Abstract
In pair-living mammals, genetic monogamy is extremely rare. One possible reason is that in socially monogamous animals, mate choice can be severely constrained, increasing the risk of inbreeding or pairing with an incompatible or low-quality partner. To escape these constraints, individuals might engage in extra-pair copulations. Alternatively, inbreeding can be avoided by dispersal. However, little is known about the interactions between mating system, mate choice, and dispersal in pair-living mammals. Here we genotyped 41 wild individuals from 14 groups of coppery titi monkeys (Plecturocebus cupreus) in Peruvian Amazon using 18 microsatellite loci. Parentage analyses of 18 young revealed no cases of extra-pair paternity, indicating that the study population is mostly genetically monogamous. We did not find evidence for relatedness- or heterozygosity-based mate choice. Despite the lack of evidence for active inbreeding avoidance via mate choice, mating partners were on average not related. We further found that dispersal was not sex-biased, with both sexes dispersing opportunistically over varying distances. Our findings suggest that even opportunistic dispersal, as long as it is not constrained, can generate sufficient genetic diversity to prevent inbreeding. This, in turn, can render active inbreeding avoidance via mate choice and extra-pair copulations less necessary, helping to maintain genetic monogamy.
Highlights
In pair-living mammals, genetic monogamy is extremely rare
extra-pair paternities (EPP) are common in pair-living, or socially monogamous birds and mammals, including humans, while genetic monogamy is a very rare phenomenon[1,3,4]
We found no evidence for heterozygosity-based mate choice, as homozygosity by loci (HL) was not significantly correlated between pair mates (r = -− 0.527, n = 10 pairs, p = 0.118)
Summary
One possible reason is that in socially monogamous animals, mate choice can be severely constrained, increasing the risk of inbreeding or pairing with an incompatible or low-quality partner To escape these constraints, individuals might engage in extra-pair copulations. In pair-living species with biparental care, potential reproductive rates and, levels of intra-sexual competition will be more similar for males and females[2] As a result, both sexes might be expected to gain benefits from engaging in E PC23. As a result of this constrained mate choice, individuals may end up paired to a genetically incompatible, closely related, or low-quality partner To escape these constraints, animals might seek EPC that would allow them to gain indirect benefits while still taking advantage of direct benefits provided by the social p artner[23]. This is often referred to as “social monogamy” Pair-bonded (who is affiliated with whom): a type of social structure where one adult male and one adult female have an affiliative relationship to the exclusion of other adults, as evidenced by behavioral, emotional, and endocrinological characteristics Sexual monogamy (who mates with whom): a type of social mating system where one adult male and one adult female have an exclusive mating relationship during at least one reproductive season Genetic monogamy (who produces offspring with whom): a type of genetic mating system where one adult male and one adult female produce offspring exclusively with each other over a set of multiple births (at least one reproductive season for species that produce more than one infant per litter and over more than one consecutive reproductive seasons for species with singleton births) Biparental care (who provides parental care): a type of care system where a mother and putative father regularly provide offspring care
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