146 
James L. Gooch and Jeffrey S. Wiseman 
genetic differentiation among demes. This is true of the karst region 
where the ecotypes were first described (Gooch and Hetrick 1979) and in 
the central Pennsylvania localities studied here (Gooch and Golladay, in 
press). The genetic investigations were done on three polymorphic 
allozyme loci. Genetic patterns have not been found to correspond to 
habitats or ecotypes and will not be discussed here. They do clearly in- 
dicate that the most geographically isolated populations often carry 
atypical alleles in high frequencies, either due to local adaptation or 
genetic drift, and that demes linked by likely avenues of migration have 
not undergone as much genetic differentiation. 
James Creek, with its aberrant ratio of female/male appendage 
lengths, is probably an example of a deme that has evolved mor- 
phological characters in partial isolation from other populations. 
Greenland Gap, on the other hand, apparently has been prevented from 
acquiring habitat specific characters due to strong gene flow from other 
habitats. The mid-Appalachian area is an environmental mosaic of 
epigean, intermediate, and hypogean habitats. The result in G. minus has 
been the evolution of markedly differentiated ecotypes. Streams and 
divides, however, provide clear avenues and barriers to migration, 
leading to highly anisotropic gene flow. Superimposed on ecotypic varia- 
tion and sometimes discordant with it is the local differentiation of 
isolated demes. Ecotypic distinctions are further modified by gene flow 
among demes that are open to migration. 
ACKNOWLEDGMENTS.— Jhh research was carried out during 
the tenure of NSF-URP Grant No. SPI-7827183, which provided a sti- 
pend to the junior author. Funding under NSF Grant No. DEB75-03302 
AOl to the senior author supported the initial research. We are indebted 
to Drs. Gerald A. Cole, John R. Holsinger, and William R. Rhodes for 
their constructive comments on earlier drafts of the manuscript. 
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