126 
Gary W. Dickson, et al. 
I 
0.85 0.90 0.95 1.00 
i 1 1 1 
Roadside No.l 
— POOL 
Gailohan No. 2 
— STREAM 
Sweet Potato 
— POOL 
Molly Wagle 
— POOL 
Cope 
STREAM 
Spangler 
STREAM 
(185 0.90 095 LOO 
Fig. 2. Dendrogram of C. antennatus populations based on genetic similarity values derived 
from eight loci. Scale is in units of genetic identity, I. Cophenetic correlation equals 0.79 
DISCUSSION 
In addition to measurements of physical and chemical parameters, 
studies of troglobitic organisms have yielded biological evidence which at- 
tests to the relative environmental stability of cave systems. In general, 
troglobitic species exhibit K-selected population characteristics including 
late maturity, low reproductive rates, large size at hatching and increased 
longevity (see reviews in Vandel 1965; Dickson and Holsinger, in press). 
Population characteristics of this type have been associated with 
relatively stable (i.e. predictable) habitats (MacArthur and Wilson 
1967). Of these characteristics, perhaps the most remarkable is the ex- 
tremely long life span reported for various troglobites (Poulson 1964; 
Cooper 1975; Dickson and Holsinger, in press). Increased longevity has 
also been described in deep-sea organisms (Turekian et al. 1975; 
Engemann 1978). 
From the results of the present investigation and previous studies on a 
number of different cave species (Table 3), genetic variability does not ap- 
pear to be substantially reduced in populations inhabiting subterranean 
