Data from: Wright's shifting balance theory and the diversification of aposematic signals

Despite accumulating evidence for selection within natural systems, the importance of random genetic drift opposing Wright's and Fisher's views of evolution continue to be a subject of controversy. The geographical diversification of aposematic signals appears to be a suitable system to assess the factors involved in the process of adaptation since both theories were independently proposed to explain this phenomenon. In the present study, the effects of drift and selection were assessed from population genetics and predation experiments on poison-dart frogs, Ranitomaya imitator, of Northern Peru. We specifically focus on the transient zone between two distinct aposematic signals. In contrast to regions where high predation maintains a monomorphic aposematic signal, the transient zones are characterized by lowered selection and a high phenotypic diversity. As a result, the diversification of phenotypes may occur via genetic drift without a significant loss of fitness. These new phenotypes may then colonize alternative habitats if successfully recognized and avoided by predators. This study highlights the interplay between drift and selection as determinant processes in the adaptive diversification of aposematic signals. Results are consistent with the expectations of the Wright's shifting balance theory and represent, to our knowledge, the first empirical demonstration of this highly contested theory in a natural system.

尽管学界已积累了大量关于自然系统内选择作用的实证证据，但与赖特（Wright）和费希尔（Fisher）的进化观相悖的随机遗传漂变（genetic drift）的重要性，依然是学界持续争论的议题。警戒色信号（aposematic signals）的地理分化似乎是评估适应过程相关影响因素的理想研究系统，因为这两种理论均被独立提出用以解释该现象。本研究针对秘鲁北部的模仿箭毒蛙（poison-dart frogs）*Ranitomaya imitator*，通过种群遗传学（population genetics）与捕食实验（predation experiments）评估了遗传漂变与选择的作用效应，研究特别聚焦于两种截然不同的警戒色信号之间的过渡地带。与那些受高捕食压力维持单态警戒色信号的区域不同，过渡地带的特征为选择压力减弱与表型（phenotype）多样性显著提升。在此背景下，表型分化可在适合度（fitness）未发生显著损失的情况下，通过遗传漂变得以发生。若这些新表型能够被捕食者成功识别并规避，便可扩散至替代生境。本研究阐明了遗传漂变与选择之间的相互作用，将其视为警戒色信号适应性分化的决定性过程。研究结果与赖特转移平衡理论（Wright's shifting balance theory）的预期相符，据我们所知，这也是首次在自然系统中为这一极具争议的理论提供实证支撑。