云南特有易危植物中甸刺玫的种群现状及保护遗传学研究

Rosa praelucens Byhouwer is one of the endemic Rosa species to Yunnan. It is an important rose germplasm resource highly tolerant to coldness and a famous alpine ornamental plant. With its characteristics of decaploidy and narrow distribution, it is also a very interesting material for theoretical study in biology. Only found at less than 5 plots and very narrowly distributed, R. praelucens is classified as 'vulnerable' plant in China Species Red List and it is urgent to carry out some proper conservation strategies to prevent it from extinction. However, the survival status and genetic background attributing to its vulnerability are hardly known to people. On the basis of primary knowledge of its distribution and population size after years of field investigation, this study will carry out a further systematic field investigation on its habitats, distribution, population size, reproduction characters, population regeneration and demographic characters. At the same time, studies on the conservation genetics including the genetic diversity, population genetic differentiation and genetic structure of R. praelucens will be carried out based on 44 phenotypic traits, fluorescent Amplified Fragment Length Polymorphism (fluorescent-AFLP) and 2 chloroplast loci variation. According to the survival status and genetic background, the Evolutionary significant unit (ESU) of R. praelucens will be determined and some conservation strategies will be brought forward. The results will not only benefit the efficient conservation and utilization of R. praelucens, but also supply population genetic data for the study of its origin, systematics, reproduction and dispersal mechanisms. Furthermore, it will also become the reference to the conservation and utilization of other vulnerable and endangered Rosa species.

中甸刺玫是云南特有的蔷薇属植物之一，也是耐低温的月季种质资源和著名的高山花卉。10倍体特征和狭窄的分布范围使之成为重要的理论研究材料。因"分布地点少且狭窄"，中甸刺玫被《中国物种红色名录》列为"易危"植物，急需采取正确的保护措施，但目前我们对其生存现状和易危的遗传背景并不清楚。项目在初步掌握了中甸刺玫的分布和种群大小的基础上，拟通过全面系统的种群现状调查掌握其生境、分布、群体数量、繁育特征、植株更新、生长状况及种群年龄结构。同时开展保护遗传学研究，利用44个表型性状、6对荧光AFLP分子标记和2个叶绿体基因片断研究其遗传多样性、遗传分化和遗传结构。根据种群现状及保护遗传学背景，推测其易危的可能原因，确定进化显著单元(ESU)并提出相应的保护措施。研究结果不仅有利于中甸刺玫种质资源的有效保护利用，为研究其起源、系统发育和繁殖传播机制提供居群遗传学数据，还可为蔷薇属其它植物的保护利用提供借鉴。

本项目对云南特有且已处于“易危”状态的中甸刺玫进行了种群现状调查和繁殖特性研究，完成了基于23个表型性状、3个cpDNA片段和6对AFLP分子标记的保护遗传学研究，推测了其受威胁的原因并提出了相应的保护措施。结果如下：1）中甸刺玫仅分布在小中甸镇沿硕多岗河约250km2的狭窄范围内，野外仅存623株(含61株幼苗)且多数分布点无更新，年龄结构在长远来说处于衰退状态，确证应将其受威胁等级由“易危”上升为“极危”。2）中甸刺玫是虫媒植物，不能进行无融合生殖和自动自花传粉，为适应高海拔生境的传粉限制进化出了异交和同株异花自交的混合型繁育系统。3）中甸刺玫表型变异丰富，23个性状的平均分化系数为69.56%；中甸刺玫具有较高的遗传多样性（hT cpDNA=0.720）和遗传分化(Gst cpDNA=0.539, Gst AFLPs=0.567)，可能由其克隆生长、高倍性、混合型的繁育系统以及较低的基因交流（Nm cpDNA=0.214, Nm AFLPs=0.382）等特性所致。现存所有个体基于AFLPs的聚类结果与植株花形态特别是花色相一致。4）中甸刺玫“极危”不是由于遗传多样性低，而是由于生境片断化和自身有性繁殖困难所致。那些拥有“独享”单倍型的居群（胡批、布呵谷等）以及贡献了较高的cpDNA遗传多样性且拥有较多的AFLP基因型的居群（桃木谷、祝公，肯古、昌都学、热水塘、都日谷等），应通过建立“植物微型保护区”的形式得到优先“就地”保护。高山植物园和祝公苗圃已分别保存的1个“独享”单倍型，建议在“迁地”保护中加以重视，通过人工扩繁后用于今后的种群恢复中。项目的研究结果不仅有利于中甸刺玫的保护，还为研究其起源和形成提供了遗传背景资料，也为进一步开发利用中甸刺玫奠定了繁殖生物学基础和种苗扩繁的技术基础。