Population structure and cryptic evolutionary units in the alligator snapping turtle

The alligator snapping turtle (Macroclemys temminckii) is a long-lived, slo w-growing chelydrid turtle found in Gulf of Mexico drainages from Florida t o Texas (U.S.A). Populations are thought to be depleted throughout the rang e due in part to an increased harvest in the 1960s through 1980s. To identi fy population and evolutionary units, 420 base pairs were sequenced within the mitochondrial DNA control region of 158 specimens from 12 drainages. Re sults indicate substantial phylogeographic structuring and strong populatio n-level separations among river drainages. Eight of 11 haplotypes were obse rved to be river-specific, providing diagnostic markers for most drainages Three partitions are resolved in the mtDNA genealogy, corresponding to the Eastern, central, and western portion of the species' range. These separati ons coincide with recognized biogeographic provinces. The population struct ure by river system indicates that many drainages are distinct management u nits, with the Suwannee River lineage Possibly deserving special attention, based on the criterion of genetic distinctiveness. The partitioning of M. temminckii into river-specific populations illustrates the management frame work and conservation challenges that apply to a broad array of riverine sp ecies. Drainage-specific molecular markers may be used to identify the geog raphic origin of turtle products in the marketplace.