丹霞梧桐(Firmiana danxiaensis)是分布于我国韶关地区北部丹霞地貌的特有物种, 其分布范围狭窄, 种群数量小。本文利用EST-SSR分子标记位点, 分析丹霞梧桐群体(丹霞山组群和南雄组群)的遗传多样性和遗传结构, 研究群体的分化历史, 探讨该物种的可能分布和科学保护策略。结果表明: 丹霞梧桐总的遗传多样性中等(Ht = 0.631), 群体内遗传多样性较高(Hs = 0.546), 遗传变异主要存在于群体内(79.66%), 但不同地理组群间存在显著的遗传分化(F_ST = 0.150)。长期地理隔离和现代人为干扰是形成丹霞梧桐当前遗传变异模式的主要原因。STRUCTURE分析可将研究群体划分为清晰的两个基因库(gene pool), 其遗传结构与系统发育地理格局之间有密切关系。丹霞梧桐不同地理群体经历了独立的进化路线, 但丹霞山群体的杂合性高, 遗传背景更为复杂。近似贝叶斯运算法(Approximate Bayesian Computation, ABC)分析表明, 丹霞山和南雄地理群体在10万年前由同一个祖先群体分化而来, 分化时有效群体大小分别为7,290和5,550。结合丹霞梧桐的遗传变异和生态位信息, 可推测丹霞梧桐曾广泛分布于南岭地区, 受第四纪第三次亚冰期的影响, 南岭北部的丹霞梧桐群体因气候剧烈变化而灭绝, 仅在南岭南部适宜的环境中得以保存并繁衍至今, 丹霞山和南雄是丹霞梧桐最主要的两个冰期避难所。在全面掌握丹霞梧桐的自然分布, 开展就地保护的基础上, 通过建立种质资源圃、人工种苗扩繁、自然回归试验等措施, 对于该物种的异地保护、种群恢复和开发利用具有重要意义。

Firmiana danxiaensis is an endemic plant species which is narrowly distributed in the northern parts of Shaoguan, Guangdong, China. To devise appropriate conservation strategies for this rare species, we examined the population structure and estimated the demographic history of nine natural populations using 18 EST-SSR markers. The results revealed a moderate degree of total genetic diversity (Ht = 0.631) at the species level but high genetic diversity within populations (Hs = 0.546). Strong genetic differentiation existed between two groups of Danxiashan and Nanxiong (F_ST = 0.150). This current pattern might have arisen from prolonged geographical isolation and human disturbances. STRUCTURE analysis demonstrated that whole population can be divided into two distinct gene pools, closely related by their geographic location and having experienced independent evolutionary routes. The genetic background of Danxiashan was more complicated than that of Nanxiong. Approximate Bayesian Computation (ABC) analysis indicated that divergence time between the two groups could be 100,000 years BP, and their effective population size were 7,290 and 5,550 individuals, respectively. Combining the information of genetic variation with niche modelling, we inferred that F. danxiaensis might have been widely distributed around the Nanling Mountain in the Quaternary period. Populations located in the northern of Nanling Mountain likely became extinct due to climate change. Danxiashan and Nanxiong provided the main refuges for the species during the last ice age. Being a rare species with small population sizes, better ecological investigation of natural populations and in situ conservation and implementation of restoration strategy are important measures to conserve this species.