Resource transfers and evolution: helpful offspring and sex allocation.
Resource transfers and evolution: helpful offspring and sex allocation.
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DOI：
10.1016/j.tpb.2012.09.004
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发表时间：
2013-02
影响因子：
1.4
通讯作者：
Orzack, Steven Hecht
中科院分区：
文献类型：
--
作者：
Stubblefield, J. William;Orzack, Steven Hecht
在一些脊椎动物中，后代帮助它们的父母生育更多的后代。通常只有一种性别的个体成为“巢穴的帮手”。我们分析了这种性别偏向的后代帮助如何影响性别比进化。考虑到年龄结构是至关重要的，因为早期生育的性别比例会影响到后期生育能得到多少帮助；以前的作者没有正确地解释这一事实。当每只雌性在所有后代中产生相同的性别比例时（正如之前所有性别偏向帮助的分析所假设的那样），最优投资策略偏向于更乐于助人的性别。当雌性对每一窝的性别比有同时性的控制权，并且某一特定性别的每一个帮助者都能以固定的数量增加可用于后代生产的资源时，最佳策略是在早期的一窝中只生产更有帮助的一窝，而在后期的一窝中只生产不那么有帮助的一窝。当帮助的回报是非线性的，也就是说，每个帮助者根据帮助者的数量增加了可用于繁殖的资源的数量，最优策略是在早期的育雏中（这可能涉及到两性的生产）最大限度地增加资源的积累，然后在后期的育雏中转向只生产不太帮助的性别。无论性别比例是固定的还是年龄相关的，人口性别比例都倾向于更有帮助的性别。当适合度从帮助展示环境斑块中恢复时，雌性被选择在一些斑块上只生雄性，在另一些斑块上只生雌性，种群性别比可能向任何一个方向偏倚。我们根据关于后代帮助的经验信息来讨论我们的结果，我们通过荟萃分析表明，当父母很少或没有性生活时，他们会产生更多有益的性生活，这一说法没有得到支持。
In some vertebrates, offspring help their parents produce additional offspring. Often individuals of only one sex become “helpers at the nest”. We analyze how such sex-biased offspring helping can influence sex ratio evolution. It is essential to account for age-structure because the sex ratios of early broods influence how much help is available for later broods; previous authors have not correctly accounted for this fact. When each female produces the same sex ratio in all broods (as assumed in all previous analyses of sex-biased helping), the optimal investment strategy is biased towards the more-helpful sex. When a female has facultative control over the sex ratio in each brood and each helper of a given sex increases the resource available for offspring production by a fixed amount, the optimal strategy is to produce only the more-helpful sex in early broods and only the less-helpful sex in later broods. When there are nonlinear returns from helping, i.e., each helper increases the amount of resource available for reproduction by an amount dependent upon the number of helpers, the optimal strategy is to maximize resource accrual from helping in early broods (which may involve the production of both sexes) and then switch to the exclusive production of the less-helpful sex in later broods. The population sex ratio is biased towards the more helpful sex regardless of whether the sex ratio is fixed or age-dependent. When fitness returns from helping exhibit environmental patchiness, females are selected to produce only males on some patches and only females on others, and the population sex ratio may be biased in either direction. We discuss our results in light of empirical information on offspring helping, and we show via meta-analysis that there is no support for the claim of that parents produce more of the helpful sex when that sex is rare or absent.
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影响因子：
2.4
作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
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DOI：
10.1098/rspb.2005.3458
发表时间：
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影响因子：
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作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
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