Cyclical parthenogens are a valuable system in which to empirically test theoretical predictions as to the genetic consequences of sexual reproduction in natural populations, particularly if the frequency of sexual relative to asexual reproduction can be quantified. In this study we utilized a series of lake populations of the cyclical parthenogen, Daphnia pulicaria, that vary consistently in their investment in sexual reproduction, to address the questions of whether the ecological variation in investment in sex is detectable at the genetic level, and if so, whether the genetic patterns seen are consistent with theoretical predictions. We show that there is variation in the genetic structure of these populations in a manner consistent with their investment in sexual reproduction. Populations engaging in a high frequency of sex were in Hardy-Weinberg and gametic phase equilibrium, and showed little genotypic differentiation across sampled years. In contrast, populations with a lower frequency of sex deviated widely from equilibrium, had reduced multi-locus clonal diversity, and showed significant temporal genotypic deviation.

AllenLynch Population GenotypesList of microsatellite genotypes for ten loci for each of the 17 samples described in the article. (5 populations x 3 years, 1 population x 2 years). All data were generated using an ABI 3730 sequencer. Population abreviations are: CD-Cloverdale, LL-Little Long, BR-Bristol, W-Warner, P-Pine, B-Baker. The population name (eg CD0434) consists of the population abreviation (CD), the year of sampling (04) and the individual identifier (34). Data is stored as an Excel file.