Data from: Mimetic divergence and the speciation continuum in the mimic poison frog Ranitomeya imitator

While divergent ecological adaptation can drive speciation, understanding the factors that facilitate or constrain this process remains a major goal in speciation research. Here, we study two mimetic transition zones in the poison frog Ranitomeya imitator, a species that has undergone a Müllerian mimetic radiation to establish four morphs in Peru. We find that mimetic morphs are strongly phenotypically differentiated, producing geographic clines with varying widths. However, distinct morphs show little neutral genetic divergence, and landscape genetic analyses implicate isolation-by-distance as the primary determinant of among-population genetic differentiation. Mate choice experiments suggest random mating at the transition zones, although certain allopatric populations show a preference for their own morph. We present evidence that this preference may be mediated by color-pattern specifically. These results contrast with an earlier study of a third transition zone, in which a mimetic shift was associated with reproductive isolation. Overall, our results suggest that the three known mimetic transition zones in R. imitator reflect a speciation continuum, which we have characterized at the geographic, phenotypic, behavioral, and genetic level. We discuss possible explanations for variable progress toward speciation, suggesting that multifarious selection on both mimetic color-pattern and body size may be responsible for generating reproductive isolation.

尽管趋异生态适应（divergent ecological adaptation）可推动物种形成（speciation），但解析促进或制约该过程的影响因素，仍是物种形成研究领域的核心目标之一。本研究以秘鲁地区的模仿箭毒蛙（Ranitomeya imitator）为研究对象，该物种曾经历穆氏（Müllerian）拟态辐射演化，衍生出四种形态型（morphs）；我们针对该物种分布区内的两处拟态过渡带开展研究。研究发现，不同拟态形态型的表型分化显著，形成了宽度各异的地理渐变群（geographic clines）。但不同形态型之间的中性遗传分化（neutral genetic divergence）程度极低；景观遗传学（landscape genetics）分析显示，距离隔离（isolation-by-distance）是种群间遗传分化的主要驱动因素。配偶选择（mate choice）实验表明，在过渡带内种群间存在随机交配现象；不过部分异域种群（allopatric populations）对自身所属的形态型存在偏好。本研究提供证据表明，这种偏好可能特异性地由体色图案（color-pattern）所介导。上述结果与此前针对第三处过渡带的研究结论相悖，后者发现拟态转变与生殖隔离（reproductive isolation）存在关联。综合来看，本研究结果表明，模仿箭毒蛙已知的三处拟态过渡带共同构成了一个物种形成连续体（speciation continuum），我们已从地理、表型、行为及遗传多个层面对其进行了系统表征。本研究还讨论了物种形成进程存在差异的潜在成因，提出针对拟态体色图案与体型的多重选择压力（multifarious selection），可能是生殖隔离形成的关键驱动因素。