Genetic diversity vs geographic distribution of five congeneric caddisflies

We compared the genetic structure and diversity offive Cheumatopsyche (Trichoptera:Hydropsychidae) species from Upper Three Runs Creek inSouth Carolina to analyze the relationship betweengenetic variability and potential gene flow (i.e.,geographic distribution) in a group of loticmacroinvertebrates. Among these species is an endemicto the stream (Cheumatopsyche richardsoni), asoutheastern U.S.A. endemic (C. edista), andthree widely distributed species (C. pasella,C. pettiti, and C. pinaca). Usingcellulose acetate plates, we reliably scored 19presumptive allozyme loci for each species. C. richardsoni and C. pettiti were the leastgenetically variable taxa, C. pasella and C. pinaca the most, and C. edista fell inbetween. Therefore, unless this C. pettitipopulation is not representative of the species ingeneral, the genetic diversity of C. richardsoniand C. edista fall within the range exhibited byother congeners. In turn, each species’ geneticdiversity is evidently not correlated to its relativegeographic distribution. Four species (all but C. pettiti) had moderate to high proportions ofpolymorphic loci in Hardy-Weinberg disequilibria, thecause of which is likely one of three factors: (1) eachspecies experiences disruptive selection, (2) weinadvertently sampled adults from more than onegenetically distinct stream population, or (3) eachspecies is divided into partially reproductivelyisolated subpopulations within the stream. This revised version was published online in July 2006 with corrections to the Cover Date.