Extra-pair paternity in the alpine marmot?: are males from Mars and females from Venus?? Vnebratchnoe ottsovstvo ou alpi?skikh sourkov?: samtsy s Marsa, a samki Venery?? [Paternité hors couple chez la marmotte alpine?: les mâles sont-ils de mars et les femelles de Vénus??].

Résumé

Extra-pair paternities (EPP) result from both male-male competition and female mate choice. Indeed, if evidence suggests that females actively seek extra-pair copulations, male-male competition, by restraining available extra-pair males, may constrain female choice. We therefore investigated, in a highly social monogamous mammal, the alpine marmot (Marmota marmota), how EPP depended on availability of potential extra-pair males measured by the number of subordinate males in the family group and on mate choice for genetic benefits measured as male mate heterozygosity and pair mate relatedness. First, our results reveal that EPP increased with the number of subordinate males in the family group. Second, EPP depended on pair mate relatedness, EPP being rare for pairs characterized by intermediate level of relatedness while increasing either for pairs presenting high or low level of relatedness. Finally, while female relatedness to extra-pair male did not differ from female relatedness to within-pair males, extra-pair males were more heterozygous than within-pair males. Thus, male-male competition may restrain female choice through limiting extra-pair male availability. However, once accounted for social confounding factors, search for genetic benefits may be a likely mechanism driving the EPP in monogamous species.