¹Laboratory of Aquatic Ecology, Katholieke Universiteit Leuven, Leuven, Belgium

Correspondence: Dr J Vanoverbeke, Laboratory of Aquatic Ecology, Katholieke Universiteit Leuven, Ch. Deberiotstraat 32, Leuven 3000, Belgium. E-mail: joost.vanoverbeke@bio.kuleuven.be

Received 9 February 2006; Revised 19 December 2006; Accepted 16 February 2007; Published online 28 March 2007.

Abstract

In populations of a cyclical parthenogen, the diversity of clonal lineages, derived from sexually produced eggs, declines during the parthenogenetic phase. Even though Daphnia magna populations from small ponds may harbour millions of individuals, we show that observed clonal and allelic diversity in populations from such small water bodies are lower than in populations from larger water bodies. Populations from small water bodies also show significant fluctuations in allele frequencies among years and a stronger among-population genetic differentiation than populations inhabiting larger water bodies. Persistent founder effects can only explain part of these results. Our data link the population genetic structure of cyclical parthenogens to the size of the habitat and suggest that genetic drift is a more prominent feature of populations inhabiting small water bodies than previously thought.