Data from: Predation cost of a sexual signal in the threespine stickleback

Much evidence exists for sexually selected traits reflecting various components of mate quality, but the factors that limit signal expression and ensure honest signaling are less well known. Predation risk has been proposed to be one factor that could constrain the elaboration of visually conspicuous signals and ensure honesty, but little evidence exists because of limitations of earlier used methods. We investigated using a combination of field observations and experimental work if a conspicuous sexual signal of the threespine stickleback Gasterosteus aculeatus, the red nuptial coloration of the male, increases predation risk. We compared the proportion of colorful males in the gut of a predator in the wild, the perch Perca fluviatilis, to that in the population, and found proportionally more red-colored stickleback in the gut. This indicates that the predator selectively preys on colorful males under natural conditions. To differentiate between the effects of color and behavior on susceptibility to predation, we experimentally investigated the attack behavior of the predator towards breeding stickleback males differing in coloration. We found the predator to preferentially attack more colorful males, independent of their behavior. These results indicate that predation risk is a cost of the sexual signal that could limit expression and influence the honesty of the signal as an indicator of mate quality.

已有大量证据表明，性选择性状能够反映配偶质量的多个维度，但限制信号表达并确保信号诚实性的相关机制却鲜为人知。捕食风险曾被提出是可能约束视觉醒目性信号演化、并维持信号诚实性的因素之一，但由于早期研究方法存在局限，相关实证证据十分匮乏。本研究结合野外观察与实验手段，针对三棘刺鱼（Gasterosteus aculeatus）的醒目性性信号——雄性个体的红色婚装色彩——是否会提升其捕食风险展开了探究。我们对比了野生捕食者河鲈（Perca fluviatilis）的消化道内色彩艳丽的刺鱼个体占比，与野外种群中的该占比，结果发现捕食者消化道内红色刺鱼的比例更高。这一结果表明，在自然环境下该捕食者会选择性捕食色彩更艳丽的雄性刺鱼。为区分体色与行为对捕食易感性的影响，我们通过实验探究了该捕食者对体色存在差异的繁殖期雄性刺鱼的攻击行为。研究发现，无论雄性刺鱼的行为模式如何，捕食者均会优先攻击体色更艳丽的个体。上述结果表明，捕食风险是该性信号的生存成本之一，这一成本可能限制信号的表达程度，并影响该信号作为配偶质量指示物的诚实性。