云南鹤庆晚上新世果实、种子化石及古环境研究

The study of fossil fruits and seeds (fossil carpology) is one of the key research areas in palaeobotany. It is well developed in European and North American countries, but has attracted much less attention in China. Recently, we found plenty of fossil fruits and seeds from the Sanying Formation of late Pliocene at Heqing County in northwestern Yunnan Province. These fossil fruits and seeds are three-dimensionally preserved and have diagnostic sculptures on the surface. Notably, they display a considerable diversity in taxa which include several herbaceous species. This is one of the few findings of fruit and seed fossil floras in China, and may give a good opportunity to conduct fossil carpological research.. In this project, we will collect abundant fossil fruits and seeds to cover almost all fossil taxa the flora may have, and then examine the fossils in morphology, surface micromorphology and anatomy, in order to identify them correctly and reliably. Based on the revealed floristic composition, we will interpret the palaeovegetation on the basis of the ecological features and growth forms of the taxa, and reconstruct its palaeoclimate by using the quantitative approach namely Coexistence Approach (CA). We will particularly focus on the diversity of herbaceous species in this flora and try to establish a new vegetation type from the late Pliocene of the Hengduan Mountains, which has herbaceous plants as its important elements. The correlation between the late Pliocene rise of herbaceous richness and palaeoenvironment will be looked at as well.

果实、种子化石研究（古果实学）是古植物学领域的重要组成部分，其在欧洲和北美发展成熟，但在国内相对薄弱。最近，申请人在云南鹤庆的晚上新世三营组地层中发现了大量果实、种子化石。这些化石具有三维立体结构，表面具有精美纹饰，且类群丰富，其中许多是草本植物，是国内果实、种子化石研究不可多得的材料。本项目拟系统采集果实、种子化石，利用形态学、微形态学和解剖学等分类性状，准确鉴定化石，从而认识植物群的区系组成，分析群落结构，重建古植被，并利用共存分析法定量重建古气候，讨论古植被和古气候的演变。本项目将着重研究该植物群的草本植物多样性，以此为例，探讨横断山地区晚上新世草本植物多样性的兴起和以草本植物为重要成分的植被类型的出现，并结合古气候和古环境，讨论草本植物多样性的兴起与气候、环境背景的关联。

横断山是我国乃至世界植物和植被多样性最丰富的地区之一，其中草本植物和草地植被多样性尤为丰富。目前，关于横断山草本植物多样性的兴起和草地植被的建立的研究主要依据分子生物学证据，而来自化石的证据稀少。产自横断山南部的鹤庆盆地晚上新世三营组地层的果实和种子化石植物群含大量草本成分，可能为揭示横断山草本植物多样性的兴起和草地植被的建立提供首个地史证据。本项目系统采集了该化石植物群的果实和种子化石，然后对化石进行了详细的形态学、微形态学和解剖学研究，并通过与现生植物的对比，准确鉴定化石。本项目共鉴定出22科28属，包括云杉属、铁杉属、松属、毛茛属、紫菫属、柯属、杨梅属、藜属、蓼属、酸模属、繁缕属、悬钩子属、草莓属、似黄芪属、柃属、乌蔹莓属、猕猴桃属、金丝桃属、杜鹃属、花椒属、飞龙掌血属、楤木属、大青属、接骨木属、睡菜属、紫菀属、苔草属和水葱属。这些植物涵盖乔木、灌木、藤本、草本和水生植物，可能反映了晚上新世鹤庆盆地及周边地区复杂的群落结构和多样的植被类型。由于亚热带和温带成分的共存，可能反映了盆地周边具有较大海拔落差的山地环境，亚热带成分可能分布于低海拔生境，而温带成分则分布于高海拔生境。草本植物丰富，包含10科12属，即毛茛属、紫菫属、藜属、蓼属、酸模属、繁缕属、草莓属、似黄芪属、睡菜属、紫菀属、苔草属和水葱属，认为晚上新世鹤庆盆地周边具有丰富的草本植物多样性和草地植被，基于分子生物学证据的中新世以来横断山草本植物的快速物种分化，可能增加了诸多草本类群在小范围内集聚的可能性。利用共存分析，定量估算了化石植物群所代表的古气候，发现温度和降水较现在高，推测自晚上新世以来，鹤庆盆地经历了变冷、变干的气候变化趋势，发现降水具有明显的季节性差异，夏季降水显著高于冬季降水，可能与亚洲季风气候的建立及增强有关。