Tuesday, June 5, 2007

Historic Assemblage, Range Loss and Extirpations of Acroneuria Stoneflies (Plecoptera) in Illinois

Lynn Fennema, School of Life Sciences, University of Illinois, Champaign, IL 61820 and R. Edward DeWalt, Illinois Natural History Survey, 1816 S Oak St., Champaign, IL 61820.

Historic Acroneuria (Plecoptera: Perlidae) specimens from the Illinois Natural History Survey and from other museums were re-evaluated and their taxonomy updated. The historic assemblage consisted of six species. Acroneuria abnormis, A. evoluta, and A. perplexa originally inhabited the largest streams, including the Mississippi and the Ohio rivers, with A. abnormis also being found in somewhat smaller rivers. Acroneuria internata, A. frisoni, and A. filicis inhabited medium to small rivers and sometimes occurred in smaller streams to 5 m wetted width. Extirpations include A. internata and A. perplexa, while all other species have experienced severe range reductions.  Acroneuria frisoni, was widespread in Illinois, but now is relegated to extreme southern Illinois in the Shawnee National Forest. Most losses occurred in the late 1940s—1960s and resulted from agricultural modification, urbanization, and probably from indiscriminant pesticide usage.  Re-evaluation of the distribution of these species allows Illinois to add them to lists of species of concern and allows aquatic biologist to know the extent of losses from pre-settlement times.