Data from: Adaptive differentiation coincides with local bioclimatic conditions along an elevational cline in populations of a lichen-forming fungus

Background: Many fungal species occur across a variety of habitats. Particularly lichens, fungi forming symbioses with photosynthetic partners, have evolved remarkable tolerances for environmental extremes. Despite their ecological importance and ubiquity, little is known about the genetic basis of adaption in lichen populations. Here we studied patterns of genome-wide differentiation in the lichen-forming fungus Lasallia pustulata along an altitudinal gradient in the Mediterranean region. We resequenced six populations as pools and identified highly differentiated genomic regions. We then detected gene-environment correlations while controlling for shared population history and pooled sequencing bias, and performed ecophysiological experiments to assess fitness differences of individuals from different environments. Results: We detected two strongly differentiated genetic clusters linked to Mediterranean and temperate-oceanic climate, and an admixture zone, which coincided with the transition between the two bioclimates. High altitude individuals showed ecophysiological adaptations to wetter and more shaded conditions. Highly differentiated genome regions contained a number of genes associated with stress response, local environmental adaptation, and sexual reproduction. Conclusions: Taken together our results provide evidence for a complex interplay between demographic history and spatially varying selection acting on a number of key biological processes, suggesting a scenario of ecological speciation.

研究背景：诸多真菌物种广泛分布于多样生境之中。其中与光合共生伙伴形成共生关系的地衣 (lichen)，演化出了对极端环境的卓越耐受能力。尽管地衣生态意义重大且分布广泛，但学界对地衣种群适应的遗传基础仍知之甚少。本研究以地中海区域沿海拔梯度分布的地衣型真菌Lasallia pustulata为对象，分析其全基因组分化模式。我们对6个种群开展混合重测序，鉴定出高度分化的基因组区域。随后在控制共同种群历史与混合测序偏差的前提下，检测基因-环境关联，并实施生理生态学实验以评估不同环境来源个体的适合度差异。研究结果：我们检测到两个与地中海气候、温带海洋性气候相关的高度分化遗传簇，以及一处混合区，该混合区与两种生物气候的过渡带相吻合。高海拔个体展现出对更湿润、更荫蔽环境的生理生态适应。高度分化的基因组区域包含多个与胁迫响应、本地环境适应以及有性生殖相关的基因。研究结论：综合本研究结果，证实了种群历史与作用于多个关键生物过程的空间异质性选择之间存在复杂相互作用，表明生态物种形成的演化场景。