Range-wide and regional patterns of population structure and genetic diversity in the gopher tortoise

The gopher tortoise (Gopherus polyphemus) has experienced dramatic population declines throughout its distribution in the southeastern United States and is federally listed as threatened in the area west of the Tombigbee-Mobile Rivers. While there is molecular support for recognizing the listed portion of the range as genetically distinct, other research has suggested that additional population structure exists at both range-wide and regional scales. In this study, we sought to comprehensively define structure at both spatial scales by doubling the data available in terms of the number of sampling sites, individuals and microsatellite loci compared to previously published work. Patterns of genetic diversity, gene flow and demographic history were also compared across the range. We collected 933 individuals from 47 sampling sites across the range and genotyped them for 20 microsatellite loci. Our range-wide analyses supported the recognition of five genetic groups (or regions) delineated...