Royle Nick J, Hartley Ian R, Parker Geoff A
School of Biological Sciences, IENS, University of Lancaster, Lancaster LA1 4YQ, UK.
Nature. 2002 Apr 18;416(6882):733-6. doi: 10.1038/416733a.
Parental care is often costly; hence, in sexually reproducing species where both male and female parents rear their offspring (biparental care), sexual conflict over parental investment can arise. Such conflict occurs because each care-giver would benefit from withholding parental investment for use with another partner, leading to a reduction in the amount of care given by one parent at the expense of the other. Here we report experiments to explore the prediction from theory that parents rearing offspring alone may provide greater parental investment than when rearing offspring together with a partner. We found that when the number of offspring per parent, and hence the potential workload, were kept constant, offspring received a greater per capita parental investment from single females than from both parents working together, and that males reared by single mothers were more sexually attractive as adults than their biparentally reared siblings. This difference between single- and two-parent families is due to a reduction in care provided by females when they care together with a male, rather than laziness by males or differences in the begging behaviour of chicks, supporting the claim that sexual conflict in biparental care can reduce the quality of offspring raised.
亲代抚育通常成本高昂；因此，在双亲都抚养后代的有性繁殖物种中（双亲抚育），就可能出现亲代投资方面的性冲突。这种冲突之所以会发生，是因为每个抚育者若减少对当前后代的亲代投资，转而用于与其他配偶繁殖，会从中受益，这就导致一方亲代对后代的抚育减少，而另一方要为此付出代价。在此，我们报告了一些实验，旨在探究理论预测结果：单独抚养后代的亲代可能比与配偶共同抚养后代时投入更多的亲代投资。我们发现，当每个亲代的后代数量以及潜在工作量保持恒定时，单亲雌性给予后代的人均亲代投资要高于双亲共同抚养时的情况，而且由单亲母亲抚养长大的雄性成年后比由双亲抚养的同胞更具性吸引力。单亲家庭与双亲家庭之间的这种差异，是由于雌性与雄性共同抚养时提供的抚育减少，而非雄性偷懒或雏鸟乞食行为存在差异，这支持了证据，支持了双亲抚育中的性冲突会降低后代养育质量这一观点。
