Invertebrate Cave Fauna 
119 
Table 12. Number of cave-liriiited species shared by drainage basins. Data 
based on species listed in Tables 5 through 1 1. 
Drainage 
Basin 
Shenandoah 
James 
Roanoke 
• 
New 
Holston 
Clinch 
Powell 
Shenandoah 
- 
5 
2 
3 
2 
3 
2 
James 
5 
- 
5 
8 
4 
7 
3 
Roanoke 
2 
5 
- 
6 
3 
4 
3 
New 
3 
8 
6 
- 
1 1 
10 
7 
Holston 
2 
4 
3 
11 
- 
10 
9 
Clinch 
3 
7 
4 
10 
10 
- 
15 
Powell 
2 
3 
3 
7 
9 
15 
- 
cantly more cave-limited species and ecologically more complex cave 
communities than others, and, that with few exceptions, cave species 
diversity and ecological complexity increased in those areas with large 
numbers of caves and extensive karst development. To gain a better 
understanding of this apparent relationship and to translate it into 
quantitative terms, we compiled the data shown in Table 13. As these 
data indicate, there are major differences among the seven drainage bas- 
ins with respect to area, number of cave-limited species, and number of 
recorded caves. In order to demonstrate the relationship between these 
variables concisely, we calculated both species density and cave density 
per unit of area for each basin (Table 13). We then plotted these values 
and found a strong linear relationship between species density and cave 
density in the different basins (Fig. 37). There is a progressive increase 
in density of species per unit of area from the Shenandoah basin, with 
the lowest cave density, to the Powell basin, with the highest cave den- 
sity. The slope of the regression line in Figure 37 is highly significant (b 
= 0.13, p < .001) and 92% of the variation can be explained by variation 
in cave density. 
Cave density alone probably does not determine the number of 
cave-limited species in a given area or basin. Other factors, which are 
more difficult to quantify, but probably equally important in determin- 
ing the species diversity of a faunal unit, include both the amount and 
continuity of exposed, cavernous limestone and the degree of karst 
development. Cave density, however, which can be easily calculated for 
an area where the caves are well documented, is an excellent indication 
of the extent of cavernous limestone and also often reflects the extent of 
karst development. 
