Original paper

Vulnerability of sexual and asexual Eucypris virens (Crustacea, Ostracoda) to predation: an experimental approach with dragonfly naiads

Schmit, Olivier; Martens, Koen; Mesquita-Joanes, Francesc

Abstract

Through the animal kingdom, sexual reproduction often increases predation risk. Sexual mates are usually more detectable by predators because of (visual, acoustic or chemical) sexual signalling, increased mobility during mate search, or higher visual detectability and reduced alertness of mating pairs, amongst other behaviours. In previous studies, we found that macroinvertebrate predator taxa were more common in ponds whose Eucypris virens ostracod populations were parthenogenetic than in populations with males present. Here, we investigate if there is a causal relationship between predation and the E. virens reproductive mode. We experimentally tested whether groups of sexual and parthenogenetic E. virens individuals were equally vulnerable to predation by dragonfly naiads. A first experiment with a balanced mixture of sexual and asexual ostracod prey was designed. In a second experiment, they were exposed separately to predation in distinct groups. Our results indicate an intense predation pressure on E. virens, which increased with predator size. No signi ficant differences were found between parthenogens and sexual E. virens when offered mixed to Sympetrum odonate predators, and only a slightly higher vulnerability of asexuals was noted when offered separately. The absence of an adverse effect of sexual behaviour on predation vulnerability suggests that the association between mode of reproduction and predator abundance observed in the field is not due to the differential vulnerability of sexual and asexual E. virens. The faster population growth potential of parthenogens might allow them to persist in ponds where a strong top-down control could limit survival of sexuals. Alternatively, the observed field association may not indicate a causal relationship, rather the independent effects of habitat temporality on predator abundance and on the E. virens reproductive mode.

Keywords

predationbehavioursexparthenogenesisostracodaodonatasympetrum striolatum