for the period from 2012-01-02 to 2013-10-15 analysing the prices of monthly funds. The paper points out the areas of a practical application of the proposed model for investment fund valuation, which may not only provide valuable outcomes for practitioners but also may inspire further research on this article.

  16. Public-channel cryptography based on mutual chaos pass filters.

    Science.gov (United States)

    Klein, Einat; Gross, Noam; Kopelowitz, Evi; Rosenbluh, Michael; Khaykovich, Lev; Kinzel, Wolfgang; Kanter, Ido

    2006-10-01

    We study the mutual coupling of chaotic lasers and observe both experimentally and in numeric simulations that there exists a regime of parameters for which two mutually coupled chaotic lasers establish isochronal synchronization, while a third laser coupled unidirectionally to one of the pair does not synchronize. We then propose a cryptographic scheme, based on the advantage of mutual coupling over unidirectional coupling, where all the parameters of the system are public knowledge. We numerically demonstrate that in such a scheme the two communicating lasers can add a message signal (compressed binary message) to the transmitted coupling signal and recover the message in both directions with high fidelity by using a mutual chaos pass filter procedure. An attacker, however, fails to recover an errorless message even if he amplifies the coupling signal.

  17. How disturbance, competition and dispersal interact to prevent tree range boundaries from keeping pace with climate change

    Science.gov (United States)

    Liang, Y.; Duveneck, M.; Gustafson, E. J.; Serra-Diaz, J. M.; Thompson, J. R.

    2017-12-01

    Climate change is expected to cause geographic shifts in tree species' ranges, but such shifts may not keep pace with climate changes because seed dispersal distances are often limited and competition-induced changes in community composition can be relatively slow. Disturbances may speed changes in community composition, but the interactions among climate change, disturbance and competitive interactions to produce range shifts are poorly understood. We used a physiologically-based mechanistic landscape model to study these interactions in the northeastern United States. We designed a series of disturbance scenarios to represent varied disturbance regimes in terms of both disturbance extent and intensity. We simulated forest succession by incorporating climate change under a high emissions future, disturbances, seed dispersal, and competition using the landscape model parameterized with forest inventory data. Tree species range boundary shifts in the next century were quantified as the change in the location of the 5th (the trailing edge) and 95th (the leading edge) percentiles of the spatial distribution of simulated species. Simulated tree species range boundary shifts in New England over the next century were far below (usually Disturbances may expedite species` recruitment into new sites, but they had little effect on the velocity of simulated range boundary shifts. Range shifts at the trailing edge tended to be associated with photosynthetic capacity, competitive ability for light and seed dispersal ability, whereas shifts at the leading edge were associated only with photosynthetic capacity and competition for light. This study underscores the importance of understanding the role of interspecific competition and disturbance when studying tree range shifts.

  18. Mathematic Model of Technical Process of Heavy Mixtures Classifying on the Basis of Dispersion of Particles Flight Path

    OpenAIRE

    Normahmad Ravshanov; Bozorboy Palvanov; Gulnora Shermatova

    2014-01-01

    The article presents mathematic model and results of computer calculations of heavy mixtures classifying and farm crops full seeds selection. They enable to determine major process parameters and variation range, providing maximum dispersion of particles flight path, depending on feedstock modules.

  19. Holographic mutual information of two disjoint spheres

    Science.gov (United States)

    Chen, Bin; Fan, Zhong-Ying; Li, Wen-Ming; Zhang, Cheng-Yong

    2018-04-01

    We study quantum corrections to holographic mutual information for two disjoint spheres at a large separation by using the operator product expansion of the twist field. In the large separation limit, the holographic mutual information is vanishing at the semiclassical order, but receive quantum corrections from the fluctuations. We show that the leading contributions from the quantum fluctuations take universal forms as suggested from the boundary CFT. We find the universal behavior for the scalar, the vector, the tensor and the fermionic fields by treating these fields as free fields propagating in the fixed background and by using the 1 /n prescription. In particular, for the fields with gauge symmetries, including the massless vector boson and massless graviton, we find that the gauge parts in the propagators play an indispensable role in reading the leading order corrections to the bulk mutual information.

  20. Mutual Fund Competition and Stock Market Liquidity

    OpenAIRE

    Massa, Massimo

    2004-01-01

    We study how competition in the mutual fund industry affects stock market liquidity. We argue that mutual fund families operate as multi-product firms, jointly choosing fees, performance and number of funds and sharing common research facilities. The family-based organization generates economies of scale in information that induce a trade off between performance and number of funds. The presence of more and relatively less-informed funds impacts the market, increasing stock liquidity. This in...