Data from: From forest to city: Urbanization modulates relative abundance of anti-predator coloration

Increased urbanization has resulted in community changes including alteration of predator communities. Little is known, however, about how such changes affect morphological anti-predator traits. Given the importance of coloration in predator avoidance, this trait in particular is expected to be susceptible to novel selective environments in urban areas. Here we investigate the coloration pattern of a Neotropical anuran species, the túngara frog (Engystomops pustulosus), along an urbanization gradient. Túngara frogs have two distinct color patterns (unstriped and striped) which we found to occur at different frequencies along an urbanization gradient. Striped individuals increased in frequency with urbanization. To assess the strength of selection imposed by predators on the two color morphs, we deployed clay models of túngara frogs in forest and semi-urban populations. In addition, we examined microhabitat selection by individuals of the different morphs. We found higher predation rates associated with urbanization than forested areas. In particular, frogs from forested habitats had lower number of attacks by avian predators. Contrary to our predictions, however, predation rates were similar for both color morphs independent of urbanization. Also, coloration of the frogs did not affect their microhabitat preference. Overall, túngara frogs are more likely to have a striped coloration pattern in semi-urban areas where predation by birds is higher than in the forest. Our findings suggest that factors other than predation pressure shape the coloration pattern of urban frogs and emphasize the complex nature of effects that anthropogenic changes in habitat and predator communities may have on prey morphology.

城市化进程的加剧引发了群落结构改变，其中包括捕食者群落的变化。然而，目前学界对这类变化如何影响猎物的形态学反捕食性状仍知之甚少。鉴于体色在反捕食防御中的重要作用，该性状预计极易受到城市地区新型选择环境的影响。
本研究沿城市化梯度，对新热带区无尾两栖类物种——泡蟾（túngara frog, Engystomops pustulosus）的体色模式展开调查。泡蟾存在两种截然不同的体色模式：无纹型与条纹型。我们发现，二者在城市化梯度上的出现频率存在显著差异，随着城市化水平提升，条纹型个体的出现频率逐渐升高。
为评估捕食者对两种体色形态型的选择强度，我们在森林种群与半城市种群中放置了泡蟾的黏土模型。此外，我们还调查了不同体色形态型个体的微生境选择偏好。
研究结果显示，相较于森林区域，城市化区域的捕食率更高；具体而言，栖息于森林生境的泡蟾遭遇鸟类捕食者攻击的次数更少。但与我们的预测相悖的是，无论城市化水平如何，两种体色形态型的捕食率均无显著差异。同时，泡蟾的体色也不会影响其微生境选择偏好。
总体而言，相较于森林区域，在鸟类捕食压力更高的半城市地区，泡蟾更倾向于呈现条纹体色模式。本研究结果表明，除捕食压力外，其他因素共同塑造了城市蛙类的体色模式；同时也凸显了人类活动引发的生境与捕食者群落变化，对猎物形态产生影响的复杂本质。