Institute of Landscape Ecology and Resource Management, Research Centre for BioSystems, Land Use and Nutrition (IFZ), Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany.
Ann Bot. 2012 Aug;110(3):585-93. doi: 10.1093/aob/mcs117. Epub 2012 Jun 22.
Ongoing and previous range expansions have a strong influence on population genetic structure of plants. In turn, genetic variation in the new range may affect the population dynamics and the expansion process. The annual Ceratocapnos claviculata (Papaveraceae) has expanded its Atlantic European range in recent decades towards the north and east. Patterns of genetic diversity were investigated across the native range to assess current population structure and phylogeographical patterns. A test was then made as to whether genetic diversity is reduced in the neophytic range and an attempt was made to identify source regions of the expansion.
Samples were taken from 55 populations in the native and 34 populations in the neophytic range (Sweden, north-east Germany). Using amplified fragment length polymorphism markers an analysis was made of genetic variation and population structure (Bayesian statistical modelling) and population differentiation was quantified. Pollen/ovule ratio was analysed as a proxy for the breeding system.
Genetic diversity at population level was very low (mean H(e) = 0·004) and two multilocus genotypes dominated large parts of the new range. Population differentiation was strong (F(ST) = 0·812). These results and a low pollen/ovule ratio are consistent with an autogamous breeding system. Genetic variation decreased from the native to the neophytic range. Within the native range, H(e) decreased towards the north-east, whereas population size increased. According to the Bayesian cluster analysis, the putative source regions of the neophytic range are situated in north-west Germany and adjacent regions.
Ceratocapnos claviculata shows a cline of genetic variation due to postglacial recolonization from putative Pleistocene refugia in south-west Europe. Nevertheless, the species has expanded successfully during the past 40 years to southern Sweden and north-east Germany where it occurs as an opportunistic neophyte. Recent expansion was mainly human-mediated by single long-distance diaspore transport and was facilitated by habitat modification.
植物的种间扩张和历史扩张对种群遗传结构有重要影响。而新分布区的遗传变异可能会影响种群动态和扩张过程。近年来，一年生罂粟科角茴香（Ceratocapnos claviculata）已从大西洋欧洲分布区向北部和东部扩展。本研究对该种的整个自然分布区进行了遗传多样性调查，以评估当前的种群结构和系统地理格局，并检验新分布区的遗传多样性是否降低，以及尝试确定扩张的起源区。
在自然分布区和新分布区（瑞典、德国东北部）共采集了 55 个和 34 个种群的样本。利用扩增片段长度多态性（AFLP）标记，分析了遗传变异和种群结构（贝叶斯统计建模），并量化了种群分化。通过分析花粉/胚珠比（P/O 比）来估计其繁育系统。
种群水平的遗传多样性非常低（平均 H(e) = 0·004），且有两个多态性位点基因型在新分布区的大部分地区占主导地位。种群分化较强（F(ST) = 0·812）。这些结果与低 P/O 比均表明该种为自交繁育系统。遗传多样性从自然分布区到新分布区逐渐降低。在自然分布区内，H(e)自西向东逐渐降低，而种群大小则逐渐增大。根据贝叶斯聚类分析，新分布区的潜在起源区位于德国西北部和相邻地区。
角茴香表现出沿冰川后再定殖方向的遗传变异梯度，这可能是由西南欧的更新世避难所造成的。尽管如此，该种在过去 40 年中仍成功扩张到瑞典南部和德国东北部，在这些地区成为机会主义的新生种。最近的扩张主要是由人类介导的长距离种子传播引起的，并得到了生境变化的促进。
