Inter- and Intra-Specific Analyses of the Food Niches of Two Sympatric Species of Erpobdellidae (Hirudinoidea) in Alberta, Canada

Abstract

The feeding of Nephelopsis obscura Verrill and Erpobdella punctata (Leidy) was investigated in Bruce Lake, Alberta, Canada, using specific rabbit antisera against Cladocera/Copepoda, Chironomidae, Oligochaeta, Amphipoda and Gastropoda. At the species level, prey utilization curves, niche breadth and evenness values for N. obscura and E. punctata showed no significant differences, apart from the absence of Gastropoda in the diet of E. punctata. For any given month Chironomidae, Oligochaeta and Amphipoda dominated the diet of both species; temporal differences in prey utilization did occur. Both intra- and inter-specific resource partitioning occurred as a function of differential weight class utilization of prey. Food niche overlap occurred through the spring, summer and autumn but the probability for interspecific competition was highest in the late summer and early autumn when niche breadth decreased.