Bachman's Sparrow (Peucaea aestivalis) population structure across the southeastern USA

Understanding gene flow and population structure in wildlife populations helps managers to protect distinct genetic lineages and genetic variation in small, isolated populations at high risk of extinction. I assessed genetic diversity in Bachman’s Sparrows (Peucaea aestivalis) to evaluate the role of natural barriers in shaping evolutionarily significant units as well as the effect of anthropogenically-caused habitat loss and fragmentation on population differentiation and diversity. Genetic diversity was assessed across the geographic range of Bachman’s Sparrow by genotyping 226 individuals at 18 microsatellite loci and sequencing 48 individuals at nuclear and mitochondrial DNA genes. Multiple analyses consistently demonstrated high levels of gene flow, which appear to have maintained high levels of genetic variation and panmixia in populations throughout the species’ range. Based on these genetic data, separate management units/subspecies designations or artificial gene flow among populations in habitat fragments do not seem necessary. High vagility in Bachman’s Sparrow may be an adaptation to colonize ephemeral, fire-mediated longleaf pine habitat, but in recent times, it also appears to have reduced inbreeding and loss of genetic diversity in habitat fragments.