Institute of Biological and Environmental Sciences, School of Biological Sciences, Zoology Building, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK.
Proc Biol Sci. 2012 May 7;279(1734):1700-8. doi: 10.1098/rspb.2011.2230. Epub 2011 Nov 23.
One specific hypothesis explaining the evolution of extra-pair reproduction (EPR) by socially monogamous females is that EPR is under indirect selection because extra-pair offspring (EPO) sired by extra-pair males have higher additive genetic value for fitness than the within-pair offspring (WPO) a female would have produced had she solely mated with her socially paired male. This hypothesis has not been explicitly tested by comparing additive genetic value between EPO and the WPO they replaced. We show that the difference in additive genetic breeding value (BV) between EPO and the WPO they replaced is proportional to the genetic covariance between offspring fitness and male net paternity gain through EPR, and estimate this covariance with respect to offspring recruitment in free-living song sparrows (Melospiza melodia). Recruitment and net paternity gain showed non-zero additive genetic variance and heritability, and negative genetic covariance. Opposite to prediction, EPO therefore had lower BV for recruitment than the WPO they replaced. We thereby demonstrate an explicit quantitative genetic approach to testing the hypothesis that EPR allows polyandrous females to increase offspring additive genetic value, and suggest that there may be weak indirect selection against female EPR through reduced additive genetic value for recruitment of EPO versus WPO in song sparrows.
一个解释社交一夫一妻制雌性发生婚外配（EPR）的具体假设是，EPR 受到间接选择，因为与由配对雄性所生育的后代（WPO）相比，由婚外雄性所生育的额外后代（EPO）具有更高的适合度加性遗传值。这个假设尚未通过比较 EPO 和它们所替代的 WPO 之间的加性遗传值来明确测试。我们表明，EPO 和它们所替代的 WPO 之间的加性遗传育种值（BV）差异与后代适应度和雄性通过 EPR 获得的净父权增益之间的遗传协方差成正比，并根据自由生活的歌雀（Melospiza melodia）的后代招募情况来估计这个协方差。招募和净父权增益显示出非零的加性遗传方差和可遗传性，以及负遗传协方差。与预测相反，EPO 的后代招募的 BV 低于它们所替代的 WPO。因此，我们通过明确的数量遗传方法证明了 EPR 允许多配偶雌性增加后代加性遗传值的假设，并表明在歌雀中，通过降低 EPO 相对于 WPO 的后代招募的加性遗传值，可能对雌性 EPR 存在微弱的间接选择。
