Data from: Fine-scale kin recognition in the absence of social familiarity in the Siberian jay, a monogamous bird species

Kin recognition is a critical element to kin cooperation, and in vertebrates, it is primarily based on associative learning. Recognition of socially unfamiliar kin occurs rarely, and it is reported only in vertebrate species where promiscuity prevents recognition of first-order relatives. However, it is unknown whether the recognition of socially unfamiliar kin can evolve in monogamous species. Here, we investigate whether genetic relatedness modulates aggression among group members in Siberian jays (Perisoreus infaustus). This bird species is genetically and socially monogamous and lives in groups that are formed through the retention of offspring beyond independence, and the immigration of socially unfamiliar nonbreeders. Observations on feeders showed that genetic relatedness modulated aggression of breeders towards immigrants in a graded manner, in that they chased most intensely the immigrant group members that were genetically the least related. However, cross-fostering experiments showed that breeders were equally tolerant towards their own and cross-fostered young swapped as nestlings. Thus, breeders seem to use different mechanisms to recognize socially unfamiliar individuals and own offspring. As Siberian jays show a high degree of nepotism during foraging and predator encounters, inclusive fitness benefits may play a role for the evolution of fine-scale kin recognition. More generally, our results suggest that fine-graded kin recognition can evolve independently of social familiarity, highlighting the evolutionary importance of kin recognition for social species.亲缘识别（kin recognition）是亲缘合作的核心要素，在脊椎动物中，其主要依赖联想学习。对社会陌生亲属的识别极为罕见，目前仅在因混交交配而无法识别一级亲属的脊椎动物物种中被报道。然而，社会陌生亲缘识别能否在单配制物种种群中演化，目前仍无定论。 本研究以北噪鸦（Siberian jay，*Perisoreus infaustus*）为研究对象，探究遗传相关性是否会调控社群成员间的攻击行为。该鸟类兼具遗传与社会单配制特征，其社群由独立后仍滞留的后代，以及社会陌生的外来非繁殖个体共同构成。 投食器观测结果显示，繁殖个体对外来个体的攻击程度随遗传相关性呈梯度变化：对遗传相关性最低的外来社群成员，其追逐行为最为剧烈。但交叉抚育实验（cross-fostering experiments）表明，繁殖个体对亲生雏鸟与作为雏鸟交换的寄养幼鸟具有同等的容忍度。 由此可见，繁殖个体似乎采用不同的识别机制来区分社会陌生个体与自身后代。鉴于北噪鸦在觅食与天敌应对过程中存在高度的亲缘偏袒行为，广义适合度收益（inclusive fitness benefits）可能在精细尺度亲缘识别的演化中发挥作用。 总体而言，本研究结果表明，精细尺度的亲缘识别可脱离社会熟悉度独立演化，凸显了亲缘识别对社会性物种种群演化的重要意义。