早期陆生维管植物的形态多样性：华南泥盆纪植物化石记录的实例研究

Studies of morphological diversity are to estimate variations of organismal morphology in a constructed morphospace and to reveal macroevolutionary pattern of morphological characters, and thus such studies are of vital significance for a deeper understanding of the biodiversity evolution during geological history and have attracted increasing attentions. The colonization of land by early vascular plants has been considered to have a profound impact on the Earth System, and rapid evolution of morphological characters of these plants was certainly correlated with terrestrial environments at that time. However, the morphological diversity of Paleozoic plants has been poorly studied. Devonian plant fossils are abundant in the South China Block, where the fossil-bearing strata and plant taxonomy have been well-studied, and where most of the reported plants are endemic and well morphologically preserved; and therefore, the fossil record from South China provides a best object to study morphological diversity at the regional scale. The taxonomic diversity of Devonian vascular plants from South China had been studied in details, which for many plant groups shows an origination and diversification pattern, followed by an extinction, while their morphological diversity has not been fully revealed yet. Based on the rich fossil record from South China, this project aims to study the morphological diversity of early vascular plants, to reveal the evolutionary processes of some key traits during the colonization of the land, and to analyze the macroevolutionary pattern of plant morphologies. It is expected that such studies could provide evidence for understanding the mechanism of plant terrestrialization and their radiation.

形态多样性研究是通过测算生物表型在形态空间中的变化量，来阐述形态学特征的宏演化模式，因此对深入认识地史时期生物多样性演化具有重要意义，日益受到学术界关注。早期维管植物的成功登陆对地球系统产生了巨大影响，其形态学特征的快速演化与陆地环境存在紧密联系。然而，专门针对古生代植物类群的形态多样性研究却非常薄弱。华南板块泥盆纪植物化石标本丰富，地层学和分类学研究充分，多数植物形态特征较为完整，且存在大量的地方性属种，非常适合开展区域性的形态多样性研究。华南早期陆生维管植物的分类单元多样性已得到了较详细的阐述，多个植物类群显示了始现—繁盛—灭绝的宏演化模式，但形态多样性研究仍不完善。本项目拟以泥盆纪的陆生维管植物群为研究对象，应用定量统计方法，深入开展形态多样性研究，揭示植物登陆过程中一些关键形态学性状的演化，分析早期陆生维管植物形态的宏演化模式，以期为解释植物成功登陆和辐射演化的机制提供科学依据。

志留至泥盆纪是陆生维管植物演化的关键阶段，维管植物的成功登陆对后续陆地生物和生态系统的演化产生了深远的影响；植物在泥盆纪的辐射演化被认为是可与寒武纪海洋动物大爆发相比拟的陆地事件。形态多样性关注表型（生物大小、形态和复杂度等）在形态空间中的变化量，是研究生物宏演化的一项重要内容。在本项目资助下，我们建立了我国晚古生代陆地维管植物分类单元和形态单元数据集。通过对我国华南板块志留纪至泥盆纪陆地维管植物81属108种的形态特征（包括最大茎轴直径、孢子囊大小，营养叶片长度、宽度等）进行编码，揭示了华南板块维管植物表型宏演化的规律，表现为茎轴宽度和叶片大小呈现出阶段性演化模式，而孢子囊的大小变异在泥盆纪早期达到最大值，在中、晚期萎缩，体现为早期爆发模式。同时，研究发现楔叶类植物的叶面积由小变大，叶片由深裂至不裂，叶尖形状由分裂变为圆形或钝圆，叶轮中的叶由大小相等到大小不等，并出现叶镶嵌，这可能与当时植物群落中林下层光照强度的变化有关。此外，本项目进一步拓展研究了华北板块陆地植物二叠纪至中三叠世的多样性变化。目前，已经发表SCI论文2篇，分别为Earth-Science Reviews（Xiong et al., 2021，1区TOP，本项目为第一标注），Historical Biology（Wang et al., 2019，本项目为第二标注），以及EI期刊论文1篇和核心期刊论文4篇（本项目均为第一标注），获批国家发明专利1项，超额完成了预定任务。