克隆的空间分布和大小对沼泽羊胡子草（Comarum palustre）实现的异交率的影响。
Influence of spatial distribution and size of clones on the realized outcrossing rate of the marsh cinquefoil (Comarum palustre).
机构信息
Earth and Life Institute-Research group Genetics, Reproduction, Populations, Université catholique de Louvain, Croix du Sud 2, Box L705 14, B-1348 Louvain-la-Neuve, Belgium.
出版信息
Ann Bot. 2014 Feb;113(3):477-87. doi: 10.1093/aob/mct280. Epub 2013 Nov 26.
BACKGROUND AND AIMS
Clonal growth is a common feature in flowering plants. As clone size increases, the selfing rate in self-compatible species is likely to increase due to more frequent geitono-pollination events (i.e. pollination among flowers within the same genet). This study investigated the breeding system of the marsh cinquefoil (Comarum palustre) and assessed spatial distribution of clones, clone size and architecture, and their effects on realized outcrossing rates. In addition, pollen dispersal was investigated in two patchy populations.
METHODS
The species' breeding system was investigated under controlled conditions through hand pollinations (self- vs. cross-pollination). Using microsatellite markers, an assessment was made of the realized outcrossing rates and the genetic diversity in four natural populations, the clonal structure in two populations within five 15 × 15 m sampling plots following 0.5 × 0.5 m grids, and the pollen dispersal through paternity assignment tests in those two populations.
KEY RESULTS
Comarum palustre is a self-compatible species but only presents a low rate of spontaneous self-pollination. The occurrence of inbreeding depression was not detected at the seed set stage (δ(SS) = 0.04). Clones were spatially clumped (A(C) = 0.60-0.80), with intermediate to no intermingling of the ramets (D(C) = 0.40-1.00). Genet size ranged from one to 171 ramets. Patchy populations had low outcrossing rates (t(m) = 0.33-0.46). Large clones showed lower outcrossing rates than small clones. Pollen dispersal mainly occurred within patches as only 1-7 % of the pollination events occurred between patches of >25 m separation. Seedling recruitment events were detected.
CONCLUSIONS
Genet size together with distances between patches, through increasing geitono-pollination events, appeared to be important factors influencing realized outcrossing rates. The study also revealed seed flow allowing seedling recruitment, which may contribute to increasing the number of new patches, and potentially further enhance gene flow within populations.
背景与目的
克隆生长是开花植物的一个共同特征。随着克隆体的增大，自交亲和物种的自交率可能会增加，因为基因间的异交授粉事件（即同一遗传体中花朵之间的授粉）更为频繁。本研究调查了沼泽五福草（Comarum palustre）的繁殖系统，并评估了克隆体的空间分布、克隆大小和结构，以及它们对实际异交率的影响。此外，还在两个斑块状种群中调查了花粉传播。
方法
通过人工授粉（自交与异交）在控制条件下研究了该物种的繁殖系统。使用微卫星标记，评估了四个自然种群的实际异交率和遗传多样性，在两个种群的五个 15×15 m 采样斑块中，按照 0.5×0.5 m 网格进行了克隆结构的研究，以及在这两个种群中通过亲子关系赋值试验进行了花粉传播的研究。
主要结果
沼泽五福草是自交亲和物种，但只表现出较低的自发自交率。在种子结实阶段未检测到近交衰退（δ（SS）=0.04）。克隆体在空间上呈聚集分布（A（C）=0.60-0.80），分株间的混杂程度中等至无（D（C）=0.40-1.00）。基因大小范围从一个到 171 个分株。斑块状种群的异交率较低（t（m）=0.33-0.46）。大克隆体的异交率低于小克隆体。花粉传播主要发生在斑块内，只有 1-7%的授粉事件发生在相隔>25 m 的斑块之间。检测到了幼苗繁殖事件。
结论
基因大小以及斑块之间的距离，通过增加基因间的异交授粉事件，似乎是影响实际异交率的重要因素。该研究还揭示了允许幼苗繁殖的种子流，这可能有助于增加新斑块的数量，并可能进一步增强种群内的基因流。
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