Data from: Offspring fitness varies with parental extra-pair status in song sparrows, Melospiza melodia

Numerous studies have tested for indirect selection on female extra-pair reproduction (EPR) by quantifying whether extra-pair young (EPY) are fitter than their within-pair young (WPY) maternal half-siblings. In contrast, the hypothesis that offspring of EPY and WPY (rather than the EPY and WPY themselves) differ in fitness has not been tested, even though inter-generational effects of parental extra-pair status on offspring fitness could alter the magnitude and direction of indirect selection on EPR. We tested whether offspring of EPY song sparrows, Melospiza melodia, were more likely to recruit or produce hatched or recruited offspring over their lifetimes than offspring of WPY. Hatchlings with one or two EPY parents were more likely to recruit and produce hatched offspring than hatchlings with two WPY parents. Furthermore, these relationships differed between maternal versus paternal extra-pair status. Hatchlings with EPY fathers were more likely to recruit and produce offspring than hatchlings with WPY fathers. In contrast, hatchlings with EPY mothers were as likely to recruit as hatchlings with WPY mothers and tended to be less likely to produce recruited offspring. Depending on the causal genetic and environmental mechanisms, such conflicting inter-generational relationships between parental extra-pair status and offspring fitness could substantially influence the evolutionary dynamics of EPR.

诸多研究已通过量化婚外配子代（EPY）是否比其母系半同胞婚内配子代（WPY）具有更高适合度，来检验针对雌性婚外配繁殖（EPR）的间接选择作用。与之相对，关于“婚外配子代与婚内配子代（而非EPY与WPY自身）适合度存在差异”的假说尚未得到检验——即便父母的婚外配状态对子代适合度的跨代效应，可能会改变针对EPR的间接选择的强度与方向。本研究针对歌带鹀（Melospiza melodia），检验了其EPY子代在一生当中，是否比WPY子代更有可能成功招募进入繁殖种群，或是繁育出后代并使其成功孵化或招募进入繁殖种群。拥有一位或两位EPY亲本的雏鸟，比拥有两位WPY亲本的雏鸟，更有可能成功招募进入繁殖种群并繁育后代。此外，这种关联在母系与父系婚外配状态之间存在差异：父亲为EPY的雏鸟，比父亲为WPY的雏鸟更有可能成功招募进入繁殖种群并繁育后代；与之相对，母亲为EPY的雏鸟与母亲为WPY的雏鸟成功招募进入繁殖种群的概率相当，但往往更难繁育出成功招募的后代。根据其潜在的遗传与环境作用机制，父母婚外配状态与子代适合度之间的这种矛盾跨代关联，可能会显著影响EPR的进化动态。