Data from: Three keys to the radiation of angiosperms into freezing environments

Early flowering plants are thought to have been woody species restricted to warm habitats1, 2, 3. This lineage has since radiated into almost every climate, with manifold growth forms4. As angiosperms spread and climate changed, they evolved mechanisms to cope with episodic freezing. To explore the evolution of traits underpinning the ability to persist in freezing conditions, we assembled a large species-level database of growth habit (woody or herbaceous; 49,064 species), as well as leaf phenology (evergreen or deciduous), diameter of hydraulic conduits (that is, xylem vessels and tracheids) and climate occupancies (exposure to freezing). To model the evolution of species’ traits and climate occupancies, we combined these data with an unparalleled dated molecular phylogeny (32,223 species) for land plants. Here we show that woody clades successfully moved into freezing-prone environments by either possessing transport networks of small safe conduits5 and/or shutting down hydraulic function by dropping leaves during freezing. Herbaceous species largely avoided freezing periods by senescing cheaply constructed aboveground tissue. Growth habit has long been considered labile6, but we find that growth habit was less labile than climate occupancy. Additionally, freezing environments were largely filled by lineages that had already become herbs or, when remaining woody, already had small conduits (that is, the trait evolved before the climate occupancy). By contrast, most deciduous woody lineages had an evolutionary shift to seasonally shedding their leaves only after exposure to freezing (that is, the climate occupancy evolved before the trait). For angiosperms to inhabit novel cold environments they had to gain new structural and functional trait solutions; our results suggest that many of these solutions were probably acquired before their foray into the cold.

Usage Notes
Taxonomic lookup table containing clade-level mappings for 15,363 genera of Spermatophyta.Spermatophyta_Genera.csvGlobal Woodiness DatabaseGlobalWoodinessDatabase.csvPhylogenetic ResourcesThis archive contains datasets and resulting trees for maximum likelihood phylogeny reconstruction and time-scaling.PhylogeneticResources.zipGlobal Plant Species Freezing Exposure DatabaseThis collection of files documents the processing of the Global Biodiversity Information Facility (GBIF) geographic data and the WorldClim Bioclim data to produce a species freezing exposure datafile which is also included.climate.zipGlobal Leaf Phenology DatabaseGlobalLeafPhenologyDatabase.csv

早期开花的植物被认为是一种木质植物，它们局限于温暖的生境1, 2, 3。这一谱系随后辐射到几乎所有的气候区域，形成了多样的生长形态4。随着被子植物的扩散和气候的变化，它们进化出了应对间歇性冻结的机制。为了探索支撑在冻结条件下持续生存的性状的进化，我们构建了一个包含49,064个物种的生长习性（木质或草本；49,064种物种）以及叶片物候（常绿或落叶）、液压导管的直径（即木质部导管和管胞）和气候占有率的庞大物种水平数据库，以及暴露于冻结的条件。为了模拟物种性状和气候占有率的进化，我们将这些数据与一个无与伦比的时间标定的分子系统发育树（陆地植物32,223种）相结合。在此，我们展示木质类群通过拥有小型安全导管运输网络和/或通过在冻结期间落叶来关闭液压功能，成功地迁移到了易于冻结的环境中。草本物种主要通过衰老廉价的地上组织来避免冻结期。生长习性长期以来被视为易变的6，但我们的研究发现，生长习性的易变性小于气候占有率。此外，大部分冻结环境被那些已经变为草本或，即使保持木质，导管已经较小（即性状在气候占有率之前进化）的谱系所占据。相比之下，大多数落叶木质谱系在暴露于冻结之后才发生了季节性落叶的进化转变（即气候占有率在性状之前进化）。为了占据新的寒冷环境，被子植物必须获得新的结构和功能性状解决方案；我们的结果表明，许多这些解决方案可能在他们进入寒冷之前就已经获得。