Conspicuous genetic structure belies recent dispersal in an endangered beach mouse (Peromyscus polionotus trissyllepsis)

Habitat fragmentation can exacerbate the impacts on population persistence in species with rapid life histories and specialized habitat requirements. We investigated genetic structuring across the range of the federally endangered (USA) Perdido Key beach mouse (PKBM), Peromyscus polionotus trissyllepsis, using 16 microsatellite loci. Between 2010 and 2012 we sampled the three core habitat areas that are separated by 3–5 km of developed area. One location GSP was re-established in 2010 with a release of 48 captive bred mice. The other two parks had a reticulate recent history, including extirpations, translocations and, a recent (2009) natural re-colonization. Our objectives were to document the level of genetic drift associated with the post-release phase at GSP over a 2-year period, and to test the hypothesis that PKBM dispersal connectivity is restricted between the three parks. The three populations were significantly genetically differentiated in 2010 and 2012 (pairwise F ST ranged from 0.135 to 0.276). However, Bayesian clustering, assignment tests and hybridization analyses revealed inter-park dispersal and reproduction in 2012 that was absent in 2010. The detection of dispersal was an important step in understanding the regulation of connectivity in this fragmented system. We propose that a combination of recent apparent population increases across the island combined with the concurrent re-establishment of beachfront vegetated sand berms encouraged inter-park dispersal detected in 2012. These results provide important information for the future conservation of beach mice inhabiting northern Gulf of Mexico and Atlantic barrier islands in light of continued development pressure.