Institute of Ecology, Evolution and Diversity, Goethe University Frankfurt, Frankfurt am Main, Germany.
Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany.
Environ Microbiol. 2024 Oct;26(10):e16703. doi: 10.1111/1462-2920.16703.
Lichens can withstand fluctuating environmental conditions such as hydration-desiccation cycles. Many species distribute across climate zones, suggesting population-level adaptations to conditions such as freezing and drought. Here, we aim to understand how climate affects population genomic patterns in lichenized fungi. We analysed population structure along elevational gradients in closely related Umbilicaria phaea (North American; two gradients) and Umbilicaria pustulata (European; three gradients). All gradients showed clear genomic breaks splitting populations into low-elevation (Mediterranean zone) and high-elevation (cold temperate zone). A total of 3301 SNPs in U. phaea and 138 SNPs in U. pustulata were driven to fixation between the two ends of the gradients. The difference between the species is likely due to differences in recombination rate: the sexually reproducing U. phaea has a higher recombination rate than the primarily asexually reproducing U. pustulata. Cline analysis revealed allele frequency transitions along all gradients at approximately 0°C, coinciding with the transition between the Mediterranean and cold temperate zones, suggesting freezing is a strong driver of population differentiation. Genomic scans further confirmed temperature-related selection targets. Both species showed similar differentiation patterns overall, but different selected alleles indicate convergent adaptation to freezing. Our results enrich our knowledge of fungal genomic functions related to temperature and climate, fungal population genomics, and species responses to environmental heterogeneity.
地衣能够承受水分蒸发循环等波动的环境条件。许多物种分布在气候带中，表明种群水平适应了诸如冻结和干旱等条件。在这里，我们旨在了解气候如何影响地衣真菌的种群基因组模式。我们沿着亲缘关系密切的 Umbilicaria phaea（北美；两个梯度）和 Umbilicaria pustulata（欧洲；三个梯度）的海拔梯度分析了种群结构。所有梯度都显示出明显的基因组断裂，将种群分为低海拔（地中海区）和高海拔（冷温带）。在 U. phaea 中有 3301 个 SNP 和 U. pustulata 中有 138 个 SNP 在梯度的两端被固定下来。物种之间的差异可能是由于重组率的差异造成的：有性繁殖的 U. phaea 的重组率高于主要无性繁殖的 U. pustulata。单倍型分析显示，所有梯度的等位基因频率都在大约 0°C 处发生转变，这与地中海区和冷温带之间的转变相吻合，表明冻结是种群分化的一个强大驱动力。基因组扫描进一步证实了与温度相关的选择靶标。两个物种总体上表现出相似的分化模式，但不同的选择等位基因表明它们对冻结有趋同适应。我们的研究结果丰富了我们对与温度和气候相关的真菌基因组功能、真菌种群基因组学以及物种对环境异质性的反应的认识。
