DOI: 10.5061/dryad.kd51c5bj8
title: Data from: Rare sexual reproduction by females of “obligate parthenogenetic” lineages of Daphnia cf. pulex

description: 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 sexual reproduction may be a common feature in lineages
 previously characterized as obligately parthenogenetic, with significant
 implications for the evolution of obligate asexuality, its long-term
 costs, and its genomic consequences, including the evolution of
 polyploidy.
description: # 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 replacement) from each culture
 once all diapause capsules had been re-suspended in the “total volume”
 indicated. The number of diapause capsules contained in each sample was
 quantified. Those samples were used to calculate the average and standard
 error (s.e.) of the number of diapause capsules per ml of the
 re-suspension, and then extrapolated to estimate the total number of
 diapause capsules produced in each culture. * **Table 3** Number of
 diapause capsules opened in each of the two crossing tests and embryos
 used for the genotyping tests. Two places for embryos are available in
 each diapause capsule. Therefore, the number of diapause capsules
 containing two, one, or no embryos was also recorded. Additional diapause
 capsules were opened to obtain the 450 embryos for the genotyping tests in
 the crossing test DIS85xKAP65. Capsules with zero, one, or two embryos
 were assumed to occur at the same rate as in the first batch of 235
 diapause capsules. The division of the number of embryos by the number of
 places gives the fill rate of diapause capsules, a variable that was later
 calculated in our study thanks to those data.