Biological Sciences, University of Southampton, Southampton, SO17 1BJ, United Kingdom.
Algae, Fungi and Plants Division, Department of Life Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, United Kingdom.
Am J Bot. 2023 May;110(5):e16162. doi: 10.1002/ajb2.16162. Epub 2023 Apr 28.
Oceanic islands offer the opportunity to understand evolutionary processes underlying rapid diversification. Along with geographic isolation and ecological shifts, a growing body of genomic evidence has suggested that hybridization can play an important role in island evolution. Here we use genotyping-by-sequencing (GBS) to understand the roles of hybridization, ecology, and geographic isolation in the radiation of Canary Island Descurainia (Brassicaceae).
We carried out GBS for multiple individuals of all Canary Island species and two outgroups. Phylogenetic analyses of the GBS data were performed using both supermatrix and gene tree approaches and hybridization events were examined using D-statistics and Approximate Bayesian Computation. Climatic data were analyzed to examine the relationship between ecology and diversification.
Analysis of the supermatrix data set resulted in a fully resolved phylogeny. Species networks suggest a hybridization event has occurred for D. gilva, with these results being supported by Approximate Bayesian Computation analysis. Strong phylogenetic signals for temperature and precipitation indicate one major ecological shift within Canary Island Descurainia.
Inter-island dispersal played a significant role in the diversification of Descurainia, with evidence of only one major shift in climate preferences. Despite weak reproductive barriers and the occurrence of hybrids, hybridization appears to have played only a limited role in the diversification of the group with a single instance detected. The results highlight the need to use phylogenetic network approaches that can simultaneously accommodate incomplete lineage sorting and gene flow when studying groups prone to hybridization; patterns that might otherwise be obscured in species trees.
海洋岛屿为理解快速多样化背后的进化过程提供了机会。随着地理隔离和生态变化，越来越多的基因组证据表明，杂交可能在岛屿进化中发挥重要作用。在这里，我们使用测序（GBS）来了解杂交、生态和地理隔离在加那利岛 Descurainia（十字花科）辐射中的作用。
我们对所有加那利岛物种和两个外群的多个个体进行了 GBS。使用超级矩阵和基因树方法对 GBS 数据进行了系统发育分析，并使用 D 统计和近似贝叶斯计算检查了杂交事件。分析气候数据以检验生态与多样化之间的关系。
超级矩阵数据集的分析产生了一个完全解析的系统发育。物种网络表明，D. gilva 发生了杂交事件，这些结果得到了近似贝叶斯计算分析的支持。温度和降水的强烈系统发育信号表明，加那利岛 Descurainia 内部发生了一次主要的生态转变。
岛屿间的扩散在 Descurainia 的多样化中发挥了重要作用，尽管气候偏好只有一次重大转变，但证据表明杂交的作用有限。尽管存在较弱的繁殖障碍和杂种的出现，但杂交似乎只在该群体的多样化中发挥了有限的作用，只检测到一个实例。结果强调了在研究容易发生杂交的群体时需要使用能够同时容纳不完全谱系分选和基因流的系统发育网络方法；否则，这些模式可能会在物种树中被掩盖。
