Associations between animal weapons and corresponding aggressive behaviors are among the most characteristic features of species, yet at the same time their co-expression is itself often strongly dependent on context, such as male condition or population ecology. Yet the mechanisms that modulate associations between aggression, morphology, and biological context remain poorly understood. The biogenic amine serotonin has been shown to regulate a wide range of aggressive and morph-specific behaviors in diverse insect species. However, the extent to which serotonin may coordinate the expression of behavior with morphology across biological contexts remains unclear. In this study, we pharmacologically increased serotonin biosynthesis in males of the polyphenic beetle, Onthophagus taurus, and assessed how this manipulation affects both aggressive and non-aggressive behaviors in alternative fighter and sneaker morphs, as well as in males derived from two rapidly diverging populations characterized by disparate levels of competition for mates. We find (i) that enhancing serotonin biosynthesis increases most measures of aggressive behaviors, but influences only a subset of nonaggressive behaviors, (ii) that similar serotonin-mediated behavioral changes manifest in both morphs within populations more often than just a single morph, and (iii) that males derived from the two focal populations have diverged in their behavioral responsiveness to serotonin up-regulation. Collectively, our study suggests that serotonin signaling plays a critical role in the regulation of male behavior and its evolution, including in the context of rapid, short-term population divergence.

中文翻译：

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血清素对角甲虫不同种群的形态特异性行为的影响不同

动物武器和相应的攻击行为之间的关联是物种最典型的特征之一，但同时它们的共同表达本身往往强烈依赖于环境，例如男性状况或种群生态。然而，调节攻击性、形态和生物环境之间关联的机制仍然知之甚少。生物胺血清素已被证明可以调节不同昆虫物种的各种攻击性和形态特异性行为。然而，血清素在多大程度上可以协调行为表达与跨生物环境的形态学。在这项研究中，我们在药理学上增加了多酚甲虫 Onthophagus taurus 雄性的血清素生物合成，并评估了这种操作如何影响另类战斗机和运动鞋变形中的攻击性和非攻击性行为，以及来自两个快速分化的种群的雄性，其特征是对配偶的竞争水平不同。我们发现 (i) 增强血清素生物合成增加了攻击行为的大多数指标，但仅影响非攻击行为的一个子集，(ii) 类似的血清素介导的行为变化在种群内的两种变形中表现得更频繁，而不仅仅是单一变形，以及(iii) 来自两个焦点人群的男性在对血清素上调的行为反应方面存在差异。总的来说，我们的研究表明，血清素信号在调节男性行为及其进化中起着关键作用，包括在快速、