Mutual mate choice: When it pays both sexes to avoid inbreeding

International audienceConventional sex roles imply choosy caring females and non-discriminating competing males.However, growing experimental data as well as theoretical models suggest that malechoosiness is more common than expected, even in non-sex role reversed species. Inparticular, selectivity of a sex is predicted to evolve in association with high mate availability,high variation in mate quality and high reproductive effort. Here we investigate theselectivity of males and females in a non-sex role reversed species, the cockroach Blattellagermanica, with caring females and competing males. We demonstrate that males andfemales base their mate choice on different criteria and at different steps during the matingsequence. Males assess their relatedness with females during antennal contacts and choose tocourt non-sibling females more vigorously. In turn, females base their mate choice on male’scourting vigour. This mutual mate choice provides shared benefits by both partners byultimately leading to close inbreeding avoidance and associated embryonic lethality observedin inbred matings. We experimentally identify that female choosiness can be explained bytheir high investment in reproduction (embryonic parental care), their low potentialreproductive rate and by male high quality variance (relatedness). On the contrary, maleselectivity seems to be a primarily a consequence of female quality variance. Our studyprovides experimental supports to theoretical predictions of evolutionary models andhighlights the need to consider both male and female selectivity, even in non-sex role reversedspecies