Invertebrate Cave Fauna 
135 
the study area belong to higher taxa that are simultaneously well 
represented by cryptozoic, epigean species living in the cool, moist litter 
microhabitats of montane forests of the Appalachians. Furthermore, the 
greater Appalachian region, because of its rich diversity of both habitats 
and biota, has been suggested as the site of origin for much of the 
ancestral stock of the terrestrial troglobite fauna of the entire eastern 
United States (Peck and Lewis 1978). 
The widely accepted model for the origin of terrestrial troglobites 
in temperate regions of the Northern Hemisphere is based on climatic 
fluctuations in the Pleistocene (Barr 1967a, 1968, 1973, 1985; Poulson 
and White 1969; Peck 1981b; Culver 1982). According to this hypothesis, 
during periods of glacial maxima, the cold, moist areas lying south of 
glaciation, such as the southern Appalachians, would have provided a 
suitable environment for the extensive distribution of a cryophilic 
endogean fauna. Both caves and ecologically suitable surface habitats 
would have been colonized by this fauna. During interglacial periods, 
when the regional climate became warmer and drier, many elements of 
this fauna would have become extinct at the surface, especially at low 
elevations, but other elements would have survived in caves and at high 
elevations in cool-mesic forests. The extinction of surface populations at 
low elevations during interglacials would have resulted in the genetic 
isolation of founder populations in caves, because migration and gene 
exchange between epigean and hypogean populations would have been 
eliminated in many karst areas. Ultimately this series of events would 
have led to the evolution of troglobitic species, depending on the length 
of time of physical isolation underground and whether or not certain 
populations subsequently reinvaded suitable surface habitats during 
succeeding glacial advances (c.f., the taxon cycle of Peck 1980). 
Eventually, however, isolation was completed for many cave populations. 
Since the onset of the Pleistocene, there has probably been a sequence 
of invasions and colonizations of caves by preadapted, troglophile 
ancestors and concomitant extirpations of closely related epigean 
populations. The detailed evolutionary history of any troglobitic group, 
however, must be relatively complex, because, as Peck (1980) suggests, 
many groups have probably passed through a taxon cycle that first 
involved isolation of populations in caves, followed by expansion into 
epigean habitats and, then, ultimately by isolation again in caves during 
a succeeding interglacial. 
One of us (Culver 1982) recently reviewed the evidence in favor of 
the Pleistocene climatic-effect paradigm and concluded that, although 
indirect, the evidence supporting the hypothesis was strong. Nonetheless, 
this hypothesis has recently been questioned by several workers. Based 
on studies of the newly discovered troglobitic fauna of Hawaiian lava 
caves, Howarth (1980, 1981) suggested that troglobitic organisms have 
