Data from: Non-adaptive female pursuit of extra-pair copulations can evolve through hitchhiking

Mounting evidence has indicated that engaging in extra-pair copulations (EPCs) might be maladaptive or detrimental to females. It is unclear why such non-adaptive female behavior evolves. In this study, we test two hypotheses about the evolution of female EPC behavior using population genetic models. First, we find that both male preference for allocating extra-effort to seek EPCs and female pursuit behavior without costs can be maintained and remain polymorphic in a population via frequency dependent selection. However, both behaviors cannot evolve when females with pursuit behavior suffer from a decline in male parental care. Second, we present another novel way in which female pursuit behavior can evolve; indirect selection can act on this behavior through a ratchet-like mechanism involving oscillating linkage disequilibria between the target EPC pursuit locus and two other loci determining male mate choice and a female sexual signal. Although the overall positive force of such indirect selection is relatively weak, our results suggest that it may still play a role in promoting the evolution of female EPC behavior when this behavior is non-adaptive (i.e., it is neutral) or only somewhat maladaptive (e.g., males only occasionally lower parental care when their mates pursue EPCs).越来越多的证据表明，进行婚外交配（extra-pair copulations，EPCs）可能对雌性个体存在适应不良或有害的影响。目前尚不明确这种非适应性的雌性行为是如何演化而来的。本研究利用种群遗传模型，对雌性EPC行为演化的两项假说进行了验证。其一，研究发现，当雌性追求EPC的行为无成本时，雄性投入额外精力寻求婚外交配的偏好，与雌性的这类追求行为，均可通过频率依赖选择在种群中得以维持并保持多态性；但当表现出追求行为的雌性会面临雄性双亲抚育水平下降的情况时，这两种行为均无法演化。其二，本研究提出了一种可促使雌性EPC追求行为演化的全新路径：间接选择可通过棘轮样机制作用于该行为，该机制涉及EPC追求目标基因座（locus）与另外两个分别决定雄性配偶选择和雌性性信号的基因座（loci）之间存在周期性波动的连锁不平衡。尽管此类间接选择的整体正向作用相对较弱，但研究结果表明，当雌性的EPC行为属于非适应性（即中性）或仅存在轻度适应不良（例如，仅在配偶追求婚外交配时，雄性才偶尔降低双亲抚育投入）时，该间接选择仍可在推动雌性EPC行为演化的过程中发挥作用。