Reconstructing the origins of high-alpine niches and cushion life form in the genus Androsace s.l. (Primulaceae)

Relatively few species have been able to colonize extremely cold alpine environments. We investigate the role played by the cushion life form in the evolution of climatic niches in the plant genus Androsace s.l., which spreads across the mountain ranges of the Northern Hemisphere. Using robust methods that account for phylogenetic uncertainty, intraspecific variability of climatic requirements and different life history evolution scenarios, we show that climatic niches of Androsace s.l. exhibit low phylogenetic signal and that they evolved relatively recently and punctually. Models of niche evolution fitted onto phylogenies show that the cushion life form has been a key innovation providing the opportunity to occupy extremely cold environments, thus contributing to rapid climatic niche diversification in the genus Androsace. We then propose a plausible scenario for the adaptation of plants to alpine habitats.仅有极少数物种能够成功拓殖极端寒冷的高山环境。本研究以广泛分布于北半球各大山系的广义点地梅属（Androsace s.l.）植物类群为研究对象，探讨垫状生活型（cushion life form）在其气候生态位（climatic niches）演化过程中所发挥的作用。本研究采用考虑了系统发育不确定性（phylogenetic uncertainty）、气候需求的种内变异（intraspecific variability of climatic requirements）以及不同生活史演化情景的稳健分析方法，结果显示：广义点地梅属的气候生态位表现出较低的系统发育信号（phylogenetic signal），且其演化时间相对较近且呈间断式。拟合于系统发育树的生态位演化模型结果表明，垫状生活型是一类关键创新性状，为类群占据极端寒冷环境提供了演化契机，进而推动了广义点地梅属快速的气候生态位分化（climatic niche diversification）。本研究最后提出了一套合理的植物适应高山生境的演化情景。