Harter David E V, Thiv Mike, Weig Alfons, Jentsch Anke, Beierkuhnlein Carl
Biogeography BayCEER University of Bayreuth Bayreuth Germany.
State Museum of Natural History Stuttgart Stuttgart Germany.
Ecol Evol. 2015 Sep 14;5(19):4327-44. doi: 10.1002/ece3.1682. eCollection 2015 Oct.
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.
景天科莲花掌属是海洋群岛上植物物种辐射的一个著名例子。然而，虽然该属在岛屿间的异域物种形成已有文献记载，但因地形隔离或生态异质性导致种群分化的岛内物种形成作用尚未得到探讨。本研究的目的是调查种内遗传结构，并确定岛屿尺度上遗传种群分化的空间和生态驱动因素。我们分析了拉帕尔马岛两种岛屿特有莲花掌属物种的简单序列重复区间变异：一种广泛分布的通才物种，覆盖多种不同的栖息地类型（大卫氏莲花掌），以及一种生态狭域特化物种（高贵莲花掌），以评估该岛上的进化潜力。两个物种的基因库分化和遗传多样性模式均与主要景观结构相关，具有系统地理学意义。然而，总体遗传分化水平较低。对于通才物种，异常位点检测和位点 - 环境相关性分析方法表明，存在与温度和降水变量相关的适度分歧选择压力特征，而特化物种则未出现此类模式。我们的数据表明种群间存在初始分化，强调岛屿小尺度内的生态异质性和地形结构可促进进化过程。很可能，这些过程促成了莲花掌属在加那利群岛的辐射。同时也支持通才物种和特化物种之间存在不同的进化机制。
