Invertebrate Cave Fauna 
123 
Table 14. Frequency distribution by drainage basin of genera and families with 
cave-limited species. 
Drainage Basin 
Number of Genera 
Number of Families 
Shenandoah 
17 
12 
James 
17 
13 
Roanoke 
10 
8 
New 
15 
13 
Holston 
11 
9 
Clinch 
23 
17 
Powell 
21 
17 
regions within a single physiographic province and considered trechine 
beetles as well as all other groups of cave-limited species, our findings 
are essentially the same as those of Barr. The results of both of these 
studies corroborate the hypothesis that in a geographic region where 
climatic conditions are historically similar, areas with extensive, contin- 
uous exposures of cavernous limestone will harbor more diverse troglo- 
bite faunas than areas with limited, discontinuous exposures of limestone. 
The data from two other studies, both on Appalachian cave faunas, 
also tend to corroborate this hypothesis. In a study of the invertebrate 
cave fauna of West Virginia (Holsinger et al. 1976), we documented a 
significantly richer troglobitic fauna in the Greenbrier Valley than in 
any other limestone region of that state. Like the Clinch and Powell 
valleys in Virginia, the Greenbrier Valley contains extensive, continuous 
exposures of cavernous limestone and a well-developed karst terrane; 
cave density is very high. In other major cave regions of West Virginia 
(e.g., the Monongahela and Potomac basins), where limestone expo- 
sures and karst terranes are more restricted and cave density is lower, 
the troglobitic faunas are correspondingly less diverse. In the other 
study, the troglobitic fauna of Pennsylvania was compared on a broad, 
regional scale with that of the Virginias (Holsinger 1976). In Pennsylva- 
nia, limestone areas are mostly very narrowly delimited, and caves are 
typically very small. The troglobitic fauna is exceedingly sparse (only 15 
species) and contains largely aquatic species, some of which are stygobi- 
onts. In contrast, the troglobitic fauna of the Virginias, where cavernous 
limestone areas are generally much more extensive, is significantly 
richer. Although, admittedly, the proximity of the cave region of Penn- 
sylvania to Pleistocene glaciation probably has had something to do 
with its impoverished troglobitic fauna (Holsinger 1976), the effect of 
geological structure has probably been of equal or greater significance 
(Holsinger 1976). 
