Abstracts (first author)
Rejection of the clonal erosion hypothesis: a study of hybridizing Daphnia from ten neighboring lakes
Cyclical parthenogenetic water fleas of the genus Daphnia are commonly used as a model system in ecological and evolutionary research. On the one hand, their capability of sexual reproduction favours genetic variation not only within species, but also between species via interspecific hybridization; on the other hand, asexual reproduction may lead to clonal erosion. In the present study, we tracked ten communities of the D. longispina complex (maximum distance about 30 km) from the beginning to the end of one growing season, using 15 microsatellite loci. The clonal richness remained roughly constant throughout the growing season and all four lakes, leading us to reject the clonal erosion hypothesis. Moreover, some identical multilocus genotypes from parental species were shared among otherwise unconnected lakes, and the genetic setup of the communities and populations matched well with the geographical positions among the lakes; but only for parental species and not for the hybrids. This indicates either strong contemporary gene flow or past colonisation events from neighbouring populations. Overall, the genetic distance among populations was lowest for D. galeata, confirming its invasive nature, modest for D. longispina and the highest for hybrids. Thus, hybrids appear to be locally produced, rather than migrating from neighboring lakes.