Species Diversity of Black Flies (Diptera: Simuliidae) in Relation to Stream Size Submitted

Abstract

Black flies have been studied extensively because they: have an essential world-wide distribution, require a blood meal from humans and other animals to reproduce, transmit blood-bound diseases, have diverse sibling species differentiated by chromosomal rearrangements associated with sex and act as an important food source in fresh water ecosystems. Reproduction is universally tied to fresh water streams in which eggs, larvae, pupae and adults develop. Despite the large number of studies of black fly ecology, genetics and parasitology, essentially nothing is known about factors that determine species diversity of black flies at specific locations. I tested the hypothesis that large streams would have greater species diversity of black flies than medium-sized or small streams by collecting black fly larvae from six streams in west-central Montana (Missouri River and Yellowstone River (large streams); Little Prickly Pear Creek and the Gallatin River (medium-sized streams) and Ten Mile Creek and Camp Creek (small streams) at two-week intervals throughout the summer of 2001. Although I have only two replicates for each of the three size categories, the highest species diversity was observed in medium-sized and small streams and not in large streams as I had predicted. Possibly, small and medium sized streams provide more diverse microhabitats throughout the year than do large streams. Although all species of black fly in this study had been previously described for the province of Alberta, Canada, a new chromosomal cytotype designated, Simulium arcticum IIL-15, was described from both the Yellowstone and Gallatin rivers.