Neutral markers, ecologically relevant traits, and the structure of genetic variation in Daphnia

Zooplankton, Daphnia in particular, are increasingly used as model organisms to investigate general evolutionary biological questions. I here discuss some recent insights into the patterns and processes determining genetic diversity within and genetic differentiation among natural populations of cyclically parthenogenetic Daphnia. I focus on three aspects: (1) the interplay of phenotypic plasticity and genetic polymorphism in explaining variability in ecologically relevant traits, (2) the patterns of genetic variation revealed by neutral markers and ecologically relevant traits, and (3) the evolutionary ecological importance of hybridization events in Daphnia. The need for studies on the evolutionary ecology of sexual reproduction and dispersal via ephippial eggs in Daphnia is stressed.