Life history variability in response to temperature and Chaoborus exposure in three Daphnia pulex clones

Abstract

In a 21-day life table experiment, we studied the role of temperature, exposure to Chaoborus obscuripes, and their interaction on life history parameters and neck spine development in Daphnia pulex. We used three D. pulex clones collected from different ponds in southwestern Finland. In these ponds, temperature, predation pressure, and the clonal composition of Daphnia populations may vary substantially. Each clone was exposed to Chaoborus-conditioned water or control water at 16 and 20°C. Predator exposure and temperature affected significantly age and size at first reproduction and the total number of offspring in Daphnia. Interaction between predator exposure and temperature approached significance for the age at first reproduction, and the interaction between predator exposure and clone was significant for the same trait. Temperature interacted with clonal origin for all reproductive parameters studied. All three clones showed no or only weak morphological responses to Chaoborus. This indicates that the life history changes observed are independent of neck spine formation and may be adaptive in the presence of invertebrate predation.