Analysis of within-individual variation in extrapair paternity in blue tits (Cyanistes caeruleus) shows low repeatability and little effect of changes in neighborhood

Abstract

Many studies investigated variation in the frequency of extrapair paternity (EPP) among individuals. However, our understanding of within-individual variation in EPP remains limited. Here, we comprehensively investigate variation in EPP at the within-individual level in a population of blue tits (Cyanistes caeruleus). Our study is based on parentage data comprising >10 000 genotyped offspring across 11 breeding seasons. First, we examined the repeatability of the occurrence of EPP, the number of extrapair offspring, the number of extrapair partners, and the occurrence of paternity loss using data from males and females that bred in multiple years. Second, we tested whether within-individual changes in EPP between breeding seasons relate to between-year changes in the local social environment. Repeatabilities were generally low but significant for the occurrence and number of extrapair young in females and for whether a male sired extrapair young or not. We found no evidence that the presence of the former social partner or changes in the proportion of familiar individuals or in phenotypic traits of the neighbors influenced changes in levels of EPP in females. However, in adult males, a decrease in the average body size of male neighbors was associated with higher extrapair siring success. If confirmed, this result suggests that the competitive ability of a male relative to its neighbors influences his extrapair mating success. We suggest that alternative hypotheses, including the idea that within-individual changes in EPP are due to “chance events” rather than changes in an individual’s social breeding environment, deserve more consideration.

Winter associations predict social and extra-pair mating patterns in a wild songbird

“…A previous study found no evidence that the proportion of familiar neighbours (i.e. familiar from [26]. Here we examined the associations among individuals that arose during the preceding non-breeding season.…”

“…For instance, a social surrounding including many opposite-sex members might favour extra-pair behaviour, and the frequency of social associations could be informative about who will mate with whom [23]. However, the effects of the social environment on patterns of EPP have rarely been investigated, despite potentially being able to give valuable insights into the expression of extra-pair behaviour [23,26].…”

“…Research on EPP has predominately focused on events or circumstances during the breeding season. For instance, several studies investigated the link between EPP and (a) local breeding density, reflecting the potential number of social associates [20,21,27], (b) the phenotypic composition of the breeding environment [26,28] or (c) associations of opposite-sex individuals during the female's fertile period (e.g. at nest-boxes [29]).…”

Opposite-sex associations are linked with annual fitness, but sociality is stable over lifetime

“…Sociality functions as an emergent trait of behavioural preference and personality (Aplin et al 2014;Plaza et al 2020). Thus, some individuals are consistently more inclined to socialise than others, as is demonstrated in mammals (Silk et al 2009;Proops et al 2021;Strickland et al 2021) and birds (Croft et al 2009;Aplin et al 2015;Thys et al 2017;Plaza et al 2020;Beck, Valcu, and Kempenaers 2020), but not exclusively (Krause et al 2000;Dimitriadou, Croft & Darden 2019). Sociality is mediated by the social environment, i.e.…”

Local male breeding density affects extra‐pair paternity in a south temperate population of grass wrensCistothorus platensis

“…Demographic variables are thought to play a central role in shaping genetic mating systems, as the frequency of EPP is expected to be constrained by the distribution and availability of potential mates in both space and time (Westneat and Sherman 1997, Griffith et al 2002, Shuster and Wade 2003). However, there is still no consensus on the general role of demographic variation in driving variation in EPP among individuals and across species (Brouwer and Griffith 2019, Beck et al 2020).…”