Neutral genetic differentiation in an island model with cyclical parthenogenesis

Abstract

Abstract Unusually high levels of genetic differentiation are often observed between populations of Daphnia (Crustacea: Cladocera) and other cladocerans. Selection and departure from migration–mutation–drift equilibrium have been invoked to explain this fact. However, the null model of neutral genes at equilibrium has not been explicitly stated. Using a simple island model that takes into account the main characteristics of the cyclical parthenogenetic life-cycle, we show that a high level of differentiation can be obtained for neutral genes at equilibrium if the migration rate during the asexual phase is low and the effective size over the season is reduced, or if mating within clones is common. Recurrent population bottlenecks have a large effect on differentiation and the time to reach equilibrium. Such fluctuating clonal dynamics could be brought about by limitations in the number of clones that hatch and establish themselves each season, or by random associations between neutral and selected genes, as previously suggested in the literature.