Interdrainage morphological and genetic differentiation in the Escambia Map Turtle, Graptemys ernsti

Graptemys ernsti, the Escambia Map Turtle, inhabits the Escambia/Conecuh River, the adjacent Yellow River, and the Pea River further to the east, all of which have been distinct drainage systems since the Pleistocene. We used continuous and meristic morphological and genetic data to compare populations of G. ernsti and found evidence of differences among the three drainages. Frequency of occurrence of a nasal trident differed among the three drainages. Yellow River specimens possessed unique mitochondrial haplotypes while the Conecuh and the Pea shared haplotypes. Five microsatellite loci identified the drainages as being distinct, with the strongest differentiation between the Yellow River and the other two drainages. While these differences do not appear great enough to warrant taxonomic recognition, they do suggest that each population has a distinct evolutionary and demographic history and that they should therefore be managed separately.