Abstract
Gene flow dictates a broad range of ecological and evolutionary processes. Understanding the factors mediating magnitude and direction of gene flow is crucial for interpreting patterns of genetic diversity and for answering many kinds of biological questions. Recent advances at the interface of population genetics and GIS technology have expanded our perspective of the geographic and physical features influencing gene flow and, in turn, shaping genetic structure of populations. I investigated the effect of surface-level trade winds on genetic structure and gene flow in two species of phyllostomid bats in the Bahamas and Greater Antilles: Erophylla sezekorni (the buffy flower bat) and Macrotus waterhousii (Waterhouse's leaf-nosed bat). Bayesian Clustering Analysis revealed that all islands sampled represent independent genetic populations for M. waterhousii but not for E. sezekorni. Samples from 13 islands (spanning E. sezekorni's range) clustered into five genetic populations and revealed the existence of two main clades (eastern: Hispaniola and Puerto Rico; western: Cuba, Jamaica, and Bahamas). To test the hypothesis that surface-level trade winds mediate gene flow in this system, I generated measures of effective distance between islands using anisotropic cost modeling based on wind data from the National Climactic Data Center. Both species exhibited significant isolation by distance with geographical distance and some of the measures of effective distance, but effective distance did not provide increased explanatory power in predicting distribution of genetic diversity. The IBDGEO slope was steeper for E. sezekorni than M. waterhousii, suggesting greater dispersal ability in the former species. According to Maximum Likelihood analysis, a majority (80%) of gene flow between genetic populations was asymmetric in both species. The degree of asymmetric gene flow between populations was not explained by the degree of asymmetry in effective distance or island area, indicating an unknown mechanism driving asymmetric gene flow. More information about the ecology of these taxa is required to understand the incidence of asymmetric gene flow in this system. The results of this study suggest that gene flow among islands is highly restricted for M. waterhousii and that this species deserves greater taxonomic attention and conservation concern.