Partner’s age, not social environment, predicts extrapair paternity in wild great tits (Parus major)

An individual’s fitness is not only influenced by its own phenotype, but by the phenotypes of interacting conspecifics. This is likely to be particularly true when considering fitness gains and losses caused by extrapair matings, as they depend directly on the social environment. While previous work has explored effects of dyadic interactions, limited understanding exists regarding how group-level characteristics of the social environment affect extrapair paternity (EPP) and cuckoldry. We use a wild population of great tits (Parus major) to examine how, in addition to the phenotypes of focal parents, two neighborhood-level traits – age and personality composition – predict EPP and cuckoldry. We used the well-studied trait “exploration behavior” as a measure of the reactive-proactive personality axis. Because breeding pairs inhabit a continuous “social landscape”, we first established an ecologically relevant definition of a breeding “neighborhood” through genotyping parents and nestling...个体的适合度不仅受自身表型影响，同时也会受到与其发生互动的同种个体表型的影响。在探讨由婚外配（extrapair matings）引发的适合度增减时，这一效应尤为显著，因为这类适合度变化直接取决于社会环境。尽管已有研究对二元互动的影响展开了探索，但学界对社会环境的群体层面特征如何影响婚外父权（extrapair paternity, EPP）与配偶不忠行为（cuckoldry）的认知仍较为有限。本研究以野生大山雀（Parus major）种群为研究对象，旨在考察除焦点亲代（focal parents）自身表型外，两类邻里层面的特征——年龄与性格组成——如何预测婚外父权与配偶不忠行为。我们采用被广泛研究的探索行为（exploration behavior）作为反应性-主动性性格轴（reactive-proactive personality axis）的量化指标。由于繁殖对栖息于连续的“社会景观”之中，我们首先通过对亲代与雏鸟进行基因分型，确立了具备生态学意义的繁殖“邻里”定义……