Abstract

Many species possess warning colourations that signal unprofitability to predators. Warning colourations are also thought to provide prey with a ‘predator-free space’ and promote niche expansion. However, how such strategies release a species from environmental constraints and facilitate niche expansion is not clearly understood. Fossoriality in reptiles imposes several morphological limits on head and body size to facilitate burrowing underground, but many fossorial snakes live close to the surface and occasionally move above ground, exposing them to predators. In such cases, evolving antipredator defences that reduce predation on the surface could potentially relax the morphological constraints associated with fossoriality and promote morphological diversification. Fossorial uropeltid snakes possess varying degrees of conspicuous warning colourations that reduce avian predation when active above ground. We predicted that species with more conspicuous colourations will exhibit more robust body forms and show faster rates of morphological evolution because constraints imposed by fossoriality are relaxed. Using a comparative phylogenetic approach on the genus Uropeltis, we show that more conspicuous species tend to have more robust morphologies and have faster rates of head-shape evolution. Overall, we find that the evolution of warning colourations in Uropeltis can facilitate niche expansion by influencing rates of morphological diversification.

中文翻译：

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警告信号促进尾骨节蛇的形态多样化（鳞状：Uropeltidae）

摘要

许多物种具有警告色，向捕食者发出无利可图的信号。警告色还被认为为猎物提供了“无捕食者的空间”并促进了利基市场的扩张。但是，这种策略如何从环境限制中释放物种并促进生态位扩展尚不清楚。爬行动物的骨骼化对头部和身体的大小施加了一些形态学上的限制，以利于在地下挖洞，但是许多骨骼化石蛇生活在地表附近，偶尔会移动到地面上，使它们暴露于食肉动物。在这种情况下，不断发展的减少表面捕食行为的反捕食者防御措施可能会放松与地貌相关的形态学约束，并促进形态多样化。尾骨节骨蛇具有不同程度的明显警告色，当它们在地面上活跃时，它们可以减少禽类的捕食。我们预测，具有显着色泽的物种将表现出更强健的身体形态，并表现出更快的形态演化速率，因为由窝基性施加的约束得以放松。在属上使用比较系统发育方法Uropeltis，我们表明，更明显的物种倾向于具有更强壮的形态，并且具有更快的头部形状演化速率。总体而言，我们发现Uropeltis中警告色的演变可以通过影响形态多样化的速率来促进利基扩展。