Sexual selection in parthenogenetic species

Cyclic parthenogenesis, a strategy whereby organisms go through several cycles of clonal reproduction before a sexual event, is a very common form of reproduction. Although often ignored, sexual reproduction plays an important role in the evolution of cyclic parthenogenetic organisms. Daphnia is one such parthenogenetic organism in which sexual reproduction is rare in most populations. We have studied the sexual process in Daphnia natural populations. Our data clearly show that sexual selection is present in this species, although it is mainly parthenogenetic, and that this selection probably manifests itself through a combination of female choice and male competition. (Duneau et al., BioRxiv 2020a)

We further measured the sperm of several species of Daphnia. We found that they have among the smallest sperm cells ever recorded. Based on a recent phylogeny, we showed that larger sperm seems to have evolved twice independently leading eventually in some clades to the loss of the encapsulation allowing for condensed cells in the spermiduct. (Duneau et al., BioRxiv 2020b)

More details to come