Rare sexual reproduction by females of “obligate parthenogenetic” lineages of Daphnia cf. pulex

Rare sexual reproduction in otherwise asexual lineages is predicted to strongly alleviate long-term costs of asexuality while avoiding most of the cost of sex. Here, we test for rare sexual reproduction in females of obligate parthenogenetic (OP) lineages of Daphnia cf. pulex. We find that a small proportion, ~0.5%, of offspring contain paternal alleles when they are produced in the presence of males from a so-called cyclical parthenogenetic (CP) lineage of the species, thus demonstrating sexual reproduction. Rare sexual reproduction occurred in two independent tests, using females from two different OP lineages, suggesting that it may be a regular feature in OP lineages of the species. Even though it could not be established whether the sexual events involved fertilization of haploid or diploid eggs, these results disclose a reproductive trait entirely new to Daphnia biology, aligning with recent results in other organisms. Indeed, the occurrence of rare or cryptic events of ..., , # Rare sexual reproduction by females of “obligate parthenogenetic” lineages of Daphnia cf. pulex Dataset DOI: [10.5061/dryad.kd51c5bj8](10.5061/dryad.kd51c5bj8) ## Description of the data and file structure * **Table 1** To estimate the number of adult females present at the end of the experiment in each of the two crossing tests, three random samples were taken (with replacement) from each culture once its volume had been reduced to the total volume indicated. For each sample, the sample volume and the number of adult females contained in the sample was quantified. Those three random samples were later used to calculate the average and standard error (s.e.) of the number of adult females per ml of the total volume, as well as extrapolated to estimate the total number of females in each culture. * **Table 2** In order to estimate the numbers of diapause capsules present at the end of the experiment in each of the two crossing tests, three random samples of 1 ml were taken (with ...,