Institute for Conservation Biology and School of Biological Sciences, University of Wollongong, Wollongong, New South Wales 2522, Australia.
Ann Bot. 2011 Jul;108(1):185-95. doi: 10.1093/aob/mcr100. Epub 2011 May 5.
Plants show patterns of spatial genetic differentiation reflecting gene flow mediated by pollen and seed dispersal and genotype × environment interactions. If patterns of genetic structure are determined largely by gene flow then they may be useful in predicting the likelihood of inbreeding or outbreeding depression but should be less useful if there is strong site-specific selection. For many Australian plants little is known about either their population genetics or the effects on mating systems of variation in pollen transfer distances. Experimental pollinations were used to compare the reproductive success of bird-adapted Grevillea mucronulata plants mated with individuals from a range of spatial scales. A hierarchical survey of microsatellite DNA variation was also conducted to describe the scale of population differentiation for neutral markers.
The effects of four pollen treatments on reproductive performance were compared. These treatments were characterized by transfer of pollen from (a) neighbouring adults; (b) an adjacent cluster of adults (30-50 m distant); (c) a distant cluster (>5 km distant); and (d) open pollination. Sets of 17·9 ± 3·3 leaves from each of 15 clusters of plants were genotyped and spatial autocorrelation and F statistics were used to describe patterns of genetic structure.
Grevillea mucronulata displayed evidence of both inbreeding and outbreeding depression, with 'intermediate' pollen producing consistently superior outcomes for most aspects of fitness including seed set, seed size, germination and seedling growth. Significant genotypic structuring was detected within clusters (spatial autocorrelation) and among adjacent clusters and clusters separated by >5 km distance (F(ST) = 0·07 and 0·10).
The superior outcome of intermediate pollen transfer and genetic differentiation of adjacent clusters suggests that G. mucronulata selection disfavours matings among closely and distantly related neighbours. Moreover, the performance of open-pollinated seedlings was poor, implying that current mating patterns are suboptimal.
植物表现出空间遗传分化的模式，反映了花粉和种子扩散介导的基因流以及基因型与环境相互作用。如果遗传结构模式主要由基因流决定，那么它们可能有助于预测近交或远交衰退的可能性，但如果存在强烈的特定地点选择，则它们的作用可能较小。对于许多澳大利亚植物，其种群遗传学或花粉转移距离变化对交配系统的影响知之甚少。实验授粉用于比较适应鸟类的 Grevillea mucronulata 植物与来自一系列空间尺度的个体交配的繁殖成功率。还进行了微卫星 DNA 变异的层次调查，以描述中性标记的种群分化规模。
比较了四种花粉处理对繁殖性能的影响。这些处理的特征是花粉从（a）邻近的成年个体；（b）相距 30-50 米的相邻成簇个体；（c）相距较远的成簇个体（>5 公里远）；和（d）开放授粉。从每组 15 个植物簇中的每一个中收集 17.9±3.3 片叶子进行基因型分析，并使用空间自相关和 F 统计量描述遗传结构模式。
Grevillea mucronulata 表现出近交和远交衰退的证据，“中间”花粉在包括种子结实率、种子大小、发芽和幼苗生长在内的大多数适应度方面始终产生更好的结果。在簇内（空间自相关）和相邻簇之间以及相隔>5 公里的簇之间检测到显著的基因型结构（F(ST)分别为 0.07 和 0.10）。
中间花粉转移的优越结果和相邻簇之间的遗传分化表明，G. mucronulata 的选择不利于紧密和遥远相关邻居之间的交配。此外，开放授粉幼苗的表现不佳，这意味着当前的交配模式不是最佳的。
