BIODIVERSITY AND LONGITUDINAL COMPOSITION OF CHIRONOMIDAE IN THE ST. CROIX RIVER

Leonard C. Ferrington, Jr., Department of Entomology & Water Resources Sciences Program, University of Minnesota, Saint Paul, MN

The biodiversity and longitudinal composition of Chironomidae were determined using monthly collections of surface-floating pupal exuviae at 17 sample sites spanning more than 170 river miles, from April through October 2007. At least 164 species classified in 84 genera and five subfamilies were documented and their emergence dates determined. Nested-subsets analyses were performed on presence-absence matrices for individual sample sites, and pair-wise similarities were calculated for adjacent sites, to determine if transitions in longitudinal composition are better-described with continuous or discontinuous models of community assembly. However, it appears that neither type of model applies well across the geographic scale encompassed in this project.