横断山晚上新世裸子植物多样性的研究

The Hengduan Mountains, located in the southeastern edge of the Qinghai-Tibetan Plateau, represents one of the plant diversity hotspots in China or even in the world. The modern diversity and distributional patterns of plants there are largely affected by the dramatic environmental changes during the geological past there. Hence, it is an ideal area for studying the evolution and formation of such modern plant diversity. However, previous interests have mainly been shown in angiosperms, whereas gymnosperms have rarely been investigated regarding the establishment of their modern diversity in the Hengduan Mountains. Recently, we found plenty of fossil cones, seed scales and small leaves of some conifers from three late Pliocene fossil floras namely Nanbanbang, Fudong and Qingfu within the Hengduan Mountains. These fossils are well-preserved, most of them being three-dimensional. Our preliminary identification demonstrates they may include several different taxa of conifers. Hence they are crucial evidence to answer the evolution and establishment of the coniferous or even gymnospermous diversity in the Hengduan Mountains. . In this project, we will collect more abundant fossil materials from the three fossil floras mentioned above, to cover almost all coniferous taxa the three floras may have. We then examined the fossils in morphology, surface micro-morphology and anatomy, in order to identify them correctly. Based on our credible taxonomy, we will present the gymnospermous diversity in the Hengduan Mountains during the late Pliocene. We will also interpret the diversity evolution of conifers in this region since the late Pliocene, and thus understand the formation of modern coniferous richness in the Hengduan Mountains. Finally, we will discuss the link between the late Pliocene coniferous diversity and dramatic environmental changes in the Hengduan Mountains.

横断山地处青藏高原东南缘，为全球植物多样性热点地区之一，其现代植物的物种多样性及分布格局极大地受到了该地区地史时期发生的剧烈地质、气候等环境变迁，因而是研究植物多样性形成与演化的理想地域。然而，以往研究主要集中于被子植物多样性的形成与演化，而裸子植物在该地区的多样性演化知之尚少。最近，申请人在地处横断山腹地的南班榜、福东和庆福3个晚上新世植物群中采集了一批保存完好、大部分具有三维立体结构的松柏类植物的球果、种鳞和叶片化石，是研究横断山松柏类甚至裸子植物物种多样性形成和演化的重要地史依据。本项目拟在前期材料采集的基础上，进一步补充研究材料，通过形态学、微形态学和解剖学等分类学研究手段，准确鉴定化石，从而揭示横断山晚上新世裸子植物的物种多样性，理解现在横断山裸子植物多样性的建立，并讨论其与新近纪该地区剧烈的地质、气候等环境变化的关联。

横断山地处青藏高原东南缘，为裸子植物物种多样性重要的分布中心及分化中心，然而对于裸子植物在该地区丰富物种多样性的形成与演化知之甚少。植物化石作为植物历史存在的直接证据，能够为解释该科学问题提供重要的地史证据。在横断山腹地的南班榜、福东和庆福3个晚上新世植物群中采集的丰富裸子植物化石为理想的研究材料。本项目拟通过研究这些植物群中的裸子植物化石，基本认识横断山地区晚上新世时期裸子植物的多样性，理解横断山地区现代裸子植物多样性的形成与演化及其可能的地质及气候因素。经过对这些材料进行系统的形态学、微形态学及解剖学研究，并与现生类群进行对比，确定了它们的系统学分类位置，综合分析表明横断山地区晚上新世时期的裸子植物以松科松属、云杉属、冷杉属、铁杉属以及柏科柏木亚科类群为主，其中松属类群又分化出了前思茅松、云南松、高山松及华山松等类群，表明横断山地区晚上新世时期裸子植物尤以松柏类类群已具有很高的物种多样性，且晚上新世可能为这些类群快速分化的重要时期，逐步形成了较高海拔处的混合针叶林植被类型。此外，研究结果还表明，横断山南部在晚上新世时期很可能为高山或多山地质环境，且气候较为温暖；该地区复杂的地形地貌及多样的气候环境可能为松柏类的物种分化提供了有利条件。该地区的古地质及古气候环境条件研究结果，也得到了植物群中其他共存被子植物化石研究结果的印证。