Phenotypic plasticity of Daphnia life history traits: the roles of predation, food level and toxic cyanobacteria

Abstract

1. We studied the life history responses of Daphnia pulex under different biotic conditions. In a factorially designed experiment, we tested the impacts of water conditioned by the invertebrate predator Chaoborus, low and high food level (10 000 and 100 000 Scenedesmus cells ml–1), and exposure to toxic Microcystis (5000 cells ml–1) on twelve D. pulex clones originating from different habitats. Our aim was to compare the phenotypic plasticity of different clones, and to study the interactions among biotic factors.2. Individuals cultured in Chaoborus‐conditioned water started to reproduce at a larger size than individuals cultured in water not conditioned by the predators. We found interactions between food level and Chaoborus‐conditioned water on age at first reproduction and total offspring number. In addition, the impact of the Chaoborus treatment on the size at first reproduction was reduced by Microcystis exposure.3. Clonal differences were found in the degree of phenotypic plasticity of different life history traits. However, there was no obvious connection between the original habitat of the clone and the degree of plasticity.