广东省中山市五桂山土沉香遗传多样性

Genetic diversity of Aquilaria sinensis in Wuguishan, Zhongshan, Guangdong Province

关键词:  瓶颈效应, 亲缘关系, 微卫星体, 遗传变异, 种群扩张

Key words:  bottleneck effects, genetic relationship, microsatellites, genetic variation, population expansion

摘要:

土沉香(Aquilaria sinensis)是生产中药沉香的重要树种,现被列为国家二级重点保护野生植物。该研究通过采集该地区83株土沉香样品,利用限制性酶切位点相关DNA测序(restriction site-associated DNA sequencing,RAD-seq)方法获得的18个微卫星体作为分子标记,计算了五桂山土沉香种群的整体观测杂合度(observed-heterozygosity)、期望杂合度(expected-heterozygosity)、种群整体近交系数及其个体间的亲缘关系,并对种群可能经历的种群缩小或种群扩张状况进行了分析。结果表明:与同属其它物种以及同一生活史物种相比,五桂山地区土沉香遗传多样性略低(观测杂合度和期望杂合度分别为0.523和0.522),但种群整体处于随机交配状态(近交系数为-0.002)。瓶颈效应分析表明该种群没有经历瓶颈效应,且81.810%的个体间无亲缘关系,说明这一地区土沉香并非少数个体发育起来; 种群扩张分析表明其种群大小有增长情形。综合这些结果可以看出,中山市五桂山土沉香种群整体遗传健康状况良好,较好地保存了该区域种质资源遗传多样性,为今后的保护和合理开发提供了优质资源储备

Abstract:

Aquilaria sinensis, famous of its fragrant wood, is listed as national Level Ⅱ protected wild plants. For sound conservation this precious population of A. sinensis in Wuguishan District of Zhongshan City, we conducted genetic diversity surveys on it. Because population history such as shrinking or expansion would definitely leave signatures in population genetic variations, based on the genetic diversity investigated in Wuguishan population of A. sinensis, we also made population history inferences for it. Among genetic diversity studies, microsatellite markers are the most suitable tools due to their high polymorphism. Therefore, using eighteen microsatellites obtained by restriction site-associated DNA sequencing(RAD-seq), we examined the genetic diversities of 83 A. sinensis individuals collected from Wuguishan District, and estimated genetic diversity parameters by observed-heterozygosity, expected-heterozygosity and inbreeding index. Because the genetic relationship between individuals could reflect whether Wuguishan population of A. sinensis was derived from a few ancestors, pairwise genetic relatedness was calculated and four types of relationship(parent-offspring, full-siblings, half-siblings and unrelated)between individuals were determined. The population history was inferred for population shrinking(bottleneck)or expansion. Overall, compared to the genetic variation of the species in the same genus and the species with similar life history traits, the genetic diversity in Wuguishan population was slightly low with the observed-heterozygosity and expected-heterozygosity being 0.523 and 0.522, respectively. The value of -0.002 for inbreeding index, which was close to zero, indicated that the whole population was under random mating. Bottleneck analysis indicated bottleneck effects did not happened recently in Wuguishan population, which meant no population shrinking. Pairwise relationships between individuals confirmed this by showing most of individual pairs(>81.810%)were unrelated. Finally, we detected the evidence of population expansion on the basis of allele size distributions. Accordingly, these results indicated that Wuguishan population of A. sinensis is generally genetically healthy. Such information provides the reference for the conservation and the reasonable uses of A. sinensis in the future.