Invertebrate Cave Fauna 
127 
Table 15. Summary of data on area used in regression analysis. 
Drainage 
Basin 
Area(km 2 ) 
% Limestone 
Limestone 
Area(km 2 ) 
Number 
of Caves* 
Shenandoah 
8328 
46 
3847 
396 
James 
7745 
38 
2943 
431 
Roanoke 
1073 
36 
386 
91 
New 
4087 
33 
1349 
419 
Holston 
3690 
62 
2288 
308 
Clinch 
4048 
55 
2210 
537 
Powell 
2278 
43 
981 
394 
♦Includes all caves recorded from the study area through 1980. 
Table 16. 
Comparison of regression equations using data in Tables 5 through 
11 
and Table ] 
15. Abbreviations for independent variables: DA = 
drainage area; 
LA = limestone 
area; NC = Number of caves. 
Endemic terrestrial species (dependent variable) is abbreviated ET. 
Percent 
Dependent 
Independent 
Variance 
Variable 
Variable 
Explained 
P 
ET 
DA 
0.0 
N.S. 
ET 
LA 
0.6 
N.S. 
ET 
NC 
52.0 
>0.95 
In ET 
In DA 
17.3 
N.S. 
In ET 
In LA 
17.7 
N.S. 
In ET 
In NC 
63.9 
>0.95 
The second pattern is exemplified by species that do not appear to 
have evolved directly from epigean ancestors but instead were probably 
derived through lineages from ancestors already living in subterranean 
groundwater habitats. These species have no known surface congeners 
and belong to phylogenetically very old groups. Taxa corresponding to 
this pattern are crangonyctid amphipods ( Bactrurus and Stygobromus), 
cirolanid isopods (Antrolana), and possibly planarians ( Sphalloplana ). 
Alloeocoelid and lumbriculid worms are still too poorly known 
taxonomically and ecologically in North American subterranean waters 
to identify them with either of the two patterns (see Carpenter 1970a, 
Cook 1977). Common troglophiles, such as Phagocata spp., Fontigens 
orolibas, Gammarus minus, and Cambarus bartonii, are found in both 
epigean and hypogean waters, and the cave populations probably 
represent recent invasions of subterranean habitats. However, as indi- 
cated below, F. orolibas and G. minus (Form I) could be special cases. 
