Albrecht DJ
Department of Biology, University of New Mexico, Albuquerque
Anim Behav. 2000 Jun;59(6):1227-1234. doi: 10.1006/anbe.1999.1420.
Trivers & Willard (1973, Science, 179, 90-92) developed an economic theory of parental investment to explain how the relative profitability of sons and daughters varies under specific ecological conditions. In their maternal condition hypothesis they proposed that in polygynous species, the sex of an offspring should be associated with the amount of parental care likely to be made available to it. In these species, the amount of parental investment directed towards offspring may differentially influence the fitness of male and female offspring because males in better than average condition as adults may enjoy larger fitness gains than a female would if she were in better than average condition, while the reverse may be true when conditions are poor. I tested this hypothesis by determining the sex of specific offspring within house wren broods. Because hatching is asynchronous and fledging is synchronous in this polygynous species, last-hatched young fledge having received less parental care than their broodmates. I predicted that last-hatched offspring would be more likely to be female. I found that these young were indeed more likely to be females, were more likely to have hatched from last-laid eggs and were fledging in poor condition relative to their broodmates. I propose that female house wrens behave in a manner consistent with the predictions of the Trivers & Willard hypothesis by producing female offspring last in the laying sequence of their clutches. Copyright 2000 The Association for the Study of Animal Behaviour.
特里弗斯和威拉德（1973年，《科学》，第179卷，第90 - 92页）提出了一种亲代投资的经济学理论，以解释在特定生态条件下儿子和女儿的相对收益如何变化。在他们的母体状况假说中，他们提出在一夫多妻制物种中，后代的性别应与可能得到的亲代照料数量相关。在这些物种中，投入到后代的亲代投资量可能会对雄性和雌性后代的适应性产生不同影响，因为成年时状况优于平均水平的雄性可能比处于同样状况的雌性获得更大的适应性提升，而在状况较差时情况可能相反。我通过确定家鹪鹩一窝特定后代的性别来检验这一假说。因为在这个一夫多妻制物种中孵化是异步的，而离巢是同步的，最后孵化出的幼鸟离巢时得到的亲代照料比它们的同窝幼鸟少。我预测最后孵化出的后代更有可能是雌性。我发现这些幼鸟确实更有可能是雌性，更有可能是从最后产下的蛋孵化出来的，并且相对于它们的同窝幼鸟，离巢时状况较差。我提出雌性家鹪鹩的行为方式与特里弗斯和威拉德假说的预测一致，即在一窝蛋的产卵顺序中最后产出雌性后代。版权所有2000年动物行为研究协会。
