Data from: Ecology drives natural variation in an extreme antipredator trait: a cost-benefits analysis integrating modeling and field data

Autotomy, or the voluntary shedding of body parts, is an extreme antipredator behaviour used by species in more than 100 animal families. Despite the long-standing observation that the propensity for autotomy can vary extensively among populations, how ecology might drive such variation is still poorly understood. We tested the hypothesis that the variation in this extreme behaviour reflects the balance between costs and benefits determined by the local ecological environment. We focused on three ecological factors that can influence the cost–benefit dynamics of autotomy: predation, male–male competition, and food abundance.
Using tail autotomy in lizards as the study system, we first built an individual-based model to show that environments with high predation, high food abundance, and low male–male competition favoured individuals that autotomized more readily. Moreover, predation likely maintained the ability to autotomize, whereas male–male competition and food abundance fine-tuned the propensity for autotomy. We used field data from five side-blotched lizard populations to verify model results, as well as to test the explanatory power of our model. Field data supported simulation results regarding the roles predation, male–male competition and food abundance. Our model also successfully explained the variation in the propensity for tail autotomy among those five lizard populations. Our approach can be easily extended to examine how ecology might drive adaptive variation in autotomy in other taxa, as well as any traits that share similar cost–benefit dynamics.

自割（autotomy），即主动脱落身体部分的行为，是一类极端的反捕食行为，被超过100个动物科的物种所采用。尽管长期以来学界已观察到，自割倾向在不同种群间存在广泛差异，但生态因素如何驱动这种变异仍不甚明晰。我们检验了如下假说：这种极端行为的变异，反映了由当地生态环境所决定的成本与收益间的平衡。我们聚焦于三种可影响自割成本-收益动态的生态因子：捕食压力、雄性间竞争与食物丰度。
本研究以蜥蜴的尾自割为研究系统，首先构建了基于个体的模型（individual-based model），结果显示，高捕食压力、高食物丰度以及低雄性间竞争的环境，更青睐易于发生自割的个体。此外，捕食压力可能维持了物种的自割能力，而雄性间竞争与食物丰度则对自割倾向起到微调作用。
我们利用来自5个侧斑蜥蜴（side-blotched lizard）种群的野外数据，对模型结果进行验证，并检验本模型的解释效力。野外数据支持了关于捕食压力、雄性间竞争与食物丰度作用的模拟结果。我们的模型还成功解释了上述5个蜥蜴种群间尾自割倾向的变异。本研究的方法可便捷拓展，用于探究生态因素如何驱动其他类群自割行为的适应性变异，以及任何具有类似成本-收益动态的性状。