Invertebrate Cave Fauna 
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Barr (1965, 1967a, 1967c, 1968, 1973, 1981a, 1985), on the other 
hand, based on his studies on the geographic distribution and ecology of 
troglobitic trechine beetles, has made a convincing case for the 
Pleistocene climatic-effect model. Barr (1967b, 1968) has also made a 
strong argument for the allopatric speciation process in the evolution of 
troglobites and has suggested that after isolation of a founder population 
in a cave or series of interconnected caves, following the extinction of 
epigean ancestors, the newly isolated cave colony will pass through a 
period of lowered genetic variability (genetic bottleneck). Moreover, if 
the colony survives, an extensive genetic reorganization will result in a 
reconstructed epigenotype, the end point of which is a well-adapted 
troglobite. Genetic, studies by Sbordoni et al. (1981) on cave crickets in 
southern Europe tend to support the bottleneck effect in the evolution 
of cave species, but the degree to which an epigenotype is reconstructed 
in the evolution of a troglobite remains unclear. It is entirely possible, 
however, that genetic differences between troglobites and epigean 
congeners have been overstressed, despite the prominent regressive 
features that develop almost universally in highly specialized cavernicoles. 
It is beyond the scope of this paper to debate the pros and cons of 
allopatric versus parapatric speciation. But it should be pointed out 
that, whereas allopatric speciation is still favored over parapatric 
speciation for most groups of organisms, a rather strong case has been 
made for parapatric speciation (sensu Bush 1975, Endler 1977) in some 
groups under certain conditions, and it cannot be ruled out as a possible 
mode of evolution for some troglobites. 
Trechine beetles of the genus Pseudanophthalmus are taxonomically 
the most numerous and thoroughly studied terrestrial troglobites in the 
study area and therefore provide good data for zoogeographic analyses. 
According to Barr (1981a, 1981b), ancestors of troglobitic species 
presently living in caves of both the Appalachian Valley and Ridge and 
the Interior Low Plateaus probably originated in upland forests of the 
Appalachian Plateau and spread out under periglacial climates. Caves 
were colonized at the beginning of interglacial periods. The ancestors 
were probably edaphobites already strongly preadapted for a cave 
existence. An earlier hypothesis by Jeannel (1949) suggested that 
ancestors spread out from an interglacial refugium in the Unaka 
Mountains along the Tennessee-North Carolina border, but Barr has 
made a more convincing case for an Appalachian Plateau center of 
distribution. Barr’s theory is based principally on dissimilarities of 
species on opposite sides of the Appalachian Plateau, the increased 
richness of species closer to the plateau front in the Appalachian Valley, 
and the occurrence of a single edaphobitic species ( Pseudanophthalmus 
sylvaticus ) in the Plateau and not in the Unakas. The Unaka hypothesis 
was not discarded altogether by Barr, however, since, as he points out, 
distributions of the engelhardti and petrunkevitchi groups are not 
