Engqvist Leif, Cordes Nils, Reinhold Klaus
Evolutionary Biology, Bielefeld University, Bielefeld, Germany; Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland.
Evolution. 2015 Feb;69(2):395-406. doi: 10.1111/evo.12591. Epub 2015 Jan 20.
In many species, males possess conspicuous characteristics to attract females. These traits often attract predators as well, and males thus may have to balance the conspicuousness of their signals in relation to the prevailing predation risk. Here we develop a theoretical model of optimal signaling and risk-taking behavior for males differing in the attractiveness of their signals. All else being equal, more attractive males should behave more cautiously. Yet this prediction may drastically change if males differ in any additional characteristic, especially if basal mortality rate or signaling costs are higher or if the vulnerability to predators is lower for attractive males. A key insight from our model is that male competition will create a positive feedback so that selection on male risk-taking strategies is acting in opposite directions. If selection acts on one male type to behave more cautiously, this will strengthen selection on males of the other types to take higher risks and vice versa. Our results further demonstrate that the asset-protection principle, which states that individuals with higher future expectations should behave more cautiously, may often be violated. We also offer an alternative to the handicap principle explaining the often found positive association between male ornamentation and viability: attractive males may simply behave more cautiously.
在许多物种中，雄性具有显著特征以吸引雌性。这些特征往往也会吸引捕食者，因此雄性可能不得不根据当前的捕食风险来平衡其信号的显著程度。在此，我们针对信号吸引力不同的雄性，建立了一个最优信号传递与冒险行为的理论模型。在其他条件相同的情况下，更具吸引力的雄性应该表现得更为谨慎。然而，如果雄性在任何其他特征上存在差异，尤其是如果基础死亡率或信号传递成本更高，或者对于有吸引力的雄性而言，其对捕食者的易感性更低，那么这一预测可能会发生巨大变化。我们模型的一个关键见解是，雄性竞争会产生正反馈，使得对雄性冒险策略的选择朝着相反方向起作用。如果选择促使一种雄性类型表现得更为谨慎，这将强化对其他类型雄性采取更高风险行为的选择，反之亦然。我们的结果进一步表明，资产保护原则（即未来期望更高的个体应该表现得更为谨慎）可能常常被违背。我们还为缺陷原则提供了一种替代解释，以说明经常发现的雄性装饰与生存能力之间的正相关关系：有吸引力的雄性可能只是表现得更为谨慎。
