Data from: Proximate causes of variation in dermal armour: insights from armadillo lizards

Although it is widely assumed that body armour in animals evolved to thwart predator attacks, assessing the role that predators may play in shaping defensive morphologies has proven to be difficult. Recent studies suggest that body armour might be influenced by additional factors besides predation, and/or even by sexual selection. We investigated variation in dermal armour in 13 populations of armadillo lizards (Ouroborus cataphractus), spanning the entire distribution range of the species. We obtained thickness measurements of osteoderms – bony plates embedded in dermal layer of the skin – using micro- and nano-computed tomography. Using these data, we examined the effects of predation pressure/risk and climatic variables on dermal armour variation and addressed sexual and ontogenetic influence. Our results show that climate is the only factor affecting variation in dermal armour. Populations inhabiting more arid environments, characterized by low summer precipitation and mild winter temperatures, are relatively more armoured than those present in less arid environments. In contrast to our expectations, predation pressure or perceived predation risk was not associated with osteoderm thickness. The results of our study support the idea that the evolution of defensive traits might not be driven exclusively by predator-prey interactions, but could be moulded by environmental factors. In particular, we highlight the role of dermal armour as a potentially important mechanism to reduce evaporative water loss in arid environments.尽管学界普遍认为动物的躯体装甲（body armour）是为抵御捕食者攻击而演化形成，但评估捕食者在塑造防御形态中所发挥的作用，却始终颇具挑战。近期研究表明，躯体装甲的演化可能并非仅受捕食压力影响，还存在其他驱动因素，甚至可能与性选择相关。我们针对犰狳蜥（armadillo lizards，学名Ouroborus cataphractus）的13个种群展开皮肤装甲（dermal armour）变异研究，覆盖该物种的整个自然分布范围。我们通过显微及纳米计算机断层扫描（micro- and nano-computed tomography）测量了骨板（osteoderms）——嵌入皮肤真皮层的骨质板片——的厚度。基于上述测量数据，我们分析了捕食压力/风险与气候变量对皮肤装甲变异的影响，并探讨了性别与个体发育因素的作用。研究结果显示，气候是唯一影响皮肤装甲变异的因素。相较于干旱程度较低的生境，栖息于夏季降水稀少、冬季气温温和的干旱环境中的种群，其皮肤装甲发育程度相对更高。与我们的预期相悖，捕食压力或感知到的捕食风险与骨板厚度并无关联。本研究结果支持了如下观点：防御性状的演化未必仅由捕食者-猎物相互作用驱动，亦可受环境因素塑造。尤为重要的是，我们强调了皮肤装甲作为干旱环境中减少蒸发失水的潜在关键机制的作用。