SREL Reprint #2271

Genetic diversity vs. geographic distribution of five congeneric caddisflies

Gordon R. Plague1,2 and J Vaun McArthur1

1Savannah River Ecology Laboratory, University of Georgia, P.O. Drawer E, A iken, SC 29802, USA
2Department of Entomology, University of Georgia, Athens, GA 30602, USA

Abstract: We compared the genetic structure and diversity of five Cheumatopsyche (Trichoptera: Hydropsychidae) species from Upper Three Runs Creek in South Carolina to analyze the relationship between genetic variability and potential gene flow (i.e., geographic distribution) in a group of lotic macroinvertebrates. Among these species is an endemic to the stream (Cheumatopsyche richardsoni), a southeastern U.S.A. endemic (C. edista), and three widely distributed species (C. pasella, C pettiti, and C. pinaca). Using cellulose acetate plates, we reliably scored 19 presumptive allozyme loci for each species. C richardsoni and C pettiti were the least genetically variable taxa, C. pasella and C. pinaca the most, and C. edista fell in between. Therefore, unless this C. pettiti population is not representative of the species in general, the genetic diversity of C. richardsoni and C. edista fall within the range exhibited by other congeners. In turn, each species' genetic diversity is evidently not correlated to its relative geographic distribution. Four species (all but C. pettiti) had moderate to high proportions of polymorphic loci in Hardy-Weinberg disequilibria, the cause of which is likely one of three factors: (1) each species experiences disruptive selection, (2) we inadvertently sampled adults from more than one genetically distinct stream population, or (3) each species is divided into partially reproductively isolated subpopulations within the stream.

Keywords: Genetic variability, endemism, heterozygote deficiency, Hydropsychidae, Cheumatopsyche, stream

SREL Reprint #2271

Plague, G.R. and J.V. McArthur. 1998. Genetic diversity vs. geographic distribution of five congeneric caddisflies. Hydrobiologia 362:1-8.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).