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James L. Gooch and Jeffrey S. Wiseman 
with reduced eyes and elongate antennae, and Hubricht (1943) further 
described an intermediate type between the surface and deep cave forms. 
Holsinger and Culver distinguished three intergradational forms or 
ecotypes, each associated with a specific habitat. Form I amphipods have 
considerably reduced eyes, bluish body color, and elongate appendages, 
and are confined to a few large cave systems in isolated karst areas of 
Virginia and West Virginia. Form II individuals have slightly reduced 
eyes, bluish bodies, and slightly lengthened appendages, and occur widely 
in mid-Appalachian caves. Form III amphipods are brownish and ro- 
bust, with large eyes and relatively shorter appendages, and are found in 
surface habitats throughout the species’ range. The three forms occur in 
proximity in the karst areas of southeastern West Virginia. Many popula- 
tions there are sharply genetically distinct, genetic breaks frequently coin- 
ciding with divides between karstic sub-basins (Gooch and Hetrick 1979). 
The present study is limited to Form III populations and inter- 
gradational Form II, which comprise the great majority of G. minus 
populations. We used, among others, the labile eye and appendage 
characters of the Holsinger and Culver study. The nine populations oc- 
cupied habitats which we rank ordered from most open or epigean to 
least open (or marginal hypogean). Measurements were taken on each 
population to determine the degree to which ecotype typifying 
morphology conformed to the habitat scale. Strong conformance as 
shown by similar rank order would indicate a predominant influence of 
environmental factors related to habitat openness. Weak conformance 
would indicate that other factors such as local adaptation to biotic or 
physical conditions or the interplay between genetic drift and gene flow 
strongly influence morphology. 
METHODS AND MATERIALS 
Samples of Gammams minus were taken using a Surber sampler and, 
on highly irregular bottoms, a dip net. From each sample 50 sexually 
mature individuals, 25 of each sex, were chosen at random. The following 
measurements were made on one side, indiscriminantly right or left, on 
each individual: 
(1) Packing density and regularity of the eye. The facets bordering 
the eye may be tightly and regularly packed or loose and irregular, 
producing, respectively, a border that is smooth or one that is ragged and 
embayed. Holsinger and Culver treated this character in some detail and 
depicted eye shape in typical members of the three habitat forms (their 
Fig. 3). The latitude of regularity was much less in our populations. Eyes 
were scored on an estimated ordinal scale of high, intermediate, and low 
density and regularity. 
(2) Lobe orientation. The eyes of typical epigean G. minus are short 
reniform with the lower lobe usually broader than the upper (Cole 1970). 
In some individuals the lobes are equal or the upper lobe is broader. Eyes 
