Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan 48109, USA.
Am Nat. 2010 Aug;176(2):123-30. doi: 10.1086/653664.
The challenge hypothesis was proposed as a mechanism for vertebrates to optimize their testosterone titers by upregulating testosterone during periods of aggressive competition. Here we test key predictions of the challenge hypothesis in an independently evolved endocrine system: juvenile hormone (JH) in a social insect. We assess how social conflict influences JH titers in Polistes dominulus wasps. Aggressive conflict was produced by removing the queen from some colonies (experimental) and a low-ranked worker from other colonies (control). Queen removal produced competition among workers to fill the reproductive vacancy. Workers upregulated their JH titers in response to this social conflict; worker JH titers were higher in queenless than in queenright colonies. Furthermore, JH titers were associated with an individual's ability to dominate rivals; the worker that took over as the replacement queen had a substantially higher JH titer than did other workers. Finally, JH titers were positively associated with aggression in queenless colonies, but there was no relationship between JH and aggression in stable, queenright colonies. Overall, these results match key predictions of the challenge hypothesis and parallel much of the work on testosterone in vertebrates. Social modulation of hormone titers is not confined to a particular endocrine system but is likely to be an adaptive feature of endocrine systems across diverse taxa.
挑战假说提出，脊椎动物通过在具有攻击性的竞争期间上调睾酮来优化其睾酮水平。在这里，我们在一个独立进化的内分泌系统中测试了挑战假说的关键预测：社会性昆虫中的保幼激素（JH）。我们评估了社会冲突如何影响 Polistes dominulus 黄蜂中的 JH 水平。通过从一些群体中移除女王（实验组）和其他群体中的低级工人（对照组）来产生攻击性冲突。女王的移除导致工蜂之间为填补生殖空缺而竞争。工蜂会对这种社会冲突做出反应，上调其 JH 水平；无女王的群体中的工蜂 JH 水平高于有女王的群体。此外，JH 水平与个体支配竞争对手的能力有关；接管为替代女王的工蜂的 JH 水平比其他工蜂高得多。最后，JH 水平与无女王群体中的攻击性呈正相关，但在稳定的、有女王的群体中，JH 与攻击性之间没有关系。总的来说，这些结果符合挑战假说的关键预测，与脊椎动物中关于睾酮的大量研究相似。激素水平的社会调节并不局限于特定的内分泌系统，而是可能是跨不同分类群的内分泌系统的一个适应性特征。
