Post-glacial dispersion and Pleistocene refugia of two stoneflies (Plecoptera) inhabiting eastern North America

Aquatic insects have been studied only sparingly in relation to post-glacial recolonization in North America. Aquatic insects are great model organisms for this purpose because they are widely distributed, their distributions are comparatively well known, and because they can often be collected in abundance. H. H. Ross and W. E. Ricker in 1971 provided post-glacial dispersal hypotheses for several winter-emerging stonefly species in the genus, Allocapnia (Capniidae) that inhabit eastern North American. Their hypotheses implied multiple refugia, the existence of the Wisconsinan Till Plain as a prominent barrier to dispersal, and the use of bluff streams of major rivers as corridors into once glaciated areas. Advances in molecular biology allow us to rigorously test some of these hypotheses. Two stonefly species, the winter stonefly A. granulata (Claassen) (Capniidae), and the summer emerging Acroneuria frisoni (Stark & Brown) (Perlidae) were sampled from throughout their range for 35 and 20 populations, respectively. We sequenced nearly the entire mitochondrial Coenzyme Oxidase I (COI) gene for both species. Haplotype distributions strongly support at least two refugia for both species (S Appalachians and Ozarks). They also demonstrated that the Till Plain did not pose a barrier to their dispersal northward. The relative contribution of each of these refugia and possible routes of dispersal will be discussed.