Jackson Amy C, Carine Mark A, Chapman Mark A
Biological Sciences University of Southampton Southampton UK.
Algae, Fungi and Plants Division The Natural History Museum London UK.
Ecol Evol. 2024 Aug 8;14(8):e70144. doi: 10.1002/ece3.70144. eCollection 2024 Aug.
Oceanic archipelagos provide striking examples of lineages that have radiated over pronounced ecological gradients. Accompanying this diversification, lineages have evolved adaptations allowing survival in extreme environments. Here, we investigate the genomic basis of ecological adaptation in Canary Island (Brassicaceae), an island relative of . The seven endemic species have diversified in situ along an elevational and ecological gradient, from low-elevation scrub to high-elevation sub-alpine desert. We first generated a reference genome for phylogenetic analysis of which placed it as sister to . Ninety-six gene families were found to be specific to and a further 1087 and 1469 gene families have expanded or contracted in size, respectively, along the branch. We then employed genome re-sequencing to sample 14 genomes across the seven species of Canary Island and an outgroup. Phylogenomic analyses were consistent with previous reconstructions of Canary Island in resolving low- and high-elevation clades. Using the branch-site dN/dS method, we detected positive selection for 275 genes on the branch separating the low- and high-elevation species and these positively selected genes (PSGs) were significantly enriched for functions related to reproduction and stress tolerance. Comparing PSGs to those in analyses of adaptation to elevation and/or latitude in other Brassicaceae, we found little evidence of widespread convergence and gene reuse, except for two examples, one of which was a significant overlap between and a species restricted to high latitudes. The study of Canary Island suggests that the transition to high-elevation environments such as that found in the high mountains of the Canary Islands involves selection on genes related to reproduction and stress tolerance but that repeated evolution across different lineages that have evolved into similar habitats is limited, indicating substantially different molecular trajectories to adaptation.
大洋群岛提供了显著的例子，展示了在明显的生态梯度上辐射演化的谱系。伴随着这种多样化，谱系已经进化出适应能力，使其能够在极端环境中生存。在这里，我们研究了加那利群岛岩芥（十字花科）生态适应的基因组基础，它是岩芥属的一个岛屿近缘种。这七个特有物种沿着海拔和生态梯度在原地发生了分化，从低海拔灌丛到高海拔亚高山荒漠。我们首先生成了一个参考基因组用于系统发育分析，结果将其置于岩芥属的姐妹位置。发现有96个基因家族是加那利群岛岩芥特有的，另外分别有1087个和1469个基因家族在加那利群岛岩芥分支上发生了大小扩张或收缩。然后，我们利用基因组重测序对加那利群岛岩芥的七个物种和一个外类群的14个基因组进行了采样。系统发育基因组分析在解析低海拔和高海拔分支方面与之前对加那利群岛岩芥的重建结果一致。使用分支位点dN/dS方法，我们在分隔低海拔和高海拔物种的分支上检测到275个基因受到正选择，这些正选择基因（PSGs）在与繁殖和胁迫耐受性相关的功能上显著富集。将PSGs与其他十字花科植物适应海拔和/或纬度分析中的PSGs进行比较，我们发现除了两个例子外，几乎没有广泛趋同和基因重复利用的证据，其中一个例子是加那利群岛岩芥与一种局限于高纬度的物种之间存在显著重叠。对加那利群岛岩芥的研究表明，向加那利群岛高山等高海拔环境的转变涉及对与繁殖和胁迫耐受性相关基因的选择，但不同谱系进化到相似栖息地的重复进化是有限的，这表明适应的分子轨迹存在很大差异。
