Parker G A, Schwagmeyer P L
Population and Evolutionary Biology Research Group, University of Liverpool, Liverpool L69 7ZB, United Kingdom.
Am Nat. 2005 Jan;165(1):95-106. doi: 10.1086/426604. Epub 2004 Nov 16.
Trivers proposed that, if parental care by both sexes is advantageous, males should practice a "mixed" strategy of seeking extrapair copulations, while restricting their parental investment to offspring of social mates. We explore circumstances under which males should limit their parental care in the predicted manner. We find that Trivers's "mixed" strategy will generally be evolutionarily stable so long as either socially monogamous or polygynous males usually sire more offspring per brood from a social mate than they typically sire in broods of extrapair mates. Polygynous males should spread investment across their home nests unless the expected number of chicks sired in them differs widely. Whether polygynous males should restrict paternal care to social mates' offspring hinges additionally on resident male investment in broods containing extrapair young: if resident males contribute minimally, some investment by a polygynous extrapair male becomes more advantageous. Recently reviewed data on extrapair fertilization distributions within monogamous and polygynous passerines suggest that extrapair offspring often predominate numerically within their broods, consistent with sperm expenditure theory. Nevertheless, most species conform to the model's criterion regarding relative parentage levels in broods of social versus extrapair mates. Patterns of extrapair parentage thus appear sufficient to stabilize biparental care systems.
特里弗斯提出，如果双亲抚育具有优势，那么雄性应该采取一种“混合”策略，即寻求婚外交配，同时将亲代投资限制在社会配偶的后代身上。我们探讨了在哪些情况下雄性应该以预测的方式限制其亲代抚育行为。我们发现，只要一夫一妻制或多配偶制的雄性通常从社会配偶那里获得的每窝后代数量多于它们在婚外配偶的窝中通常获得的后代数量，特里弗斯的“混合”策略在进化上通常就是稳定的。多配偶制的雄性应该将投资分散到它们的巢穴中，除非它们在这些巢穴中预期能育出的雏鸟数量差异很大。多配偶制的雄性是否应该将父性抚育限制在社会配偶的后代身上，还取决于留巢雄性对含有婚外幼雏的窝的投资：如果留巢雄性贡献极少，那么多配偶制的婚外雄性进行一些投资就会更有利。最近对一夫一妻制和多配偶制雀形目鸟类婚外受精分布情况的综述数据表明，婚外后代在数量上往往在它们的窝中占主导地位，这与精子消耗理论一致。然而，大多数物种符合该模型关于社会配偶与婚外配偶窝中相对亲子关系水平的标准。因此，婚外亲子关系模式似乎足以稳定双亲抚育系统。
