LATITUDINAL CONSIDERATIONS FOR CHOICE OF SAMPLING PROTOCOL FOR ASSESSING THE SPECIES RICHNESS OF LOTIC CHIRONOMIDAE USING PUPAL EXUVIAE.

W.P. Coffman. Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260

Collection of pupal exuviae is gaining recognition as an efficient and accurate means to determine species composition of lotic Chironomidae. The success of such assessments is largely determined by sampling protocol (timing, number and size of samples). For maximum efficiency, it is necessary to determine periods of the year for intense (high frequency) or relaxed (low frequency) sampling effort, leading to sampling schedules that detect the most species per unit effort. Efficient sampling schedules are strongly affected by latitude. Because of the short temporal window in which emergence place from high latitude streams, sampling protocols should include frequent samples from "ice-out" to "ice-on." Although species of mid-latitude streams have longer periods of emergence, the emergence periods for particular species are still largely regulated by physical (e.g., temperature) and biological (food supply for larvae) cues. Sampling schedules should reflect the temporal partitioning of emergence of species and include intense sampling in the late winter/early spring through early summer. In low latitude streams, physical and biological environmental cues are less significant, with many species having emergence periods spaced through the entire year. Consequently, the number of species per sample is often quite large, and samples from a few times spaced during the year probably will detect a large part of the community.