基于DNA条形码从进化维度探讨热带森林群落的系统发育多样性

Global biodiversity is diminishing at an unprecedented rate due to anthropogenic changes in the environment. As this global biodiversity crisis continues, it is imperative to develop better ways to prioritize the distribution of limited conservation resources. Traditional diversity indices such as species richness have been used to assess biodiversity, but this method, based on species numbers, fails to capture this richness adequately and recent studies show that more comprehensive assessment methods that also include phylogenetic diversity (PD) are essential. This is because DNA sequence data can provide an evolutionary dimension to diversity estimates by incorporating genetic distance between species (i.e., phylogenetic branch lengths). Combined with DNA barcodes that provide universal markers for the species in a community or a region, genetic distance and thus phylogenetic diversity, can be quantified with and across ecological communities at varying geographic scales, providing better biodiversity estimates for conservation. .Using the tree DNA barcoding database developed during our recent MOST project, we will explore the application of phylodiversity measures to tropical areas of Yunnan with a focus on the highly diverse nature reserve in tropical Xishuangbanna. This study aims to create a four-marker DNA barcode library for the tree species in the nature reserve. These barcodes will enable a more sophisticated assessment of biodiversity in the reserve, using phylogenetic dissimilarity to quantify evolutionarily biodiversity at different scales..The study aims both to quantify forest biodiversity within the bioregion and to compare levels between sub-regions, as well as to contrast this approach with traditional methods for assessing forest diversity (species composition and richness and ecosystem diversity) in order to develop improved mechanisms for forest biodiversity conservation and management. The incorporation of PD metrics, along with traditional biodiversity indices for the national nature reserve will provide planners and decision makers with best-practice-derived information so that they can then select the best sites for protection by producing a quantifiable and comprehensive picture of the conservation value of an area at a genetic level..The use of phylodiversity measures in conservation assessments improve the evaluation of biodiversity by including two critical dimensions for conservation management: evolutionary history and total genetic richness for the target areas under study. Accordingly, this study will enhance significantly the application of PD to conservation policy and planning, improving decision making and leading to better long-term conservation outcomes.

本项目是申请人在长期从事植物系统发育研究、近期开展森林群落系统发育构建与物种共存机制探索，以及承担科技基础性工作专项积累大量DNA条形码数据的基础上，将进化思想与生物多样性保护的现实需求相结合，把物种进化历史纳入生物多样性保护实践中，将DNA条形码蕴含的物种间遗传距离融入到生物多样性评估中，从进化的维度进一步拓展完善生物多样性的评估体系。.项目拟以西双版纳自然保护区的热带森林群落为研究对象，依托野外生态观测站和森林动态监测样地，完善保护区树种DNA条形码数据；构建保护区物种水平的系统发育树；分析各子保护区的系统发育多样性、物种与系统发育多样性的相互关系，剖析系统发育多样性对物种多样性的残差，比较两者关系及残差在不同子保护区间分布的异同表现；将系统发育多样性纳入评估指标，结合环境因子，确立重点保护区域，优化完善现有保护策略，从进化角度为热带生物多样性保护提供深入合理的科学依据和可借鉴范例。

以西双版纳自然保护区的热带森林群落为研究对象，依托野外生态观测站和森林动态监测样地，完善保护区树种DNA条形码数据，构建了中国和国际贸易中1550种常用木材树种（隶属124科656个属）的DNA条形码数据库；利用多维度的生物多样性指标，如：物种多样性SR、系统发育多样性PD、标准化系统发育多样性PDses、系统发育结构NRI、物种进化特异性与威胁状态EDGE，从不同的森林植被类型（热带雨林、热带山地（低山）常绿阔叶林、热带季节性湿润林、热带季雨林）、不同的生长型（草本类群和木本类群）、受威胁的木本植物和重要类群樟科等多层次，分析西双版纳地区植物多样性的分布格局，评估生物多样性的保护状况，并且探索环境因子对其格局的影响。研究发现，热带雨林物种多样性与系统发育多样性均显著高于其他类型，热带森林植被的系统发育结构表现为聚集，推测其构建的主要方式为生境过滤；不同生长型的物种多样性分布格局和全部植物的物种多样性格局相似；多样性较高的区域主要分布在西双版纳西南部、东南部、中西部和中东部4个地方；气温和降水是影响木本植物多样性格局的主要因素，而土壤因素塑造了草本植物的多样性。此外，研究发现西双版纳地区受威胁乔木与樟科物种的系统发育多样性没有受到足够的保护；研究认为物种多样性虽然是评估优先保护区主要手段，但同时其它系统发育指标在优化保护区也至关重要，增加进化维度有助于识别新的重要区域和关键物种；同时指出，橡胶种植是西双版纳地区重要经济来源，但也是该地区生物多样性的主要威胁，西双版纳地区的保护策略应该考虑橡胶的实际情况，尽量满足生物多样性保护的最大化。通过确立重点保护区域，优化完善现有保护策略，从进化角度为热带生物多样性保护提供科学合理的依据和可借鉴范例。