Some taxonomists have attempted to separate white-tailed deer into a host of subspecies, based largely in morphological differences. Genetic studies,[clarification needed] however, suggest fewer subspecies within the animal's range, as compared to the 30 to 40 subspecies that some scientists described in the last century. The Florida Key deer, O. v. clavium, and the Columbian white-tailed deer, O. v. leucurus, are both listed as endangered under the U. S. Endangered Species Act. In the United States, the Virginia white-tail, O. v. virginianus, is among the most widespread subspecies. The white-tailed deer species has tremendous genetic variation and is adaptable to several environments. Several local deer populations, especially in the southern states, are descended from white-tailed deer transplanted from various localities east of the Continental Divide. Some of these deer populations may have been from as far north as the Great Lakes region to as far west as Texas, yet are also quite at home in the Appalachian and Piedmont regions of the south. These deer, over time, have intermixed with the local indigenous deer (O. v. virginianus and/or O. v. macrourus) populations.