Data from: Continuous variation in an aposematic pattern affects background contrast, but is not associated with differences in microhabitat use

Variation in aposematic signals was once predicted to be rare, yet in recent years it has become increasingly well-documented. Despite increases in the frequency with which polytypism and polymorphism have been suggested to occur, population-wide variance is rarely quantified. We comprehensively sampled a subpopulation of the poison frog Oophaga sylvatica, a species which is polytypic across its distribution and also shows considerable within-population polymorphism. On one hand, color pattern polymorphism could be the result of multifarious selection acting to balance different signaling functions and leading to the evolution of discrete sub-morphs which occupy different fitness peaks. Alternatively, variance could simply be due to relaxed selection, where variation would be predicted to be continuous. We used visual modeling of conspecific and heterospecific observers to quantify the extent of within-population phenotypic variation and assess whether this variation produced distinct signals. We found that, despite considerable color pattern variation, variance could not be partitioned into distinct groups, but rather all viewers would be likely to perceive variation as continuous. Similarly, we found no evidence that frog color pattern contrast was either enhanced or diminished in the frogs' chosen microhabitats compared to alternative patches in which conspecifics were observed. Within population phenotypic variance therefore does not seem to be indicative of strong selection towards multiple signaling strategies, but rather pattern divergence has likely arisen due to weak purifying selection, or neutral processes, on a signal that is highly salient to both conspecifics and predators.

警戒信号（aposematic signals）的变异曾被认为较为罕见，但近年来相关研究报道愈发丰富。尽管多型现象（polytypism）与多态现象（polymorphism）的被提及频率有所提升，但种群水平的表型变异仍鲜有量化研究。我们对箭毒蛙（Oophaga sylvatica）的一个亚种群开展了全面采样——该物种在其分布范围内呈现多型现象，同时种群内部也存在显著的多态现象。一方面，体色图案多态现象可能源于多重选择作用：不同信号功能间的权衡最终演化出占据不同适合度峰的离散亚型；另一方面，变异也可能仅由放松选择导致，此时变异应呈现连续分布。我们通过针对同种个体（conspecific）与异种个体（heterospecific）的视觉建模，量化了种群内表型变异的程度，并评估该变异是否会产生差异化的信号。研究结果显示，尽管体色图案存在显著变异，但该变异无法被划分为明确的类群，所有观测者均大概率将其感知为连续分布的变异。同理，相较于观测到同种个体的其他生境斑块，蛙类所选微生境（microhabitat）中的体色图案对比度既未显著增强，也未出现弱化，我们未发现相关证据。因此，种群内的表型变异似乎并非指向多重信号策略的强烈选择所导致，反而更可能是：在对同种个体与捕食者均具有高度醒目性的信号上，体色图案的分化源于较弱的净化选择（purifying selection）或中性演化过程。