Population structure of a microparasite infecting Daphnia: spatio-temporal dynamics

Background: Detailed knowledge of spatial and temporal variation in the genetic population structure of hosts and parasites is required for understanding of hostparasite coevolution. As hot-spots of contemporary coevolution in natural systems are difficult to detect and long-term studies are restricted to few systems additional population genetic data from various hostparasite systems may provide important insights into the topic. This is particularly true for parasites as these players have been under-investigated so far due to the lower availability of suitable molecular markers. Here we traced genetic variation (based on sequence variants in the internal transcribed spacer region ITS) among seven geographically isolated populations of the ichthyosporean Caullerya mesnili a common microparasite of the cladoceran Daphnia (here the D. longispina hybrid complex). At some sites we also studied parasite genetic variation over time. Then we tested for associations between parasite genotypes...