Data from: Spatial and ecological population genetic structures within two island-endemic Aeonium species of different niche width

The Crassulacean genus Aeonium is a well-known example for plant species radiation on oceanic archipelagos. However, while allopatric speciation among islands is documented for this genus, the role of intra-island speciation due to population divergence by topographical isolation or ecological heterogeneity has not yet been addressed. The aim of this study was to investigate intraspecific genetic structures and to identify spatial and ecological drivers of genetic population differentiation on the island scale. We analyzed inter simple sequence repeat variation within two island-endemic Aeonium species of La Palma: one widespread generalist that covers a large variety of different habitat types (Ae. davidbramwellii) and one narrow ecological specialist (Ae. nobile), in order to assess evolutionary potentials on this island. Gene pool differentiation and genetic diversity patterns were associated with major landscape structures in both species, with phylogeographic implications. However, overall levels of genetic differentiation were low. For the generalist species, outlier loci detection and loci–environment correlation approaches indicated moderate signatures of divergent selection pressures linked to temperature and precipitation variables, while the specialist species missed such patterns. Our data point to incipient differentiation among populations, emphasizing that ecological heterogeneity and topographical structuring within the small scales of an island can foster evolutionary processes. Very likely, such processes have contributed to the radiation of Aeonium on the Canary Islands. There is also support for different evolutionary mechanisms between generalist and specialist species.

景天科（Crassulaceae）莲花掌属（Aeonium）是海洋群岛植物物种辐射演化的经典范例。尽管该属的岛屿间异域成种现象已有文献记载，但由地形隔离或生态异质性引发种群分化、进而推动岛内成种的作用机制，迄今尚未得到深入探讨。本研究旨在探究该类群的种内遗传结构，并解析岛屿尺度下遗传种群分化的空间与生态驱动因子。我们针对拉帕尔马岛（La Palma）的两种岛屿特有莲花掌属物种开展了简单序列重复区间（inter simple sequence repeat，ISSR）变异分析：其中一类为广布广适种，可占据多种不同生境类型（大卫氏莲花掌 Ae. davidbramwellii），另一类为狭域生态特化种（高贵莲花掌 Ae. nobile），以此评估该岛屿上的演化潜力。两种物种的基因库分化与遗传多样性格局均与主要景观结构显著相关，蕴含系统地理学意义。不过，二者的整体遗传分化水平均偏低。针对广适种，异常位点检测与位点-环境关联分析方法显示，其存在与温度、降水变量相关的中度趋异选择压力信号；而特化种则未呈现此类演化模式。本研究结果表明，岛屿小尺度范围内的生态异质性与地形结构分化，可推动种群间的初期演化分化。此类过程极有可能推动了莲花掌属在加那利群岛（Canary Islands）的物种辐射演化。本研究还为广适种与特化种存在差异化演化机制提供了实证支持。