244 
Psyche 
Discussion 
[Vol. 93 
The patterns of variation described here for N. tellkampfi provide 
a basis for understanding some of the factors which cause genetic 
differentiation in cave limited species. Barr (1979b) suggested that 
three different patterns of gene flow were indicated by the morpho- 
logical and geological data on the four subspecies. These include: (1) 
no gene flow ( henroti with either tellkampfi or viator ); (2) very 
limited gene flow ( meridionalis with tellkampfi ); and, (3) moderate 
gene flow (tellkampfi with viator). Initially the biochemical data 
seem to support only pattern (2) with population F clearly contain- 
ing meridionalis X tellkampfi hybrids and with other meridionalis 
and tellkampfi populations examined in this study showing no bio- 
chemical evidence of hybridization. Thus, the morphological data 
(Barr, 1979b) and now the biochemical data suggest that hybridiza- 
tion is restricted to a very narrow geographic area. 
The allozyme data directly support only part of pattern (1). The rela- 
tively large genetic distance between henroti and viator (D = 0.289) 
and the lack of any biochemical, as well as morphological (Barr, 
1979b), evidence of hybridization support the assertion that 
the Hart Co. Ridge is acting as a complete barrier to gene flow 
between these two subspecies. The large genetic similarity between 
henroti and tellkampfi (S > 0.96) does not lend support to the 
conclusion that these two subspecies are also extrinsically isolated 
from each other. However, allozyme studies on the scavenger beetle 
P. hirtus (Laing et al., 1976) show that a population north of the 
Hart Co. Ridge has a genetic similarity (I) of approximately 0.75 
with two populations south of the Ridge in caves GO and RB, which 
are also occupied by nominate tellkampfi. Further, the Hart Co. 
Ridge coincides with the southern range limit of Orconectes inermis 
(Decapoda: Astacidae) and the northern range limit of O. pelluci- 
dus, two species of troglobitic crayfish whose ranges are almost 
completely separate (Hobbs and Barr, 1972). Thus the evidence for 
the Hart Co. Ridge as a dispersal barrier is overwhelming. 
The close genetic similarity between henroti and tellkampfi is 
consistent with Barr’s (1979b) supposition that all four subspecies of 
N. tellkampfi are descended from a common ancestral stock that 
became isolated in caves in the southern portion of the present 
range. Barr argues that henroti was derived from a peripheral popu- 
lation of nominate tellkampfi which penetrated north of the Hart 
