Geographic Variation in the Cave Beetle, Neaphaenops Tellkampfi (Coleoptera: Carabidae)

More than 200 species of cave limited (i.e., troglobitic) trechine carabid beetles are known from caves of the eastern United States (Barr, 1979b, 1981). These species are generally considered to be derived from ancestral surface species which were widespread during the cold, moist climates associated with glacial maxima (Barr, 1968). Subsequent warming and drying of these regions, as glaciers retreated, led ultimately to the extirpation of surface populations, with only some of the cave limited stocks surviving. Available evidence suggests that for trechines cave isolation is irreversible (Barr, 1968, 1979a). Therefore, geographic spread of and gene flow in troglobitic trechines will be restricted to subterranean routes (Barr, 1968). The interconnectivity of caves and the presence of geological barriers (e.g., noncavernous strata and large rivers) become important factors in determining the geographic extent of and degrees of gene flow within these troglobitic taxa. In extensive and highly continuous limestone cave systems, such as those of the Mississippian plateaus, interpretation of evolutionary relationships between closely similar taxa becomes especially complicated (Barr, 1979b). One question which arises is whether such taxa represent multiple isolations of a common surface dwelling ancestor or are the product of more recent divergence in a common troglobitic ancestor. Even when the latter scenario appears to be the case, divergence may only involve subtle, although generally consistent, differences in minor morphological characters. Thus, inferences about such factors as the amount of gene flow, if