Asymmetric larval competition in the parasitoid wasp Nasonia vitripennis: a role in sex allocation?
Asymmetric larval competition in the parasitoid wasp Nasonia vitripennis: a role in sex allocation?
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寄生蜂 Nasonia vitripennis 中的不对称幼虫竞争：在性别分配中的作用？
DOI：
10.1007/s00265-007-0407-1
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发表时间：
2007
影响因子：
2.3
通讯作者：
Sykes E
中科院分区：
文献类型：
--
作者：
Sykes E
性别分配理论为测试动物如何根据环境条件调整自己的行为提供了极好的机会。一个主要的焦点是本地配偶竞争（LMC）的例子，在这种情况下，雌性偏向的后代会产生，以最大限度地增加儿子的交配机会。然而，LMC理论的预测可能会被改变，如果在发展过程中存在对资源的局部竞争和两性竞争能力之间的不对称，就像在从黄蜂到鸟类的动物中看到的那样。在本文中，我们测试了不对称幼虫竞争在多大程度上改变了寄生蜂蜂的LMC理论预测。我们发现两性的体型与寄主内发育的后代数量呈负相关。此外，我们发现，当面临高水平的竞争时，雌性的体型受到竞争后代性别比例的影响，而雄性则不受影响；雌性比例越高，雌性越小。与标准LMC理论所预测的相比，这种不对称竞争应该有利于不那么偏向性的性别比例。然后，我们开发了一个理论模型，可以用我们的数据参数化，使我们能够确定观察到的不对称幼虫性别分配竞争水平的定量后果。我们发现，尽管不对称竞争选择了偏少的性别比例，但与LMC相比，这种影响可以忽略不计。此外，当我们重新分析另一种寄生性物种的现有数据时，发现了不对称的幼虫竞争，得出了类似的结论；Bracon hebetor。因此，我们怀疑不对称的幼虫竞争对性别比进化的影响最大的是那些幼仔数量较少、本地配偶竞争不存在问题的物种，比如鸟类和哺乳动物。
Sex allocation theory offers excellent opportunities for testing how animals adjust their behaviour in response to environmental conditions. A major focus has been on instances of local mate competition (LMC), where female-biased broods are produced to maximise mating opportunities for sons. However, the predictions of LMC theory can be altered if there is both local competition for resources during development and an asymmetry between the competitive abilities of the sexes, as has been seen in animals ranging from wasps to birds. In this paper, we test the extent to which asymmetric larval competition alters the predictions of LMC theory in the parasitoid waspNasonia vitripennis. We found that the body size of both sexes was negatively correlated with the number of offspring developing within the host. Further, we found that when faced with high levels of competition, the body size of females, but not males, was influenced by the sex ratio of the competing offspring; females were smaller when a higher proportion of the brood was female. This asymmetric competition should favour less biased sex ratios than are predicted by standard LMC theory. We then develop a theoretical model that can be parameterised with our data, allowing us to determine the quantitative consequences of the observed level of asymmetric larval competition for sex allocation. We found that although asymmetric competition selects for less biased sex ratios, this effect is negligible compared to LMC. Furthermore, a similar conclusion is reached when we re-analyse existing data from another parasitoid species where asymmetric larval competition has been observed;Bracon hebetor. Consequently, we suspect that asymmetric larval competition will have its greatest influence on sex ratio evolution in species that have smaller clutches and where local mate competition is not an issue, such as birds and mammals.
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