Data from: The price of insurance: costs and benefits of worker production in a facultatively social bee

Kin selection theory is foundational in helping to explain the evolution of sociality; however, the degree to which indirect fitness benefits may underlie helping behavior in species of early stage sociality has received relatively little empirical attention. Facultatively social bees, which demonstrate multiple forms of social organization, provide prime systems in which to empirically test hypotheses regarding the evolutionary origins of sociality. The subsocial small carpenter bee, Ceratina calcarata, may establish a social nest by manipulating brood provisions to rear a worker daughter, which then assists in critical late-season alloparental care. Here, we combine nest demographic and behavioral data with genetic relatedness estimates to calculate the relative inclusive fitness of both subsocial and social reproductive strategies in C. calcarata. Social mothers benefit from improved likelihood of brood survivorship and have higher fitness than subsocial mothers. Worker daughters have low indirect fitness on average, and will not produce their own offspring. Among-sibling relatedness is significantly higher in social nests than subsocial nests, though mothers of either reproductive strategy may mate multiply. Though this study corroborates the ultimate role of indirect fitness and assured fitness returns in the evolution of social traits, it also offers additional support for maternal manipulation as the proximate mechanism underlying evolutionary transitions in early stage insect societies.亲缘选择理论（Kin selection theory）是阐释社会性演化的基础性理论；然而，针对早期社会性类群中帮助行为背后的间接适合度收益的贡献程度，目前相关实证研究仍相对匮乏。兼性社会性蜂类展现出多种社会组织形式，是实证检验社会性演化起源相关假说的理想研究体系。亚社会性小木匠蜂（Ceratina calcarata）可通过调控幼虫食物供给来培育职蜂后代，该职蜂后代会在季末关键阶段协助完成异亲抚育行为。本研究结合巢群种群统计数据、行为数据与遗传亲缘关系估算值，以此计算C. calcarata中亚社会性与社会性繁殖策略的相对广义适合度。社会性繁殖的蜂后可提升子代存活概率，且适合度高于亚社会性繁殖的蜂后。职蜂后代的平均间接适合度较低，且无法自行繁育后代。尽管两种繁殖策略的蜂后均可多次交配，但社会性巢群中的同胞亲缘系数显著高于亚社会性巢群。本研究既证实了间接适合度与确定性适合度收益在社会性性状演化中的核心作用，同时也为“母体调控作为早期昆虫社会性演化过渡的近因机制”提供了额外佐证。