30 Robert Wayne Van Devender and Paul F. Nicoletto 



abundant basking sites to overcome locally cooler daytime tempera- 

 tures. Warmer evening and winter temperatures provide a relatively sta- 

 ble environment, and deep fissures permit escape from the occasional 

 severe surface conditions. This combination of conditions probably 

 occurs in other protected montane areas that could also support popula- 

 tions of these and/ or other species that prefer warmer conditions. 



Arrival of these species in the Wilson Creek area may be a rela- 

 tively recent event or a more ancient one. Recent arrival would proba- 

 bly be the result of immigration by populations expanding up the 

 Catawba and Johns rivers into the area. Since there is no other evidence 

 for recent range expansions of native reptiles in the eastern United 

 States, it is unlikely that this hypothesis is accurate. We consider these 

 populations to be relicts and offer the following hypothesis about their 

 origins. 



During the last glacial maximum, about 18,000 years ago (yr BP), 

 essentially all of the Coastal Plain of the Carolinas was occupied by a 

 relatively Boreal forest of spruce and jack pines, indicative of a much 

 cooler climate that excluded most southern plants and many southern 

 animals (e.g. Watt 1979, 1980; Watt and Stuiver 1980; Flint 1971; Del- 

 court 1980; Wright 1976). The reptile species now characteristic of the 

 Coastal Plain, including the four relicts at Wilson Creek, were found 

 only much farther south. The warming trend that led to the retreat of 

 the glaciers also resulted in the immigration of southern plants and 

 animals into the Carolina Coastal Plain (Delcourt 1980; Webb 1981; 

 Watts 1979, 1980; Watts and Stuiver 1980). The warming trend reached 

 its climax in the Hypsithermal Interval when conditions were warmer 

 and drier than they are today (Webb 1981; Wright 1976; Deevey and 

 Flint 1957; Watts 1980; Watts and Stuiver 1980). In a few areas the 

 Hypsithermal lasted until about 5000 yr BP (Delcourt 1980; Watts 1979) 

 when the cooler, wetter climate of today was established. 



By the end of the Hypsithermal, animals and plants should have 

 spread throughout climatically suitable areas. Reptiles are somewhat 

 limited by climate, so their distributions should have been more exten- 

 sive at the end of the Hypsithermal than they are today. The '^ooling 

 trend of the last 5000 to 7000 years should have resulted in local extinc- 

 tion of reptile populations as conditions became too severe, and in a 

 general contraction of species' ranges to those seen today. Special local 

 conditions, such as those of lower Wilson Creek or the gorges of the 

 Southern Blue Ridge escarpment, could forestall local extinctions of 

 reptiles by limiting the impact of the cooling trend (Billings and Ander- 

 son 1966; Anderson and Zander 1973; Bruce 1965). The result of this 

 protection would be isolated, relict populations in refugia well separated 

 from the main range of the species, as seen in the reptiles of lower Wil- 

 son Creek. 



