Nesting strategy shapes territorial aggression but not testosterone: A comparative approach in female and male birds
Nesting strategy shapes territorial aggression but not testosterone: A comparative approach in female and male birds
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DOI：
10.1016/j.yhbeh.2021.104995
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发表时间：
2021-05-14
影响因子：
3.5
通讯作者：
Rosvall, Kimberly A.
中科院分区：
文献类型：
--
作者：
Lipshutz, Sara E.;Rosvall, Kimberly A.
尽管竞争在两性中普遍存在，但我们对形成竞争性生殖表型的直接和最终机制的理解主要源于对雄性之间的配偶竞争的研究。我们评估了一种假设，即繁殖所需资源（即巢址）的有限性是驱动雌雄鸟类领土竞争和睾丸激素分泌的关键变量。专性次级巢穴筑巢在鸟类谱系中不断进化，为探索有限巢穴的竞争如何形成物种间的攻击及其潜在机制提供了有用的比较背景。尽管来自一种或另一种洞穴筑巢物种的证据表明，领土侵略对雌性和雄性都是适应性的，但这还没有在比较框架中得到验证。我们预测，与筑巢策略限制较少的近亲相比，洞穴筑巢会产生更强大的领土侵略。我们的焦点物种是同一鸟类科的两个专性次级巢巢物种和两个具有更灵活筑巢策略的亲缘物种：树燕（Tachycineta bicolor）和仓燕（Hirundo rustica）；东部蓝鸟（Sialia sialis）与美洲知更鸟（Turdus migratorius）。我们利用模拟领土入侵的方法分析了同种攻击行为，发现腔巢物种比其近亲表现出更大的领土攻击行为。这种模式对女性和男性都适用。由于领土侵略通常与睾酮水平升高有关，我们也假设洞巢物种在循环中表现出更高的睾酮水平。然而，尽管有相关证据表明雌性树燕的睾丸激素与更高的身体攻击率有关，但腔巢物种的雄性和雌性循环中的睾丸激素都不高。我们关注的是与两性相关的背景——对重要繁殖资源的竞争——为共同考虑女性和男性生殖竞争的直接和最终驱动因素提供了一个有用的框架。
Our understanding of the proximate and ultimate mechanisms shaping competitive reproductive phenotypes primarily stems from research on male-male competition for mates, even though competition is widespread in both sexes. We evaluate the hypothesis that the restricted nature of a resource required for reproduction, i.e. nest site, is a key variable driving territorial competition and testosterone secretion in female and male birds. Obligate secondary cavity-nesting has evolved repeatedly across avian lineages, providing a useful comparative context to explore how competition over limited nest cavities shapes aggression and its underlying mechanisms across species. Although evidence from one or another cavity-nesting species suggests that territorial aggression is adaptive in both females and males, this has not yet been tested in a comparative framework. We predicted that cavity-nesting generates more robust territorial aggression, in comparison to close relatives with less restrictive nesting strategies. Our focal species were two obligate secondary cavity-nesting species and two related species with more flexible nesting strategies in the same avian family: tree swallow (Tachycineta bicolor) vs. barn swallow (Hirundo rustica); Eastern bluebird (Sialia sialis) vs. American robin (Turdus migratorius). We assayed conspecific aggression using simulated territorial intrusion and found that cavity-nesting species displayed greater territorial aggression than their close relatives. This pattern held for both females and males. Because territorial aggression is often associated with elevated testosterone, we also hypothesized that cavity-nesting species would exhibit higher testosterone levels in circulation. However, cavity-nesting species did not have higher testosterone in circulation for either sex, despite some correlative evidence that testosterone is associated with higher rates of physical attack in female tree swallows. Our focus on a context that is relevant to both sexes - competition over essential breeding resources - provides a useful framework for co-consideration of proximate and ultimate drivers of reproductive competition in females and males.