Data from: Temporal relationship between genetic and warning signal variation in the aposematic wood tiger moth (Parasemia plantaginis)

Many plants and animals advertise unpalatability through warning signals in the form of colour and shape. Variation in warning signals within local populations is not expected because they are subject to directional selection. However, mounting evidence of warning signal variation within local populations suggests that other selective forces may be acting. Moreover, different selective pressures may act on the individual components of a warning signal. At present, we have a limited understanding about how multiple selection processes operate simultaneously on warning signal components, and even less about their temporal and spatial dynamics. Here, we examined temporal variation of several wing warning signal components (colour, UV reflectance, signal size, and pattern) of two co-occurring colour morphs of the aposematic wood tiger moth (Parasemia plantaginis). Sampling was done in four geographic regions over three consecutive years. We also evaluated each morph's temporal genetic structure by analysing mitochondrial sequence data and nuclear microsatellite markers. Our results revealed temporal differences between the morphs for most signal components measured. Moreover, variation occurred differently in the fore- and hindwings. We found no differences in the genetic structure between the morphs within years and regions, suggesting single local populations. However, local genetic structure fluctuated temporally. Negative correlations were found between variation produced by neutrally evolving genetic markers and those of the different signal components, indicating a non-neutral evolution for most warning signal components. Taken together, our results suggest that differential selection on warning signal components and fluctuating population structure can be one explanation for the maintenance of warning signal variation in this aposematic species.

诸多动植物通过色彩与形态构成的警戒信号（warning signal）来宣示自身的不可食用性。局部种群内的警戒信号变异本不应存在，因为这类信号会受到定向选择（directional selection）的作用。然而，越来越多的研究证据表明局部种群中存在警戒信号变异，这提示可能存在其他选择压力（selective pressure）在发挥调控作用。此外，不同的选择压力可能分别作用于警戒信号组分（warning signal component）的各个独立部分。目前，学界对于多种选择过程如何同时作用于警戒信号组分的机制仍认知有限，对其时间动态（temporal dynamics）与空间动态（spatial dynamics）的了解更是匮乏。本研究以两种同域分布的警戒性木虎蛾（Parasemia plantaginis）色型（morph）为研究对象，对其翅部警戒信号的多个组分——色彩、紫外反射率、信号尺寸与图案——的时间变异展开了调查。研究采样覆盖四个地理区域，历时连续三年。本研究同时通过线粒体序列数据（mitochondrial sequence data）与核微卫星标记（nuclear microsatellite markers），分析了两种色型各自的时间尺度遗传结构（genetic structure）。研究结果显示，在所检测的多数信号组分中，两种色型存在时间维度上的显著差异。此外，前翅与后翅的变异模式存在明显差异。在同一年份与同一区域内，两种色型的遗传结构并无显著差异，这表明二者属于同一局部种群。但局部种群的遗传结构随时间发生了动态波动。研究发现，中性进化（neutral evolution）遗传标记所产生的变异与不同警戒信号组分的变异呈负相关，这提示多数警戒信号组分的演化并非中性。综合来看，本研究结果表明，对警戒信号组分的差异化选择以及种群结构的动态波动，或许可以解释该警戒性物种（aposematic species）为何能够维持其警戒信号的变异。