Ecological correlates of extra-group paternity in mammals

Abstract

Extra-group paternity (EGP) can form an important part of the mating system in birds and mammals. However, our present understanding of its extent and ecology comes primarily from birds. Here, we use data from 26 species and phylogenetic comparative methods to explore interspecific variation in EGP in mammals and test prominent ecological hypotheses for this variation. We found extensive EGP (46% of species showed more than 20% EGP), indicating that EGP is likely to play an important role in the mating system and the dynamics of sexual selection in mammals. Variation in EGP was most closely correlated with the length of the mating season. As the length of the mating season increased, EGP declined, suggesting that it is increasingly difficult for males to monopolize their social mates when mating seasons are short and overlap among females in oestrus is likely to be high. EGP was secondarily correlated with the number of females in a breeding group, consistent with the idea that as female clustering increases, males are less able to monopolize individual females. Finally, EGP was not related to social mating system, suggesting that the opportunities for the extra-group fertilizations and the payoffs involved do not consistently vary with social mating system.

Correlates of genetic monogamy in socially monogamous mammals: insights from Azara's owl monkeys

“…Many other factors have also been related to EPP and EGP rates in birds [32]. Among mammals, EGP was positively correlated with the length of the breeding season, but not the social mating system [9]. By contrast, the social organization (solitary þ family-living versus pair-living species), but not the strength of the pair bond, was predictive of EPP rates in allegedly socially monogamous mammals [33].…”

“…Unfortunately, the social organization of animals is often a poor indicator of their genetic mating system [7][8][9][10]. For example, although the vast majority of passerine birds have traditionally been described as pair-living (Lack, 1968, cited in [8]), in 86% of the species some of the young were not sired by the female's pair-mate and nearly 20% of the broods contained at least one extra-pair chick [8].…”

“…Ever since it was understood that natural selection acts 'at the level of the individual genome' [3, p. 215], it became imperative to examine the genetic consequences of mating and the relationships between social systems and mating systems in order to understand their evolution. Since sexual selection on males and females is greatly influenced by the relationship between the number of mating partners and the reproductive success of males and females [4][5][6], it also has become clear that extra-pair paternity (EPP) and extra-group paternity (EGP) [7][8][9][10] are likely to play an important role in the evolution of mating systems, and that the genetic mating system is more relevant than the social mating system to theories pertaining to the evolution of mating systems.…”

Faithful or not: direct and indirect effects of climate on extra-pair paternities in a population of Alpine marmots

“…Finally, good environmental conditions are expected to lead to a longer mating season and thus, to more time to find extra-pair mates [11]. A study conducted in 2000 showed that yellow-bellied marmots emerged from hibernation earlier than they did 23 years before, due to climate change [48].…”

“…Engaging in extra-pair copulation is a widespread alternative mating tactic [10,11] and a comparative analysis has revealed a positive association between the variability and predictability of annual climatic cycles with the prevalence of extra-pair paternity (EPP) among species of socially monogamous birds [9]. Large inter-annual variations in the frequency of EPP have also been observed within populations [12,13], and climatic variability is likely to be at the origin of these variations.…”