Paternity success depends on male genetic characteristics in the terrestrial isopod Armadillidium vulgare

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Mate choice for compatible partners has been gaining interest during the past years, which implies that what represents a suitable male varies between females and that genetic diversity in offspring should be increased. In this context, mechanisms of mate choice for heterozygous and/or genetically dissimilar partners can be expected. To test for the presence of such mechanisms in the gregarious crustacean Armadillidium vulgare, we performed experimental crosses allowing a female to reproduce with two males. More heterozygous males had a higher paternity success whatever the number of males (only one or both males) participating in reproduction, which could result from better competing abilities or from female preference for such males. When only one male fathered a brood, this male was the most genetically dissimilar to the female, suggesting the existence of a female choice for dissimilarity. Additionally, the more genetically similar both males were to the female, the fewer offspring were produced per brood. Genetic diversity is thus likely to be involved in both pre- and post-copulatory processes, as well as to have an impact on fitness in this terrestrial isopod. This work improves our understanding of the genetic characteristics involved in mating behaviours, and provides insights on the mechanisms at the basis of genetic diversity maintenance. Amongst the many parameters that can be taken into account during mate choice, genetic characteristics must not be neglected, as more and more studies highlight that what is best for one female may not be best for another. Here, we show that both heterozygosity and genetic similarity can influence paternity success in a gregarious terrestrial isopod. This could have strong implications in terms of fitness as a high genetic similarity has a negative impact on offspring number in this species. This work reflects the growing interest for genetic variables, and is positioned at the interface between molecular biology and behavioural ecology.