Institute of Botany, University of Basel, Schönbeinstr. 6, CH-4056 Basel, Switzerland.
Ann Bot. 2009 Dec;104(7):1313-22. doi: 10.1093/aob/mcp242. Epub 2009 Oct 1.
Gene flow and genetic variability within and among alpine plant populations can be greatly influenced by the steep environmental gradients and heterogeneous topography of alpine landscapes. In this study, the effects are examined of natural isolation of alpine habitats on genetic diversity and geographic structure in populations of C. thyrsoides, a rare and isolated European Alpine monocarpic perennial with limited seed dispersal capacity.
Molecular diversity was analysed for 736 individuals from 32 populations in the Swiss Alps and adjacent Jura mountains using five polymorphic microsatellite loci. Pollen flow was estimated using pollen grain-sized fluorescent powder. In addition, individual-based Bayesian approaches were applied to examine population structure.
High within-population genetic diversity (H(E) = 0.76) and a relatively low inbreeding coefficient (F(IS) = 0.022) were found. Genetic differentiation among populations measured with a standardized measure was considerable (G'(ST) = 0.53). A significant isolation-by-distance relationship was found (r = 0.62, P < 0.001) and a significant geographic sub-structure, coinciding with proposed postglacial migration patterns. Altitudinal location and size of populations did not influence molecular variation. Direct measures of pollen flow revealed that insect-mediated pollen dispersal was restricted to short distances within a population.
The natural isolation of suitable habitats for C. thyrsoides restricts gene flow among the populations as expected for a monocarpic species with very limited seed dispersal capacities. The observed high within-population genetic diversity in this rare monocarpic perennial is best explained by its outcrossing behaviour, long-lived individuals and overlapping generations. Despite the high within-population genetic diversity, the considerable genetic differentiation and the clear western-eastern differentiation in this species merits consideration in future conservation efforts.
高山植物种群内和种群间的基因流动和遗传变异受高山景观陡峭的环境梯度和异质地形的极大影响。在这项研究中，考察了高山生境的自然隔离对 C. thyrsoides 种群遗传多样性和地理结构的影响，C. thyrsoides 是一种罕见的、孤立的欧洲高山单年生多年生植物，其种子传播能力有限。
利用 5 个多态性微卫星位点，对来自瑞士阿尔卑斯山和相邻汝拉山 32 个种群的 736 个个体进行了分子多样性分析。花粉流通过花粉粒大小的荧光粉进行估算。此外，还应用基于个体的贝叶斯方法来检验种群结构。
发现种群内遗传多样性较高（H(E) = 0.76），近交系数较低（F(IS) = 0.022）。用标准化方法测量的种群间遗传分化相当大（G'(ST) = 0.53）。发现存在显著的隔离距离关系（r = 0.62，P < 0.001）和显著的地理亚结构，与推测的冰川后迁移模式一致。海拔位置和种群大小均不影响分子变异。花粉流的直接测量表明，昆虫介导的花粉传播在种群内的短距离内受到限制。
C. thyrsoides 适宜生境的自然隔离限制了种群间的基因流动，这与具有非常有限种子传播能力的单年生植物相符。在这种罕见的单年生多年生植物中，观察到的高种群内遗传多样性最好用其异交行为、长寿命个体和重叠世代来解释。尽管种群内遗传多样性较高，但该物种遗传分化程度较高，东西部分化明显，值得在未来的保护工作中加以考虑。
