An Evolutionary Analysis of Biparental Care

由于在基因上没有血缘关系，一夫一妻制的伴侣有一些共同的兴趣，也有一些不同的兴趣。在为幼小的幼崽提供昂贵的双亲照顾的情况下，性伙伴关系很可能是合作和自私的复杂组合：每个个体都可以通过让其伴侣提供更大的投资来提高其一生的生殖成功。最近的ESS模型预测，这样的父母应该只会部分弥补配偶的任何不足，但随着自己的未来(其剩余生殖价值)的减少，应该会变得更加慷慨。由于许多因素根据性别对生活史参数的影响是不对称的，ESS方法导致了关于父母分工的新预测。拟议的野外观察和对家雀的实验将探索这些动态。人工增加供养幼鸟所需的父母劳动(通过将小铅鱼体重暂时固定在直管上，稍微缠住其中一只父母)，并记录纳税父母及其配偶的食物递送表现。同时，他们的日常能源消耗将通过双标签水技术进行评估。在其他鸟巢，父母照顾的成本将被人为地降低(通过食物补充)，并将确定对雄性和雌性父母的影响。因为家雀非常久坐不动，并且在一个季节内繁殖，所以应该有可能对增加的父母劳累如何影响未来的成年繁殖表现和当前的幼鸟招募做出强有力的评估。最初支持期的总体目标是：(1)在三个水平(行为、能量消耗和未来繁殖成功方面)检查男性和女性父母照顾的单独成本；(2)衡量父母提供不同水平的父母对整个后代的影响；(3)定制双亲照顾的ESS模型，以考虑在这一特定系统中观察到的男性和女性之间的差异；(4)检验当前ESS模型中关于父母努力和性别差异应如何与其成本相关的几个关键预测；以及(5)评估从一个筑巢周期到下一个筑巢周期的伙伴关系的中断是否取决于每个亲代的相对工作量的中断。

Being unrelated genetically, monogamous mates have some interests in common, others at odds. Where costly biparental care is provided to nidicolous young, the sexual partnership is likely to be a complex mixture of cooperation and selfishness: each individual may enhance its lifetime reproductive success by getting its partner to supply the greater investment. Recent ESS models predict that such a parent should compensate only partially for any shortfall by its mate, yet should become more generous as its own future (its residual reproductive value) diminishes. Because many factors influence life-history parameters asymmetrically according to gender, the ESS approach leads to novel predictions regarding the parental division of labor. The proposed field observations and experiments on house sparrows will explore these dynamics. Parental labor required for provisioning the brood will be artificially increased (by slightly encumbering one parent with small lead fishing weights affixed temporarily to the rectrices) and the food-delivery performances of both the taxed parent and its mate will be recorded. At the same time their daily energy expenditures will be assessed via the doubly-labelled water technique. At other nests, the costs of parental care will be artificially decreased (via food supplementations) and the impact on both male and female parents will be determined. Because house sparrows are remarkably sedentary and breed multiply within a season, it should be possible to make robust assessments of how increased parental exertion affects both future adult reproductive performance and current-brood recruitment. The overall goals of the initial support period are: (1) to examine the separate costs of male and female parental care at three levels (in terms of behavior, energy expenditure, and future reproductive success); (2) to measure the impact of variable levels of parental provisioning on whole broods of offspring; (3) to tailor ESS models of biparental care so as to account for observed differences between males and females in this particular system; (4) to test several key predictions from current ESS models about how parental effort and sex differences in effort should relate to its costs; and (5) to assess whether discontinuation of partnerships from one nesting cycle to the next is contingent on disruptions of the relative workloads of each parent.