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[Vol. 93 
ephemeral. Thus, stochastic events may have a greater influence on 
the genetic characteristics of local P. hirtus populations than on 
those of N. tellkampfi. In fact, genetic variability in local P. hirtus 
populations (P = 0.154; H = 0.048 (Laing et al., 1976)) appears to 
be about half that of local N. tellkampfi populations (P = 0.302; 
H = 0.094). Further, the average Nei index between local P. hirtus 
populations in the range of N. t. tellkampfi is I = 0.874 (Culver, 
1982), whereas the average I between local nominate tellkampfi 
populations is 0.981. Thus, if ecological differences influence genetic 
patterns of similarly cave dependent species, the effects appear to be 
manifested at the level of local populations. 
Acknowledgments 
We would particularly like to thank Dr. Thomas C. Barr, Jr. for 
valuable discussions throughout the study, including a critical 
review of the manuscript. In addition, Dr. Barr kindly provided us 
with locations for several of the cave sites and in one case (ST site) 
provided us with material for electrophoresis. We would also like to 
acknowledge and thank Curtis Meininger for field assistance and 
useful discussions and Kevie Vulinec for drafting the figures. The 
National Part Service, Mammoth Cave National Park, KY, kindly 
provided access to several of the sites used in this study. This 
research was partially supported by a National Speleological 
Society Research Grant to GDB and by grants from the American 
Philosophical Society (Penrose Fund No. 8718) and the National 
Science Foundation (DEB-8202273) to TCK. 
Summary 
An understanding of patterns of geographic variation is impor- 
tant in interpreting evolutionary relationships between closely sim- 
ilar taxa and in inferring levels of gene flow between geographic 
populations. For obligate cave dwelling (i.e., troglobitic) species, 
dispersal and gene flow are restricted to subterranean routes. Thus, 
the interconnectivity of caves and the presence of geological barriers 
become important factors in determining the geographical distribu- 
tion and the degree of gene flow among populations of troglobitic 
species. 
Neaphaenops tellkampfi , a troglobitic trechine beetle, has the 
most extensive geographic range and is one of the most abundant of 
