Data from: Behavioral plasticity and the origins of novelty: the evolution of the rattlesnake rattle

Environmentally induced behavior (behavioral plasticity) has long been hypothesized to promote the origins of novel morphological traits, but this idea remains controversial. One context in which this hypothesis can be evaluated is animal communication, where behavior and morphology are often linked. Here, we examined the evolution of one of nature’s most spectacular communication signals: the rattlesnake rattle. We specifically evaluated whether rattlesnake rattling behavior—and, hence, the rattle—originated from a simple behavior: vibrating the tail when threatened. By reconstructing the ancestral state of defensive tail vibration, we show that this behavior is nearly ubiquitous in the Viperidae (the family that includes rattlesnakes) and widespread in the Colubridae (the largest snake family, nearly all of which are nonvenomous), suggesting a shared origin for the behavior between these families. After measuring tail vibration in 56 species of Viperidae and Colubridae, we show that the more closely related a species was to rattlesnakes, the more similar it was to rattlesnakes in duration and rate of tail vibration. Thus, the rattlesnake rattle might have evolved via elaboration of a simple behavior. These data thereby support the long-standing hypothesis that behavioral plasticity often precedes—and possibly instigates—the evolution of morphological novelty.

长期以来，学界提出假说认为环境诱导行为（行为可塑性，behavioral plasticity）可推动全新形态性状的起源，但该观点仍存在争议。可用于验证该假说的研究场景之一为动物通讯（animal communication）领域，该领域中行为与形态往往存在紧密关联。本研究聚焦于自然界极具代表性的通讯信号之一——响尾蛇尾鸣（rattlesnake rattle）的演化历程，专门验证了响尾蛇鸣尾行为（rattlesnake rattling behavior）以及由此衍生的尾鸣结构是否起源于一种简单行为：遭遇威胁时的尾部振动。通过重构防御性尾部振动的祖先状态，本研究发现该行为在蝰科（Viperidae，包含响尾蛇的蛇类类群）中几乎普遍存在，在游蛇科（Colubridae，全球最大的蛇类科，绝大多数种类无毒）中也广泛分布，这表明该行为在这两个类群间拥有共同起源。在对56种蝰科与游蛇科物种的尾部振动特征进行测定后，本研究发现：物种与响尾蛇的亲缘关系越近，其尾部振动的时长与频率就越接近响尾蛇。由此可见，响尾蛇尾鸣结构可能起源于对一种简单行为的精细化演化。本研究数据从而支持了这一长期存在的假说：行为可塑性往往先于形态性状创新出现，甚至可能推动形态性状创新的演化。