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Peter M Hollingsworth - One of the best experts on this subject based on the ideXlab platform.

Mauricio Quesada - One of the best experts on this subject based on the ideXlab platform.

  • effects of Forest Fragmentation on pollinator activity and consequences for plant reproductive success and mating patterns in bat pollinated bombacaceous trees1
    Biotropica, 2004
    Co-Authors: Mauricio Quesada, Kathryn E Stoner, Jorge A Lobo, Yvonne Herreriasdiego, Carolina Palaciosguevara, Miguel A Munguiarosas, Karla A O Salazar, Victor Rosasguerrero
    Abstract:

    ABSTRACT Forest Fragmentation and the resulting spatial isolation of tree species can modify the activity of pollinators and may have important implications for the reproductive success and mating systems of the plants they pollinate. The objectives of this study were to (1) evaluate the effect of Forest Fragmentation on pollinator activity in bat-pollinated bombacaceous trees and (2) determine the effects of Forest Fragmentation on reproductive success and mating systems of bombacaceous trees. We studied these parameters in three bombacaceous tree species in tropical seasonal Forest of Chamela, Jalisco, Mexico, and Osa and Guanacaste, Costa Rica. For Ceiba aesculifolia, more visits were observed in fragments by both Glossophaga soricina and Leptonycteris curasoae. For Ceiba grandiflora, Musonycteris harrisoni visited flowers exclusively in Forest and G. soricina visited more flowers in Forest than in fragments; no difference was shown by L. curasoae. For Ceiba pentandra in Chamela, no differences were fo...

  • effects of Forest Fragmentation and flowering phenology on the reproductive success and mating patterns of the tropical dry Forest tree pachira quinata
    Conservation Biology, 2003
    Co-Authors: Eric J Fuchs, Jorge A Lobo, Mauricio Quesada
    Abstract:

    The results of several studies suggest that Forest Fragmentation affects the mating patterns and re- productive success of tropical tree species by reducing pollinator activity, pollen deposition, and outcrossing levels. The flowering synchrony of trees has also been proposed as an additional factor in controlling fruit set and regulating levels of outcrossing, particularly in disturbed habitats. We examined the effects of Forest frag- mentation and flowering phenology on the reproductive success and genetic structure of the progeny pro- duced by the tropical tree Pachira quinata . We conducted our study in the dry Forest of Costa Rica and com- pared trees in two density and environmental conditions: (1) isolated trees separated by 500 m from other adult conspecifics and located in disturbed sites and (2) trees from continuous populations of groups of 20 or more reproductive individuals per hectare surrounded by undisturbed mature Forest. Our study was con- ducted in the Guanacaste Conservation Area, Costa Rica, and surrounding areas. To evaluate flowering phe- nology, trees were classified as having synchronous or asynchronous flowering. The phenological stage of in- dividuals was classified according to the proximity of the peak flowering date of each tree with respect to the mean peak flowering of the rest of the population. Six percent of the flowers produced a fruit in trees from continuous populations, whereas in isolated trees only 3% of the flowers did so. Fruit set was not affected by the flowering phenology of trees but was influenced mainly by factors associated with Forest Fragmentation. Seed production per fruit was not affected by Forest Fragmentation or flowering phenology. Overall, total fruit production per tree was not affected by Forest Fragmentation, because isolated trees tended to produce more flowers than trees from continuous populations. Genetic analysis revealed that the progeny of trees from con- tinuous populations experienced lower levels of relatedness, a tendency for higher levels of outcrossing, and/ or more sires than isolated trees. Our results suggest that Forest Fragmentation can have an effect on the mat- ing patterns of P. quinata , reducing the number of outcross sires represented in the progeny of isolated trees.

  • effects of dry tropical Forest Fragmentation on the reproductive success and genetic structure of the tree samanea saman
    Conservation Biology, 2002
    Co-Authors: Alfredo Cascante, Mauricio Quesada, Jorge J Lobo, Eric A Fuchs
    Abstract:

    : Tropical trees are particularly vulnerable to Forest Fragmentation because of their low densities, self-incompatibilty system, and high rates of outbreeding. Forest Fragmentation is likely to decrease gene flow, increase endogamy, and eventually produce a high differentiation among remnant populations. Our objectives were to evaluate the effect of Forest Fragmentation on the reproductive success, progeny vigor, and genetic variation of the tropical dry-Forest tree Samanea saman. We conducted our study in the dry Forest of Costa Rica and compared two tree conditions to evaluate Forest Fragmentation: (1) isolated, individual trees more than 500 m from the nearest conspecific and surrounded by agricultural fields, pastures, or small remnant Forest patches and (2) trees in continuous populations of 10 or more individuals per hectare and surrounded by undisturbed Forest. We compared the probability of natural pollination, seed production, genetic variation, and progeny vigor of trees in isolation and in continuous populations. The probability of flowers receiving more than 23 pollen tubes at the base of styles (the flowers more likely to produce a mature fruit) was significantly greater for trees in continuous populations (2.1%) than for trees in isolation (0.4%). However, flowers from the two tree conditions received similar pollen loads on their stigmas. Fruits of trees from continuous populations produced similar numbers of seeds as isolated trees did and had a similar probability of seed abortion. The probability of seed predation by bruchid beetles was significantly greater in continuous populations (30%) than in isolated trees (20%). The number of undamaged seeds (  potentially viable) was similar for both tree conditions. A genetic analysis of progeny showed that levels of genetic diversity in trees in isolation and in continuous populations were comparable. The effective self-fertilization rate and inbreeding coefficient of the progeny were slightly higher for isolated trees than for trees in continuous populations. In addition, there was more genetic similarity in the progeny of isolated trees, within and between fruits. Seeds produced by different fruits within a tree were more likely to be related in an isolated tree than in a tree from continuous populations. Seeds produced by trees from continuous populations were more likely to germinate and to produce greater leaf area and biomass as seedlings than progeny from isolated trees. We concluded that the Fragmentation of tropical dry Forests affects the genetic variation and vigor of S. saman progeny. Isolated trees showed high reproductive capacity, however, in spite of their habitat condition. Resumen: Los arboles tropicales son particularmente vulnerables a la fragmentacion de bosques debido a su baja densidad, su sistema de auto-incompatibilidad y altas tasas de exogamia. La fragmentacion del bosque posiblemente decrece el flujo de genes, incrementa la endogamia y eventualmente produce una alta diferenciacion entre las poblaciones remanentes. Nuestros objetivos fueron evaluar el efecto de la fragmentacion del bosque sobre el exito reproductivo, el vigor de la progenie y la variacion genetica del arbol de bosque tropical seco Samanea saman. Realizamos nuestro estudio en el bosque tropical seco de Costa Rica y comparamos dos condiciones de los arboles para evaluar la fragmentacion del bosque: (1) individuos aislados mas de 500 m del individuo conespecifico mas cercano y rodeados por campos agricolas, ganaderos o pequenos fragmentos de bosque y (2) arboles en poblaciones continuas de 10 o mas individuos por hectarea y rodeados de bosque no perturbado. Comparamos la probabilidad de la polinizacion natural, produccion de semillas, variacion genetica y vigor de la progenie en arboles aislados y en poblaciones continuas. La probabilidad de que las flores reciban mas de 23 tubos de polen en la base de los pistilos (  las flores con mayor probabilidad de producir un fruto maduro) fue significativamente mayor para arboles en poblaciones continuas (2.1%) que en arboles aislados (0.4%). Sin embargo, flores en arboles en las dos condiciones recibieron similares cargas de polen en sus estigmas. Los frutos de arboles de poblaciones continuas produjeron similares numeros de semillas y tuvieron similar probabilidad de abortar que los de arboles aislados. La probabilidad de depredacion de semillas por escarabajos bruquidos fue significativamente mayor en las poblaciones continuas (30%) que en arboles aislados (20%). El numero de semillas sin dano (  potencialmente viables) fue similar en arboles en las dos condiciones. El analisis genetico de la progenie mostro que los niveles de diversidad genetica de arboles aislados y en poblaciones continuas fueron comparables. La tasa de autofecundacion efectiva y el coeficiente de endogamia de la progenie fue ligeramente mayor en arboles aislados que en los de poblaciones continuas. Adicionalmente, hubo mayor similitud genetica en la progenie de arboles aislados, dentro y entre frutos. Semillas producidas por distintos frutos del mismo arbol tuvieron mas probabilidad de relacion que los de poblaciones continuas. Semillas producidas por arboles en poblaciones continuas tuvieron mayor posibilidad de germinar y producir mayor area foliar y biomasa que las plantulas de la progenie de arboles aislados. Concluimos que la fragmentacion de bosques tropicales secos afecta la variacion genetica y el vigor de la progenie de S. saman. Sin embargo, los arboles aislados tuvieron una alta capacidad reproductiva a pesar de la condicion de su habitat.

Noel Tawatao - One of the best experts on this subject based on the ideXlab platform.

  • impacts of Forest Fragmentation on the genetic diversity and population structure of pachycondyla obscurans in sabah malaysian borneo
    Asian Myrmecology, 2011
    Co-Authors: Noel Tawatao, Chey Vun Khen, Neil E Harper, Maryati Mohamed, Jeremy B Searle, Jane K Hill
    Abstract:

    The impact of Forest Fragmentation on genetic diversity of Pachycondyla obscurans, a predatory Forest-specialist ant species, was investigated in six Forest locations using Amplified Fragment Length Polymorphism (AFLP) fingerprinting. There was little difference in genetic diversity between three large Forest locations (two locations in continuous Forest, plus one 120,000 ha fragment) and three small Forest fragments (151–320 ha). Populations from two locations approximately 60 km apart in continuous Forest showed little genetic differentiation, but genetic differences between all other locations (35–164 km apart), which are separated by oil palm plantations, were much greater. There was no significant relationship between geographical distance and genetic distance (pairwise FST values) between locations. Overall, we conclude that the genetic diversity of P. obscurans has not been affected by habitat Fragmentation over the past fifty years, but locations separated by Forest were more genetically similar than those separated by agricultural areas. This implies that an inhospitable intervening matrix may prevent ant dispersal, and may result in genetic erosion of insect populations in the longer term.

  • ecological impacts of tropical Forest Fragmentation how consistent are patterns in species richness and nestedness
    Philosophical Transactions of the Royal Society B, 2011
    Co-Authors: Jane K Hill, Michael A Gray, Chey Vun Khen, Suzan Benedick, Noel Tawatao, Keith C Hamer
    Abstract:

    Large areas of tropical Forest now exist as remnants scattered across agricultural landscapes, and so understanding the impacts of Forest Fragmentation is important for biodiversity conservation. We examined species richness and nestedness among tropical Forest remnants in birds (meta-analysis of published studies) and insects (field data for fruit-feeding Lepidoptera (butterflies and moths) and ants). Species–area relationships were evident in all four taxa, and avian and insect assemblages in remnants typically were nested subsets of those in larger areas. Avian carnivores and nectarivores and predatory ants were more nested than other guilds, implying that the sequential loss of species was more predictable in these groups, and that Fragmentation alters the trophic organization of communities. For butterflies, the ordering of fragments to achieve maximum nestedness was by fragment area, suggesting that differences among fragments were driven mainly by extinction. In contrast for moths, maximum nestedness was achieved by ordering species by wing length; species with longer wings (implying better dispersal) were more likely to occur at all sites, including low diversity sites, suggesting that differences among fragments were driven more strongly by colonization. Although all four taxa exhibited high levels of nestedness, patterns of species turnover were also idiosyncratic, and thus even species-poor sites contributed to landscape-scale biodiversity, particularly for insects.

Daniel Tregidgo - One of the best experts on this subject based on the ideXlab platform.

Berry J Brosi - One of the best experts on this subject based on the ideXlab platform.

  • the effects of Forest Fragmentation on euglossine bee communities hymenoptera apidae euglossini
    Biological Conservation, 2009
    Co-Authors: Berry J Brosi
    Abstract:

    Abstract Despite scientific and media attention on pollinator declines, there is still only a rudimentary understanding of the response of bees—the most important group of pollinators worldwide—to ongoing land use changes. Euglossine bees are an ecologically important Neotropical clade of Forest-dependent pollinators. Despite the fact that euglossines are well studied relative to other groups of tropical bees, only three previous studies, all from Brazil, address the response of euglossines to Forest Fragmentation. In this study, I tripled the maximum sample size of previous efforts by sampling male euglossines in 22 Forest fragments ranging in area from 0.25 ha to 230 ha in southern Costa Rica, using chemically baited Van Someren traps. Abundance of euglossine bees was significantly positively related to Forest fragment size, negatively related to shape (edge:area ratio), and marginally related to fragment isolation. Euglossine species richness showed similar, but weaker trends: richness was significantly positively related to the quantity of Forest edge, marginally negatively related to fragment area, and not related to fragment isolation. The positive relationship between euglossine richness and abundance and Forest fragment edge is consistent with other studies that have found high euglossine density in secondary or disturbed Forest. The data suggest that individual euglossines move between Forest fragments, as has been shown in other systems. Still, Forest Fragmentation appears to affect euglossine bees more strongly than other bee groups in the study region. Their large flight range and positive relationship with Forest edges may help to buffer the negative effects of Fragmentation, allowing euglossines to utilize even the very smallest Forest fragments in the study area.

  • the effects of Forest Fragmentation on bee communities in tropical countryside
    Journal of Applied Ecology, 2007
    Co-Authors: Berry J Brosi, Gretchen C Daily, Tiffany Shih, Federico Oviedo, Guillermo Duran
    Abstract:

    Summary 1. Despite ongoing concerns and controversy over a putative ‘global pollination crisis’ there is little information on the response of bees, the most important group of pollinators, to land-use change. In particular, there are no published studies of the effects of tropical Forest Fragmentation on entire bee communities. 2. We examined bee community responses to Forest fragment size, shape, isolation and landscape context (Forest variables) by sampling foraging bees at ground level using aerial netting within, and in pastures adjacent to, 22 Forest fragments ranging in area from c. 0·25 ha to 230 ha, in southern Costa Rica. We sampled each site 13 times in total, in both wet and dry seasons. 3. Although there were no effects of Forest variables on bee diversity and abundance, we did find strong changes in bee community composition. In particular, tree-nesting meliponines (social stingless bees) were associated with larger fragments, smaller edge:area ratios and greater proportions of Forest surrounding sample points, while introduced Apis showed opposite patterns. 4. Community composition was also strikingly different between Forests and pastures, despite their spatial proximity. In Forests, even in the smallest patches, meliponines comprised a much larger proportion of the apifauna, and orchid bees (euglossines) were common. In pastures, Apis was much more abundant and no euglossine bees were found. 5. These results agree broadly with other studies that have found contrasting responses to habitat Fragmentation from different bee groups. Conserving meliponine bees, important for pollination of coffee and other crops, and euglossine bees, critical in long-distance pollen transport, will require Forest. 6. Synthesis and applications . In the first study of the effects of tropical Forest Fragmentation on entire understorey bee assemblages, we found bee community resilience to land-use change, as deForested sites and small Forest fragments can have a diverse component of bees. While bees as a whole show some degree of resilience to land-use change, there are taxon-specific responses and, in our study area, there is clear value to conserving native Forest, particularly for the ecologically and economically important meliponine and euglossine bees.