单瓣月季花和亮叶月季的种间分化及保护遗传学研究

Rosa chinensis Jacq. var. spontanea (Rehd. et Wils.) Yü et Ku and R. lucidissima Lévl. are two endemic rose species to China in the section Chinenses DC. with similar morphology and tangling phylogeny. Both species might be key ancestors of modern rose and are important for studying the genetics and breeding of rose. However, R. chinensis var. spontanea is now in endangered risk and R. lucidissima is in critically endangered risk. It is necessary to untangle their systematic relationship on one hand and to carry out conservation genetic study on the other. Their distribution and population status have been investigated and specimens and plant materials of those populations have been collected during our field investigation. Accordingly, supplementary investigation will be carried out to understand its true threatened status in the wild. Some phenotypic traits and a large amount of SNPs from double-digested restriction site associated DNA sequencing (ddRADSeq) will be used to study the genetic variation within each species and the interspecific differentiation between them. The genetic diversity and genetic structure of each species or the possible complex composed by both species will be analyzed. Then, their population history and possible threatened mechanism will be postulated and the key populations or the evolutionary significant units, ESUs, will be determined. According to the survival status and genetic background, some conservation strategies will be brought forward. Meanwhile, the propagation materials of the key populations and special individuals with significant traits will be collected for ex-situ preservation in Kunming. The results will not only benefit the efficient conservation and utilization of R. chinensis var. spontanea and R. lucidissim, but also provide some important plant materials for further study on rose genetics and breeding. Moreover, it will also supply population genetic data for the origin and systematics of the genus Rosa.

单瓣月季花和亮叶月季是中国特有的蔷薇属月季组植物，二者在形态上极为相似，在已有的分子系统树上也难以分开，都可能是现代月季的重要原始亲本，是月季遗传育种研究需要的重要资源，然而已分别处于“濒危”和“极危”状态，急需弄清二者的相互关系并开展保护遗传学研究。项目通过前期调查基本掌握了二者的分布和种群现状并获得了大量的标本和实验材料，拟通过补充调查了解其真实的受威胁情况；利用表型性状和基于双酶切简化基因组测序（ddRADSeq）的大量SNPs位点开展两个种的种内和种间分化研究；弄清二者或二者所构复合群的遗传多样性和遗传结构；推断种群历史及受威胁的机制，确定关键居群或显著进化单元，结合种群现状提出相应的保护措施。研究结果不仅有利于对这两种蔷薇的保护和利用，为月季遗传育种研究提供材料，还可为蔷薇属植物的起源和系统发育研究提供居群遗传学数据。

项目对单瓣月季花和亮叶月季这两种在形态上相似、分类上存疑且已分别处于“濒危”和“极危”的蔷薇属植物进行了种群现状调查和繁育系统研究，完成了基于表型和RAD-seq的系统关系、种间分化和保护遗传学研究，明确其濒危机制并提出保护措施。结果如下：（1）单瓣月季花-亮叶月季复合群主要分布在北至甘肃文县、南至广西龙州、东至广东封开、西至四川天全，海拔193m- 1573m的亚热带季风气候区。现存居群均较小，生境主要为向阳的杂木林缘及灌丛。花期3月初-5月初，进化出了如柱头短于雄蕊、开放过程中花色变化等特性，形成了异交和兼性异交等多样化的繁育系统。（2）两个物种在形态上高度相似，表型分析未能将其分为两个种，但基于RAD-seq检测到的92,492个有效SNPs，ML系统发育树、邻接网状进化树和群体指派分析均将全部个体和居群分为两大支。建议将单瓣月季花和亮叶月季仍独立为两个种：四川盆地及其周围山地的居群属于单瓣月季花，云贵高原及其南部居群包括贵州北部与四川盆地东南缘过渡的仁怀、彭水、南川、酉阳等均属于亮叶月季。（3）两个物种的遗传多样性都较低，居群间存在较高的遗传分化和近交。单瓣月季花的P、Ho、He、π和Fis分别为3039、0.1287、0.1683、0.1698和0.6096，69.10%的遗传变异来源于居群间；亮叶月季相应的参数分别为2721、0.1362、0.1758、0.178和0.5989，78.00%的遗传变异来源于居群间。（4）亮叶月季在1.21-0.86Mya形成于云贵高原东南部及其邻近地区并在此度过第四纪气候振荡，单瓣月季花的祖先于0.022-0.031Mya在云贵高原东北与四川盆地东南缘过渡的大娄山和武陵山等地从亮叶月季分化出来，并在此度过末次大冰期。两个种均没有显著的谱系地理结构，均没有经历过快速种群扩张。（5）单瓣月季花和亮叶月季濒危的内在机制是遗传多样性低及近交衰退。自然群落荫蔽度增加、人为采挖和发展人工植被等造成的生境片段化及种群减小进一步加剧了遗传多样性降低和近交衰退。建议重点保护平武、苍溪、雷波、南江、巴东和奉节等单瓣月季花居群和除瓮安和施秉外的所有亮叶月季居群，提出就地建立微型保护区和异地建立资源圃等措施。上述研究结果不仅有利于单瓣月季花和亮叶月季的种质资源保护和开发利用，还可为蔷薇属植物的系统发育研究提供佐证。