Chung Mi Yoon, Nason John D, Chung Myong Gi
Department of Biology and Institute of Basic Science, Gyeongsang National University, Jinju 660-701, South Korea.
Mol Ecol. 2007 Jul;16(13):2816-29. doi: 10.1111/j.1365-294X.2007.03361.x.
Spatial genetic structure within plant populations is influenced by variation in demographic processes through space and time, including a population's successional status. To determine how demographic structure and fine-scale genetic structure (FSGS) change with stages in a population's successional history, we studied Hemerocallis thunbergii (Liliaceae), a nocturnal flowering and hawkmoth-pollinated herbaceous perennial with rapid population turnover dynamics. We examined nine populations assigned to three successive stages of population succession: expansion, maturation, and senescence. We developed stage-specific expectations for within-population demographic and genetic structure, and then for each population quantified the spatial aggregation of individuals and genotypes using spatial autocorrelation methods (nonaccumulative O-ring and kinship statistics, respectively), and at the landscape level measured inbreeding and genetic structure using Wright's F-statistics. Analyses using the O-ring statistic revealed significant aggregation of individuals at short spatial scales in expanding and senescing populations, in particular, which may reflect restricted seed dispersal around maternal individuals combined with relatively low local population densities at these stages. Significant FSGS was found for three of four expanding, no mature, and only one senescing population, a pattern generally consistent with expectations of successional processes. Although allozyme genetic diversity was high within populations (mean %P = 78.9 and H(E) = 0.281), landscape-level differentiation among sites was also high (F(ST) = 0.166) and all populations exhibited a significant deficit of heterozygotes relative to Hardy-Weinberg expectations (range F = 0.201-0.424, mean F(IS) = 0.321). Within populations, F was not correlated with the degree of FSGS, thus suggesting inbreeding due primarily to selfing as opposed to mating among close relatives in spatially structured populations. Our results demonstrate considerable variation in the spatial distribution of individuals and patterns and magnitude of FSGS in H. thunbergii populations across the landscape. This variation is generally consistent with succession-stage-specific differences in ecological processes operating within these populations.
植物种群内部的空间遗传结构受到人口统计学过程在时空上变化的影响，包括种群的演替状态。为了确定人口统计学结构和精细尺度遗传结构（FSGS）如何随着种群演替历史的阶段而变化，我们研究了萱草（百合科），一种夜间开花、由天蛾传粉的多年生草本植物，其种群更替动态迅速。我们研究了九个种群，它们被分为种群演替的三个连续阶段：扩张、成熟和衰老。我们针对种群内部的人口统计学和遗传结构制定了特定阶段的预期，然后使用空间自相关方法（分别为非累积O环统计和亲属关系统计）对每个种群中个体和基因型的空间聚集进行量化，并在景观水平上使用赖特F统计量测量近交和遗传结构。使用O环统计的分析表明，在扩张和衰老种群中，个体在短空间尺度上有显著聚集，这尤其可能反映出种子在母本个体周围的扩散受限，以及这些阶段相对较低的当地种群密度。在四个扩张种群中的三个、没有成熟种群以及只有一个衰老种群中发现了显著的FSGS，这一模式总体上与演替过程的预期一致。尽管种群内等位酶遗传多样性较高（平均%P = 78.9，H(E) = 0.281），但地点间的景观水平分化也较高（F(ST) = 0.166），并且所有种群相对于哈迪-温伯格预期都表现出显著的杂合子亏缺（范围F = 0.201 - 0.424，平均F(IS) = 0.321）。在种群内部，F与FSGS的程度不相关，因此表明近交主要是由于自交，而不是空间结构种群中近亲之间的交配。我们的结果表明，萱草种群在景观中的个体空间分布以及FSGS的模式和程度存在相当大的差异。这种差异总体上与这些种群内部生态过程中特定于演替阶段的差异一致。
