MHC-associated mating strategies and the importance of overall genetic diversity in an obligate pair-living primate
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Mate choice is one of the most important evolutionary mechanisms. Females can improve their fitness by selectively mating with certain males. We studied possible genetic benefits in the obligate pair-living fat-tailed dwarf lemur (Cheirogaleus medius) which maintains life-long pair bonds but has an extremely high rate of extra-pair paternity. Possible mechanisms of female mate choice were investigated by analyzing overall genetic variability (neutral microsatellite marker) as well as a marker of adaptive significance (major histocompatibility complex, MHC-DRB exon 2). As in human medical studies, MHC-alleles were grouped to MHC-supertypes based on similarities in their functional important antigen binding sites. The study indicated that females preferred males both as social and as genetic fathers for their offspring having a higher number of MHC-alleles and MHC-supertypes, a lower overlap with female’s MHC-supertypes as well as a higher genome wide heterozygosity than randomly assigned males. Mutual relatedness had no influence on mate choice. Females engaged in extra-pair mating shared a significant higher number of MHC-supertypes with their social partner than faithful females. As no genetic differences between extra-pair young (EPY) and intra-pair young (IPY) were found, females might engage in extra-pair mating to ‘correct’ for genetic incompatibility. Thus, we found evidence that mate choice is predicted in the first place by the ‘good-genes-as-heterozygosity hypothesis’ whereas the occurrence of extra-pair matings supports the ‘dissassortative mating hypothesis’. To the best of our knowledge this study represents the first investigation of the potential roles of MHC-genes and overall genetic diversity in mate choice and extra-pair partner selection in a natural, free-living population of non-human primates.
KeywordsMate choice MHC class II Microsatellites Pair-living lemur Extra-pair partner Cheirogaleus medius Madagascar
We are grateful to the “Commission Tripartite” of the Malagasy Government, the “Laboratoire de Primatologie et des Vertébrés de l´Université d´Antananarivo”, the “Parc Botanique et Zoologique de Tsimbazaza”, the “Ministère pour la Production Animale” and the “Département des Eaux et Forêts” for their collaboration and permission to work in Madagascar. Many thanks to the ‘Centre de Formation Professionnelle Forestière de Morondava’, B. Rakotosamimanana, R. Rasoloarison, and L. Razafimanantsoa for logistical support, and to the German Primate Centre (DPZ) for the opportunity to work at the field station. We thank I. Tomaschweski for technical assistance in the lab, A. Hapke and H. Zischler for introducing microsatellite analyses and J. Ganzhorn for unflagging support. Two anonymous reviewers provided helpful comments on a former version of this manuscript. This study was made possible by the German Science Foundation (So 428/4-1, So 428/4-2).
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