Data from: 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 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.