144 
John R. Holsinger and David C. Culver 
In the Entomobryinae, Christiansen (1981, 1982) postulated several 
evolutionary lineages for each genus. In Sinella , 5. hoffmani is placed in 
a lineage with the troglophile S. barri. In Pseudosinella , P. hirsuta, P. 
orba , and P. argentea (a troglophile) are each placed in a separate 
lineage. 
To account for the extensive range of P. hirsuta (parts of Alabama, 
Georgia, Kentucky, Tennessee, and Virginia), Christiansen and Culver 
(1968) and Christiansen (1982) postulated a process they termed “parallel 
speciation,” which was envisioned as having resulted from the invasion 
of caves by an ancestor over a wide geographic area, followed by 
independent parallel development of the same morphology in separate, 
physically isolated lineages. The end products would resemble each 
other so precisely in behavior, morphology, and ecology that they could 
be called the same species. According to this interpretation, P. hirsuta 
would have to be regarded as a complex of several biological (sibling?) 
species. Populations in the study area, although apparently morpholo- 
gically indistinguishable from those farther west in Kentucky and middle 
Tennessee, are probably genetically distinct. Christiansen (1982) 
interprets the rather wide and discontinuous range of S. hoffmani as 
either the result of parallel speciation or representative of the vestiges of 
a previously continuous range. However, both P. hirsuta and S. hoffmani 
have been found outside caves on rare occasions, and the possibility 
that their wide ranges have resulted in part from dispersal between karst 
areas through shallow underground compartments or similar endogean 
habitats cannot be dismissed. 
According to Christiansen (1982), the evolution of P. orba , which 
has a more limited geographic distribution than either P. hirsuta or S. 
hoffmani, has probably resulted from the single invasion of caves by a 
putative ancestor and subsequent subsurface dispersal to the present 
limits of its range. In the genus Arrhopalites, Christiansen (1982) 
suggests that the troglomorphic A clarus, recorded from caves in both 
the Ozarks and the Appalachian Valley, might be the product of parallel 
speciation at least twice from a common, widespread ancestor. 
The dipluran genus Litocampa contains 32 species worldwide; a 
majority (20) inhabit caves in the United States, and all are troglobites 
(Ferguson 1981a, 1981b). The wide geographic distribution of the genus 
(viz., parts of Africa, Europe, and North and South America), combined 
with retention of certain characters judged to be primitive for the order, 
has led Ferguson (1981a, 1981b) to suggest that its origin may predate 
the breakup of the supercontinent Pangaea in the Mesozoic. The 
absence of epigean congeners anywhere in North America suggests that 
troglobitic species of Litocampa are probably relatively old cavernicoles. 
Moreover, based on the richness of species and number of endemics in 
the southern Appalachian region, Ferguson has suggested this area as a 
