Müllerian mimicry of a quantitative trait despite contrasting levels of genomic divergence and selection

Hybrid zones, where distinct populations meet and interbreed, give insight into how differences between populations are maintained despite gene flow. Studying clines in genetic loci and adaptive traits across hybrid zones is a powerful method for understanding how selection drives differentiation within a single species, but can also be used to compare parallel divergence in different species responding to a common selective pressure. Here, we study parallel divergence of wing colouration in the butterflies Heliconius erato and H. melpomene, which are distantly related Müllerian mimics that show parallel geographic variation in both discrete variation in pigmentation, and quantitative variation in structural colour. Using geographic cline analysis, we show that clines in these traits are positioned in the roughly the same geographic region for both species, which is consistent with direct selection for mimicry. However, the width of the clines varies markedly between species. This diffe...杂交带（hybrid zone）指不同种群相遇并发生杂交的区域，可为解析种群间差异在基因流存在的前提下仍得以维持的机制提供关键研究视角。对杂交带内遗传位点与适应性性状的渐变群（cline）展开研究，是解析单一物种种内选择如何推动种群分化的高效手段，同时也可用于比较不同物种在共同选择压力下产生的平行分化现象。本研究聚焦红带袖蝶（Heliconius erato）与诗神袖蝶（H. melpomene），二者为远缘的缪勒拟态（Müllerian mimicry）类群，均在色素的离散变异与结构色的数量变异上表现出平行的地理分化特征。借助地理渐变群分析，我们发现两类物种的性状渐变群大致分布于同一地理区域，这与拟态相关的直接选择假说相符。然而，两类物种的渐变群宽度却存在显著差异。这一差异……