LEECHES (ANNELIDA, HIRUDINEA) IN THE EXPERIMENTAL LAKES AREA, NORTHWESTERN ONTARIO, CANADA - PATTERNS OF SPECIES COMPOSITION IN RELATION TOENVIRONMENT

Canonical correspondence analysis (CCA) was used to examine the distri bution of leeches (Annelida: Hirudinea) in 18 lakes at the Experimenta l Lakes Area (ELA). Leech community composition was best described by an ordination incorporating alkalinity, primary productivity, and lake area. In general, highest species richness occurred in small, eutroph ic lakes whereas lowest richness was recorded in medium to large lakes with low productivity. Contrary to results for some other taxa, lake pH was not a dominant variable, describing only a small amount of vari ance in the species-environment relationship.