Condition-dependent female chemical signals and adaptive male mate choice in the sexually cannibalistic spider Argiope bruennichi

信息素是一种化学物质，在一个物种内的个体之间传递信息。特别是在节肢动物中，化学信号是交流的普遍手段，尤其是在性交流中。男性信息素在女性择偶过程中的作用已经得到了很好的研究。然而，同样广泛存在的基于雌性化学线索的雄性配偶选择直到最近才被承认，理解雌性性信号的进化和适应性雄性配偶选择决策的标准是性选择研究的最后一个空白点。一般来说，只有当(1)选择的收益大于成本和(2)雌性的质量不同时，才有利于雄性选择的进化和交配策略的条件调整。球网蜘蛛Argiope bruennichi满足这两个条件。该物种的雄性交配率非常低，因此与低质量的雌性交配严重影响终生的繁殖成功率。此外，雌性的繁殖力差异很大。行为分析表明，雄性根据雌性的交配状态、年龄和体型来调整交配行为，它们最有可能通过化学线索来评估这些行为。因此，作为对蜘蛛的首次研究，我们建议将化学生态学分析和行为分析结合起来，以扩大我们对雌性性信号的条件和状态依赖性变异及其在雄性择偶中的作用的认识。我们假设雌性布鲁尼奇拟南蝽的化学特征包含条件依赖信息，雄性利用雌性化学特征的变化来做出适应性的交配决定。具体而言，本项目将研究(1)基于雌性化学信号变化的雄性配偶选择，(2)不稳定的雌性信号在配偶评估中的作用，以及(3)雌性是否可以调整其信号努力以最大化其适合度回报。

Pheromones are chemical substances that transmit information between individuals within a species. Particularly in arthropods, chemical signals are the prevalent means of communication, especially in sexual communication. Male pheromones in the context of female mate choice are well studied. Yet, the likewise widespread occurrence of male mate choice based on female chemical cues has only recently been acknowledged and understanding the evolution of female sexual signals and the criteria underlying adaptive male mate choice decisions is one of the last blank spots of sexual selection research. Generally, the evolution of male choosiness and the conditional adjustment of mating tactics are favored only if (1) the benefits of choosing exceed the costs and (2) when females vary in quality. Both conditions are met in the orb-web spider Argiope bruennichi. Males of this species have very low mating rates, hence mating with low-quality females critically affects life-time reproductive success. Moreover, females vary considerably in fecundity. Behavioral assays show that males adjust their mating behavior depending on female mating status, age and size, which they most likely assess via chemical cues. Therefore, as the first study to this aim in spiders, we propose to combine chemical-ecological analyses and behavioral assays on A. bruennichi to broaden our knowledge on condition- and state-dependent variation of female sexual signals and their function in male mate choice. We hypothesize that the chemical profiles of female A. bruennichi contain condition-dependent information and that males use variation in the chemical profiles of females to make adaptive mating decisions. Specifically, this project will investigate (1) male mate choice based on variation in female chemical cues, (2) the role of volatile female cues in mate assessment, and (3) whether females can adjust their signaling effort to maximize their fitness returns.