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John R. Holsinger and David C. Culver 
our assumption that geological structure directly affects cave species 
diversity and ecological complexity appears to be supported by the dif- 
ferences noted. Clearly, those basins with limited, discontinuous expo- 
sures of cavernous limestone and restricted karst terranes, such as the 
Shenandoah, James, and Holston, have significantly fewer cave-limited 
species per unit of area than those basins with extensive, continuous 
exposures of cavernous limestone and well-developed karst terranes, 
such as the Clinch and Powell. Those basins intermediate in these geo- 
logical parameters, the Roanoke and New, fall somewhere between the 
two extremes of species diversity. Direct field observations tend to rein- 
force our assumption, namely that, by and large, we found more species 
and larger populations in the caves of the Clinch and Powell basins than 
anywhere else in the study area. 
The numbers of genera and families represented in the cave fauna 
of a basin should provide a further indication of taxonomic diversity 
and ecological complexity. In order to check this, we compiled the 
numbers of genera and families with cave-limited species in the seven 
drainage basins of the study area (Table 14). As the data indicate, the 
numbers of both genera and families are highest for the Clinch and 
Powell basins, again emphasizing that the greatest faunistic diversity 
occurs in areas with the most extensive, continuous exposure of 
cavernous limestone. 
Barr (1967b, 1968) compared the cave systems of the Appalachian 
Valley and Ridge province with those of the Mississippian limestone 
plateaus in the Interior Low Plateaus region (i.e., Mitchell Plain in 
southern Indiana, Pennyroyal Plateau in Kentucky, and the Cumber- 
land Plateau margin in Kentucky, central Tennessee, and northern Ala- 
bama) and concluded that they were ecologically very different. Ecolog- 
ical differences were attributed to differences in geological structure. 
The Paleozoic limestones (Cambrian to Mississippian) of the Appala- 
chian Valley and Ridge are faulted and folded and exposed in long, linear 
anticlinal valleys that are separated by synclinal ridges of clastic rocks. 
In comparison, the Mississippian limestones of the Interior Low Pla- 
teaus are relatively undisturbed and exposed over broad areas. Because 
of this, dispersal of troglobites in the Appalachian Valley and Ridge 
would be restricted, whereas dispersal would be enhanced in the Missis- 
sippian plateaus. This comparison was based primarily on troglobitic 
trechine beetles (especially Pseudanophthalmus ), which are represented 
by many species in both regions. But as Barr (1967b, 1968) has pointed 
out, the implications apparently apply to many other groups of caverni- 
coles as well. On a broad scale, the troglobitic fauna of the Mississip- 
pian plateau is more diverse than that of the Appalachian Valley. 
Although our comparison of drainage basins in the study area of 
Virginia and northeastern Tennessee focused on relatively small cave 
