Data from: Kin effects on energy allocation in group-living ground squirrels

The social environment has potent effects on individual phenotype and fitness in group-living species. We asked whether the presence of kin might act on energy allocation, a central aspect of life-history variation. Using a 22-year data set on reproductive and somatic allocations in Columbian ground squirrels (Urocitellus columbianus), we tested the effects of co-breeding and non-breeding kin on the fitness and energy allocation balance between reproduction and personal body condition of individual females. Greater numbers of co-breeding kin had a positive effect on the number of offspring weaned, through the mechanism of altering energy allocation patterns. On average, females with higher numbers of co-breeding kin did not increase energy income but biased energy allocation towards reproduction. Co-breeding female kin ground squirrels maintain close nest burrows, likely providing a social buffer against territorial invasions from non-kin ground squirrels. Lower aggressiveness, lower risks of infanticide from female kin and greater protection of territorial boundaries may allow individual females to derive net fitness benefits via their energy allocation strategies. We demonstrated the importance of kin effects on a fundamental life-history trade-off.

群居物种的社会环境对个体表型（phenotype）与适合度（fitness）具有显著影响。本研究旨在探究亲属的存在是否会作用于能量分配（energy allocation）——这是生活史变异（life-history variation）的核心维度。我们基于哥伦比亚黄鼠（Urocitellus columbianus）长达22年的繁殖分配与躯体分配数据集，检验了共繁殖亲属与非繁殖亲属对雌性个体适合度，以及繁殖与自身身体状态间能量分配平衡的影响。共繁殖亲属的数量越多，通过改变能量分配模式的机制，对断奶幼崽数量产生正向影响。平均而言，拥有更多共繁殖亲属的雌性个体并未提升能量摄入，而是将能量分配倾向于繁殖活动。共繁殖的雌性黄鼠亲属会维持邻近的巢洞，这可能为其提供抵御非亲属黄鼠领地入侵的社会缓冲。更低的攻击性、来自雌性亲属的杀婴（infanticide）风险降低，以及对领地边界更有效的保护，使得雌性个体能够通过自身的能量分配策略获得净适合度收益。本研究证实了亲属效应对于核心生活史权衡（life-history trade-off）的重要性。