Data from: Evidence of local adaptation to fine- and coarse-grained environmental variability in Poa alpina in the Swiss Alps

1. In the alpine landscape, characterized by high spatiotemporal heterogeneity and barriers, divergent selection is likely to lead to local adaptation of plant populations either through adaptive genetic differentiation or phenotypic plasticity. The relative importance of these processes has rarely been investigated in relation to the spatial scale of environmental heterogeneity. In this study, we used reciprocal transplantation experiments of populations across nearby and distant field sites to shed light on these complementary processes. 2. We reciprocally transplanted populations of the widespread alpine grass, Poa alpina, within and across regions in the Swiss Alps. We inferred local adaptation at the meta-population level by comparing fitness of plants transplanted to their site of origin, and to nearby or distant novel sites. Additionally, we measured specific leaf area (SLA) and performed selection analyses to investigate directional selection on mean trait value at each field site, and on the degree of plasticity of this trait to assess if plastic responses were adaptive. In parallel, all populations were genotyped with microsatellite markers to assess neutral molecular differentiation. 3. Molecular differentiation was high among populations within and among regions, indicating restricted gene flow among P. alpina populations. Reproductive biomass was highest in individuals grown in their region of origin, revealing local adaptation to coarse-grained environmental variability. Similarly, inflorescence height, associated with reproductive biomass, reflected adaptation to fine- and coarse-grained environmental variability. Furthermore, we found evidence that plasticity in SLA across coarse-grained habitats was correlated with plant fitness, suggesting that plasticity in this trait is adaptive. 4. Synthesis Our results revealed adaptive genetic differentiation between P. alpina populations in the Swiss Alps reflecting local adaptation. Furthermore, high phenotypic plasticity in SLA contributed to the maintenance of fitness homeostasis across habitats. Hence, adaptive genetic differentiation and phenotypic plasticity play a complementary role for adaption of P. alpina to environmental heterogeneity in the Swiss Alps, and may both be critical to mitigate local extinction risk under rapid climate change.1. 在兼具高时空异质性与环境阻隔特征的山地景观中，歧化选择（divergent selection）极有可能通过适应性遗传分化或表型可塑性（phenotypic plasticity）驱动植物种群产生本地适应。目前鲜有研究结合环境异质性的空间尺度，探讨这两类适应过程的相对重要性。本研究通过在邻近与偏远野外样地间开展种群互易移植实验（reciprocal transplantation experiments），以期阐明这两类互补的适应机制。 2. 我们针对广泛分布的高山禾本科植物高山早熟禾（Poa alpina），在瑞士阿尔卑斯山的区域内部及跨区域范围内开展了种群互易移植实验。我们通过比较移植至原生境、邻近或偏远新生境植株的适合度（fitness），在集合种群（meta-population）水平推断本地适应情况。此外，我们测定了比叶面积（specific leaf area, SLA）并开展选择分析，以探究各野外样地中性状均值的定向选择，以及该性状的可塑性程度，以此评估可塑性响应是否具有适应性。与此同时，我们利用微卫星标记（microsatellite markers）对所有种群进行基因分型，以评估中性分子分化水平。 3. 区域内部及区域间的种群均存在较高的分子分化水平，表明高山早熟禾种群间的基因流受到限制。在原生区域生长的植株生殖生物量（reproductive biomass）最高，这表明种群对粗粒度环境异质性产生了本地适应。同样，与生殖生物量相关的花序高度（inflorescence height）也反映了种群对细粒度与粗粒度环境异质性的适应。此外，我们发现粗粒度生境下的比叶面积可塑性与植株适合度显著相关，表明该性状的可塑性具有适应性。 4. 综合分析：本研究结果表明，瑞士阿尔卑斯山高山早熟禾种群间存在适应性遗传分化，这正是本地适应的直观体现。此外，比叶面积的高表型可塑性有助于维持不同生境下的适合度稳态（fitness homeostasis）。因此，适应性遗传分化与表型可塑性在瑞士阿尔卑斯山高山早熟禾应对环境异质性的过程中发挥着互补作用，二者或许均对缓解快速气候变化下的本地灭绝风险具有关键意义。