Morphological and molecular evidence indicates that the Gulf Coast box turtle (Terrapene carolina major) is not a distinct evolutionary lineage in the Florida Panhandle

Four extant subspecies of Terrapene carolina in eastern North America, Terrapene carolina bauri, Terrapene carolina carolina, Terrapene carolina triunguis, and Terrapene carolina major, are recognized based on morphological studies. A fifth subspecies, Terrapene carolina putnami, has been described from Pleistocene deposits but is very similar morphologically to T. c. major. Questions concerning the relationship of the Gulf Coast box turtle (T. c. major) to other box turtles have been pervasive ever since it was described. We used a combined morphological and genetic analysis to address the status of T. c. major and other T. carolina lineages. Terrapene c. bauri, T. c. carolina, and T. c. triunguis are distinct based on a discriminate function analysis of 25 morphological characters, including characters traditionally used to assign subspecies. The results of the present study confirm that box turtles phenotypically diagnosed as T. c. bauri, T. c. carolina, and T. c. triunguis all occur within the hypothesized range of T. c. major, and that the latter does not possess a diagnosable morphology. The three morphological lineages also possess divergent mitochondrial haplotypes that are present within the hypothesized range of T. c. major. In addition, a fourth distinct mtDNA lineage co-occurs within the putative range of T. c. major. This unique lineage may include mitochondrial DNA variation from the Pleistocene T. c. putnami. Analysis of nine nuclear DNA microsatellites revealed no population structure in box turtles currently assigned to T. c. major from the Florida Panhandle, suggesting a complete admixture of lineages in this region. The results of the present study indicate that box turtles traditionally assigned to T. c. major based on phenotype are the result of introgression between eastern extant (predominantly T. c. carolina) and an extinct subspecies, T. c. putnami.