COMPETITION IN NATURAL-POPULATIONS OF DAPHNIA

I investigated the competitive relationships between two species of Da phnia, D. galeata and D. cucullata, and their interspecific hybrid. Th e term hemispecific competition was introduced to describe competition between parental species and hybrids. In eutrophic Tjeukemeer both pa rental species were found to compete with the hybrid, whereas competit ion between D. galeata and D. cucullata seemed limited. Although the e ffect of competition on life history traits of daphnids may be profoun d, the influence of the competitors on the seasonal dynamics of the Da phnia species seems limited.