Microspatial sampling reveals cryptic influences on gene flow in a threatened mammal

Abstract

We studied the population structure and historical demography of the last remaining core population of the threatened southeastern beach mouse (SEBM; Peromyscus polionotus niveiventris) located on a federally protected barrier island complex at the Kennedy Space Center (KSC), Merritt Island National Wildlife Refuge (MINWR) and Cape Canaveral Air Force Station (CCAFS) in Florida, USA. Beach mice (N = 171) were collected from 33 trapping locations along 30 km of coastline on KSC/MINWR/CCAFS and were genotyped using 10 microsatellite loci. We found four genetic clusters of mice that likely form a metapopulation. Gene flow among clusters, assessed using assignment tests, was limited suggesting that human development can serve to inhibit dispersal of beach mice. However, when the presence of roads were examined as possible barriers to movement, gene flow appeared to be facilitated suggesting that removal of thick vegetation along roadsides increases movement. We used approximate Bayesian computation (ABC) to estimate divergence time among clusters and effective population sizes for each cluster and for the pre-divergence population. Results of ABC analyses suggest that barriers to movement likely formed following the construction of the John F. Kennedy Space Center beginning in the 1960s but that this has not heavily impacted the effective size of populations. Pre-divergence and contemporary effective sizes are similar, thus, population sizes likely remained relatively large over the last 50–100 years. The population of SEBM on KSC/MINWR/CCAFS appears to be a genetically diverse core population and individuals from this population will most likely be good candidates for any future reintroduction and translocation programs.