Repeated evolution can provide insight into the mechanisms that facilitate adaptation to novel or changing environments. Here we study adaptation to altitude in two tropical butterflies, Heliconius erato and H. melpomene, which have repeatedly and independently adapted to montane habitats on either side of the Andes. We sequenced 518 whole genomes from altitudinal transects and found many regions differentiated between highland (~ 1200 m) and lowland (~ 200 m) populations. We show repeated genetic differentiation across replicate populations within species, including allopatric comparisons. In contrast, there is little molecular parallelism between the two species. By sampling five close relatives, we find that a large proportion of divergent regions identified within species have arisen from standing variation and putative adaptive introgression from high-altitude specialist species. Taken together our study supports a role for both standing genetic variation and gene flow from independently adapted species in promoting parallel local adaptation to the environment.

重复进化可以深入了解促进适应新环境或不断变化的环境的机制。在这里，我们研究了两种热带蝴蝶Heliconius erato和H. melpomene对海拔的适应，它们反复独立地适应了安第斯山脉两侧的山地栖息地。我们对来自海拔横断面的 518 个全基因组进行了测序，发现许多区域在高地 (~ 1200 m) 和低地 (~ 200 m) 种群之间存在差异。我们展示了物种内重复种群的重复遗传分化，包括异域比较。相比之下，这两个物种之间几乎没有分子平行性。通过对五个近亲进行抽样，我们发现在物种内确定的大部分分歧区域是由高海拔专业物种的站立变异和推定的适应性渐渗引起的。