Population Genetic Structure of <i>Glycyrrhiza inflata</i> B. (Fabaceae) Is Shaped by Habitat Fragmentation, Water Resources and Biological Characteristics

Background Habitat fragmentation, water resources and biological characteristics are important factors that shape the genetic structure and geographical distribution of desert plants. Analysis of the relationships between these factors and population genetic variation should help to determine the evolutionary potential and conservation strategies for genetic resources for desert plant populations. As a traditional Chinese herb, Glycyrrhiza inflata B. (Fabaceae) is restricted to the fragmented desert habitat in China and has undergone a dramatic decline due to long-term over-excavation. Determining the genetic structure of the G. inflata population and identifying a core collection could help with the development of strategies to conserve this species. Results We investigated the genetic variation of 25 G. inflata populations based on microsatellite markers. A high level of population genetic divergence (FST = 0.257), population bottlenecks, reduced gene flow and moderate genetic variation (HE = 0.383) were detected. The genetic distances between the populations significantly correlated with the geographical distances, and this suggests that habitat fragmentation has driven a special genetic structure of G. inflata in China through isolation by distance. STRUCTURE analysis showed that G. inflata populations were structured into three clusters and that the populations belonged to multiple water systems, which suggests that water resources were related to the genetic structure of G. inflata. In addition, the biological characteristics of the perennial species G. inflata, such as its long-lived seeds, asexual reproduction, and oasis ecology, may be related to its resistance to habitat fragmentation. A core collection of G. inflata, that included 57 accessions was further identified, which captured the main allelic diversity of G. inflata. Conclusions Recent habitat fragmentation has accelerated genetic divergence. The population genetic structure of G. inflata has been shaped by habitat fragmentation, water resources and biological characteristics. This genetic information and core collection will facilitate the conservation of wild germplasm and breeding of this Chinese medicinal plant.背景 生境破碎化、水资源与生物学特性是塑造荒漠植物遗传结构与地理分布格局的关键因素。解析上述因素与种群遗传变异间的关联，有助于明确荒漠植物种群的进化潜力与遗传资源保护策略。胀果甘草（Glycyrrhiza inflata B.，豆科Fabaceae）作为我国传统中药材，仅分布于碎片化的荒漠生境中，且因长期过度采挖出现种群数量急剧下降。明确胀果甘草种群的遗传结构并鉴定核心种质，可为该物种的保护策略制定提供助力。 研究结果 本研究基于微卫星（microsatellite）标记，对25个胀果甘草种群的遗传变异展开分析。检测到较高水平的种群遗传分化（FST = 0.257）、种群瓶颈效应、基因流降低以及中等程度的遗传变异（HE = 0.383）。种群间遗传距离与地理距离呈显著相关，表明生境破碎化通过距离隔离效应塑造了我国胀果甘草的独特遗传结构。STRUCTURE分析显示，胀果甘草种群可划分为3个遗传簇，且这些种群隶属于多个水系，提示水资源与胀果甘草的遗传结构密切相关。此外，作为多年生物种的胀果甘草，其生物学特性如长寿命种子、无性繁殖及绿洲生态适应性，可能与其抵御生境破碎化的能力相关。本研究进一步鉴定出包含57份材料的胀果甘草核心种质，该种质覆盖了胀果甘草的主要等位基因多样性。 结论 近期的生境破碎化加剧了种群遗传分化。胀果甘草的种群遗传结构由生境破碎化、水资源及生物学特性共同塑造。本研究获得的遗传信息与核心种质，将为这一国产药用植物的野生种质资源保护与品种选育工作提供有力支撑。