A FLY ON THE CAVE WALL: PARASITE GENETICS REVEAL FINE-SCALE DISPERSAL PATTERNS OF BATS

Dispersal influences the evolution and adaptation of organisms, but can be difficult to detect. Host-specific parasites provide information about the dispersal of their hosts and may be valuable for examining host dispersal that does not result in gene flow or low signals of gene flow. We examine the population connectivity of the buffy flower bat, Erophylla sezekorni (Chiroptera: Phyllostomidae), and its associated obligate ectoparasite, Trichobius frequens (Diptera: Streblidae), across a narrow oceanic channel in The Bahamas that has previously been implicated as a barrier to dispersal in bats. Due to the horizontal transmission of T. frequens, we are able to test the hypothesis that bats are dispersing across this channel, but this dispersal does not result in gene flow, occurs rarely, or started occurring recently. We develop novel microsatellite markers for the family Streblidae in combination with previously developed markers for bats to genotype individuals from 4 islands in The Bahamas. We provide evidence for a single population of the host, E. sezekorni, but 2 populations of its bat flies, potentially indicating a recent reduction of gene flow in E. sezekorni, rare dispersal, or that bat flies are infrequently transported with their hosts. Despite high population differentiation in bat flies indicated by microsatellites, mitochondrial DNA shows no polymorphism, suggesting that bacterial reproductive parasites may be contributing to mitochondrial DNA sweeps. Parasites, including bat flies, provide independent information about their hosts and can be used to test hypotheses of host dispersal that may be difficult to assess using host genetics alone.