Reproductive strategy as population density varies in Daphnia magna (Cladocera)

Abstract

SUMMARY In this study an experiment was carried out to test whether Daphnia magna (Cladocera) changed its reproductive strategy in response to varying population density but constant food supply. As population density increased there was a reduction in the age at which females reproduced. Early reproduction was offset by smaller body length and clutch size (number of eggs per female) relative to later reproducing females grown at lower population densities. This pattern was interpreted as a strategy carried out by females to reduce the time at which they release their offspring. One potential advantage of early reproduction is to reduce the risk of severe food limitation for neonates born during a period of rapid population increase.