Clonal variation in the survival and reproduction of Daphnia pulicaria under low-food stress

1. Survivorship and reproductive parameters of eight Daphnia pulicaria clones were evaluated in a life-table experiment under four dietary regimes ranging from food limitation to complete food deprivation. 2. D. pulicaria exhibited both diet-independent interclonal differences and genotype-environment interactions in life-span. 3. Reproduction ceased entirely or nearly so under the three treatments with lowest food availability. Under life-long food limitation, differences between clones were evident in clutch sizes and age at first reproduction. Some clones produced ephippia at a markedly higher frequency than others under food-limiting conditions. 4. For most of the life-history traits evaluated, within-lake variation among clones exceeded differences between the two lake populations they represented. 5. Intraspecific variations in response to periods of food deprivation and to extended quantitative or qualitative food-limitation could affect the clonal composition of Daphnia populations. They are therefore of potential importance in determining the effect of altered phytoplankton assemblages on zooplankton communities.