title: Spatio-temporal Genetic Structure of a Tropical Bee Species Suggests High Dispersal Over a Fragmented Landscape.
abstract: Habitat destruction threatens biodiversity by reducing the amount of available resources and connectivity among geographic areas. For organisms living in fragmented habitats, population persistence may depend on dispersal, which maintains gene flow among fragments and can prevent inbreeding within them. It is centrally important to understand patterns of dispersal for bees living in fragmented areas given the importance of pollination systems and recently documented declines in bee populations. We used population and landscape genetic techniques to characterize patterns of dispersal over a large fragmented area in southern Costa Rica for the orchid bee speciesEuglossa championi. First, we estimated levels of genetic differentiation among forest fragments as φpt, an analog to the traditional summary statisticFst, as well as two statistics that may more adequately represent levels of differentiation,G'standDest. Second, we used a Bayesian approach to determine the number and composition of genetic groups in our sample. Third we investigated how genetic differentiation changes with distance. Fourth, we determined the extent to which deforested areas restrict dispersal. Finally, we estimated the extent to which there were temporal differences in allele frequencies within the same forest fragments. Within years we found low levels of differentiation even over 80 km, and no effect of land use type on level of genetic differentiation. However, we found significant genetic differentiation between years. Taken together our results suggest that there are high levels of gene flow over this geographic area, and that individuals show low site fidelity over time.
authors.affiliation: Center for Insect Science, University of Arizona, Tucson AZ 85721, U.S.A ; Center for Insect Science, University of Arizona, Tucson AZ 85721, U.S.A ; Organismic and Evolutionary Biology Program, University of Massachusetts, Amherst MA 01003, U.S.A.
authors.forename: Sevan S
authors.initials: SS
authors.lastname: Suni
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson AZ 85721, U.S.A.
authors.forename: Judith L
authors.initials: JL
authors.lastname: Bronstein
authors.affiliation: Department of Environmental Studies, Emory University, Atlanta GA 30322, U.S.A.
authors.forename: Berry J
authors.initials: BJ
authors.lastname: Brosi
keywords: dispersal; euglossine; fragmentation; genetic differentiation; landscape genetics; orchid bee