PHENOTYPIC PLASTICITY OF DAPHNIA LIFE-HISTORY TRAITS IN RESPONSE TO PREDATOR KAIROMONES - GENETIC-VARIABILITY AND EVOLUTIONARY POTENTIAL

Cladoceran populations can respond to changing predation regimes by a phenotypical response as well as by shifts in genotype frequencies. In this study, we investigated the phenotypic plasticity exhibited by li fe history traits of D. galeata in response to the presence of predato r kairomones, as well as the extent to which natural selection may act on these traits and their phenotypic plasticity. In a life-table expe riment, seven clones of a natural D. galeata population were subjected to kairomones from fish (Perca), from an invertebrate predator (Chaob orus) or a mixture of both. Life history traits were affected by the k airomones of both predators, but effects of Chaoborus were neutralised by Perca in the kairomone mix. No apparent trade-off was found betwee n growth-and reproduction related traits: although daphnids from the C haoborus treatment grew faster than daphnids from the other treatments , no reduction in the reproductive output was observed. Broad-sense he ritabilities were found to be relatively high for some life history tr aits (size at maturity, neonate size, number of neonates) as well as f or the phenotypic plasticity response of these traits. This reflects t he evolutionary potential of life history traits and their phenotypic response to predator kairomones in the D. galeata population.