MOLECULAR SYSTEMATICS OF MAP TURTLES (GRAPTEMYS) - A COMPARISON OF MITOCHONDRIAL RESTRICTION SITE VERSUS SEQUENCE DATA

Analyses of mitochondrial DNA (mtDNA) restriction sites and sequences were used to estimate phylogenetic relationships in the emydid turtle genus Graptemys. We compared resolution and concordance among four mtD NA data sets: (1) restriction sites, (2) cytochrome b sequences (380 b ase positions [bp]), (3) control region sequences (344 bp), and (4) co mbined (cytochrome b and control region) sequences. Five of the 12 cur rently recognized species could not be distinguished on the basis of r estriction sites. Cytochrome b sequences provided even less phylogenet ic information, whereas control region sequences identified all taxa. Bootstrap consensus trees for the restriction site and control region sequence data resolved three monophyletic clades: a pulchra group, a p seudogeographica group, and the basal G. geographica. Of the four data sets, the control region offered the greatest resolution with respect to species identification and phylogenetic information. However, a ch aracter congruence approach, combining both sequence and restriction s ite characters, significantly bolstered bootstrap support for the majo r clades and enhanced phylogenetic resolution within them. Sequence di vergence estimates (restriction sites: 0.0-3.2%; cytochrome b: 0.0-1.5 %) for Graptemys are among the lowest values reported for a generic-le vel comparison involving vertebrates. These Endings are discussed in l ight of recent drainage isolation events along the Gulf of Mexico and a proposed slow rate of mtDNA evolution in turtles.