DIVERSITY OF STREAM-LIVING INSECTS IN NORTHWESTERN PANAMA

Data on species richness and diversity of aquatic insects are presented for 42 streams from four drainage areas in northwestern Panama. 189 taxa were collected, many of which are undescribed species. Nearly 45% of the taxa were found in only one of the drainage areas. Diversities, as measured by alpha of the log series, and similarities, measured by number of expected species shared (NESS), were calculated for 25 sites in the four drainages. Diversities varied widely between streams and broadly overlap alpha diversities found in temperate streams. There was no significant correlation between insect diversity and altitude in the Panamanian streams. Similarity of Ephemeroptera faunas among streams showed two patterns: a relatively homogeneous mountain stream fauna in localities above 300 m elevation, and a much more heterogeneous fauna in lowland streams below this altitude. These patterns were less clear for other aquatic insect orders. The results suggest that variation among streams within a tropical region is as important as any "latitudinal gradient" between tropical and temperate streams.