Data from: The roles of geography and environment in divergence within and between two closely related plant species inhabiting an island-like habitat

Aim: In island-like habitats, geographic isolation facilitates population and species divergence by constraining gene flow, while environmental isolation can enhance divergence. We tested the relative contribution of geographic and environmental isolation in genetic and phenotypic divergence within and between two species of the figwort Ameroglossum (Scrophulariaceae) inhabiting spatially isolated habitats, known as inselbergs.
Location: Borborema Plateau, north-eastern Brazil.
Methods: Multivariate models of redundancy (RDAs) and partial redundancy analyses (pRDAs) were used to partition the geographic and climate components of genetic variation in 48 microsatellite alleles, and phenotypic variation in 11 leaf and flower traits. We also used linear mixed-effect models (LMEs) to test independent associations of floral tube length variation among inselbergs with local pollinator phenotypes, climate and geography. In each approach, we analysed the data for each species separately and in pooled models for both species.
Results: RDAs revealed that genetic variation within and between the species of Ameroglossum was associated similarly with geography and climate. Phenotypic variation within A. manoel-felixii and between species was also associated similarly with geography and climate but, within A. pernambucense, phenotype was more strongly associated with climate. Linear mixed-effect models revealed that flower divergence in A. manoel-felixii was associated only with the bill length of local hummingbirds, whereas floral variation in A. pernambucense was associated with geography, bill length and climate. Only climate was associated with flower divergence between species.
Main conclusions: Genetic and phenotypic variation in Ameroglossum are associated with geographic and environmental isolation. These findings indicate a significant role of ecological factors shaping plant divergence among inselbergs, irrespective of their spatial distances.

研究目的：在类岛屿生境中，地理隔离通过限制基因流（gene flow）促进种群与物种分化，而环境隔离可进一步强化这一分化过程。本研究针对栖息于被称为岛山（inselbergs）的空间隔离生境中的两种隶属于玄参科（Scrophulariaceae）的Ameroglossum属植物，检验了地理隔离与环境隔离在种群及物种间的遗传与表型分化中的相对贡献。
研究地点：巴西东北部博博雷马高原（Borborema Plateau）。
研究方法：本研究采用冗余分析（RDA，Multivariate models of redundancy）与偏冗余分析（pRDA，partial redundancy analyses），对48个微卫星等位基因（microsatellite alleles）的遗传变异以及11个叶部与花部性状的表型变异中的地理与气候组分进行分区解析。此外，本研究采用线性混合效应模型（LMEs，linear mixed-effect models），检验了不同岛山之间花管长度变异与当地传粉者表型、气候及地理的独立关联。在每种分析框架下，我们分别针对两个物种进行数据分析，并针对两个物种的合并数据构建模型开展分析。
研究结果：冗余分析结果显示，Ameroglossum属内物种间及物种内的遗传变异，均与地理及气候因素呈现相似的相关性。A. manoel-felixii的种内表型变异以及物种间的表型变异，同样与地理及气候因素呈现相似相关性；但在A. pernambucense中，表型变异与气候因素的关联更为显著。线性混合效应模型分析结果显示：A. manoel-felixii的花部分化仅与当地蜂鸟的喙长相关，而A. pernambucense的花部变异则与地理因素、喙长及气候均相关；物种间的花部分化仅与气候因素相关。
主要结论：Ameroglossum属植物的遗传与表型变异，均与地理隔离及环境隔离相关。本研究结果表明，无论空间距离如何，生态因素在岛山生境中的植物分化过程中均发挥着重要作用。