Reed bunting females increase fitness through extra-pair mating with genetically dissimilar males

Abstract

Females of many socially monogamous species accept or even actively seek copulations outside the social pair bond. As females cannot increase the number of offspring with promiscuous behaviour, the question arises why they engage in extra-pair mating. We used microsatellite data to determine paternity, heterozygosity and genetic relatedness in the reed bunting (Emberiza schoeniclus), a species with high levels of extra-pair paternity (EPP). We found that extra-pair young (EPY) were more heterozygous than within-pair young ( WPY ). The high heterozygosity of the EPY resulted from a low genetic similarity between females and their extra-pair mates. EPY were heavier and larger when compared with their maternal half-siblings shortly before they left the nest. Recapture data indicated a higher fledgling survival of EPY compared with WPY. Our data suggest that reed bunting females increase the viability of their offspring and thus fitness through extra-pair mating with genetically dissimilar males.

Female mate choice across spatial scales: influence of lek and male attributes on mating success of blue-crowned manakins

“…While the adaptive value of particular 'good' genes is likely to be strongly environment-dependent (Zhou et al 2008), high heterozygosity is generally beneficial to individuals and has been associated with increased fitness across a wide range of species, including in wild and nonisolated populations (Brown 1997;Coltman & Slate 2003). Females can effectively increase heterozygosity in offspring by choosing mates that are genetically dissimilar (Suter et al 2007) or highly heterozygous themselves (Hoffman et al 2007). While in the first case the 'best mate' should vary among females and consistent mating biases are not expected, in the second case female preferences could lead to mating skew without erosion of genetic diversity in the population, a potential solution for the 'lek paradox' (Kirkpatrick & Ryan 1991).…”

A distinct reed bunting dawn song and its relation to extrapair paternity

“…A male could indicate his heterozygosity through absolute values of song rate or song diversity. However, in our study the successful extrapair males were not more heterozygous than the unsuccessful but potential extrapair males (Suter et al 2007) and song rate and song diversity were not related to a male's heterozygosity (S.M. Suter, unpublished data).…”

“…In the reed bunting population we studied, extrapair fledglings were more heterozygous and survived at a higher rate than within-pair fledglings (Suter et al 2007). The high heterozygosity of the extrapair young (EPY) was based on a low genetic similarity between females and extrapair males (Suter et al 2007). These earlier findings support the genetic compatibility hypothesis and may explain the extrapair mating behaviour of females (Suter et al 2007).…”

“…Extrapair mates are mostly neighbouring males (Suter et al 2007). Females may thus be able to estimate the quality of these males throughout the breeding season.…”

“…The high heterozygosity of the extrapair young (EPY) was based on a low genetic similarity between females and extrapair males (Suter et al 2007). These earlier findings support the genetic compatibility hypothesis and may explain the extrapair mating behaviour of females (Suter et al 2007). Females may estimate the genetic dissimilarity of a male through song characteristics.…”