Data from: Simulated hatching failure predicts female plasticity in extra-pair behavior over successive broods

While many studies have investigated the occurrence of extra-pair paternity (EPP) and its adaptive significance in wild population of birds, we still know surprising little about the plasticity in mating behavior of females at the individual level and how it affects the patterns of paternity. To address this question, we focused on the direct fertility benefit hypothesis for the function of EPP and studied if female birds react in extra-pair mating behavior after reproductive failures using a wild population of the Japanese great tit, Parus minor, a socially monogamous passerine with a moderate frequency of EPP and a high multiple brooding rate. We simulated hatching failure by replacing with artificial eggs during the egg laying period to investigate if females subsequently altered their mating behavior and became more promiscuous to improve reproductive success in their following clutches. The proportion of extra-pair offspring per clutches of both experimental and control pairs increased in the second clutches (replacement and repeat), but compared to the control pairs, the increase in the experimental pairs was significantly greater. The present study suggests that individual females appear to be making decisions based on specific cues and flexibly altering mating behavior in adaptive ways. Also, our results are compatible with one of the long-debated hypotheses for the evolutionary maintenance of EPP which predicts females gain direct fitness benefit through increased reproductive success from mating multiply.

尽管已有诸多研究探讨了野生鸟类种群中的婚外父权（extra-pair paternity, EPP）发生情况及其适应性意义，但我们对雌性个体层面交配行为的可塑性及其对父权模式的影响仍知之甚少。为解答这一问题，本研究聚焦于阐释EPP功能的直接生育收益假说，以日本大山雀（Parus minor）这一社会一夫一妻制雀形目鸟类（其EPP发生频率中等且多次育雏率较高）的野生种群为研究对象，探究繁殖失败后雌性是否会调整其婚外交配行为。研究人员在产卵期通过替换人工卵的方式模拟孵化失败，以此考察雌性是否会随后改变交配行为、变得更具混交性，进而提升后续窝卵的繁殖成功率。实验组与对照组繁殖对的每窝婚外子代占比在第二窝卵（替换窝与重复窝）中均有所上升，但相较于对照组，实验组的上升幅度显著更高。本研究表明，雌性个体似乎会依据特定线索做出决策，并以适应性方式灵活调整交配行为。此外，本研究结果与长期以来用于解释EPP进化维持的诸多争议假说之一相符——该假说预测雌性可通过多次交配提升繁殖成功率，从而获得直接适合度收益。