Niche overlap of sympatric Blepharicera larvae (Diptera : Blephariceridae)from the southern Appalachian Mountains

The southern Appalachian Mountains are home to the greatest diversity of Bl ephariceridae (Diptera) in North America, with 13 Blepharicera Macquart spe cies inhabiting the region. Sympatric Blepharicera species seem to occupy a common ecological niche, in contradiction to the competitive exclusion pri nciple. Instar IV Blepharicera larvae were studied to determine whether die tary differences facilitate coexistence of sympatric species. Diatom assemb lages of Blepharicera diets, total diatom biovolume ingested, and similarit y between diatom assemblages of larval diets and the forage base were exami ned. Dietary characteristics were compared among Blepharicera species withi n and between discrete microhabitats at 3 sites in southern Appalachia. Dat a showed broad dietary overlap among species that co-occurred in the same m icrohabitat and strong microhabitat effects on larval dietary assemblages. In addition, several species ingested disproportionately greater biovolumes of small, adnate and prostrate diatom species compared to their availabili ty on the substratum. Sympatric Blepharicera species may not partition food resources where spatial overlap is most acute.