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Asymmetric contributions of seed and pollen to gene dispersal in the marsh orchid Dactylorhiza umbrosa in Asia Minor
Molecular Ecology ( IF 4.9 ) Pub Date : 2021-02-15 , DOI: 10.1111/mec.15848
Mikael Hedrén 1 , Sven Birkedal 2 , Hugo de Boer 3, 4, 5 , Abdolbaset Ghorbani 4 , Barbara Gravendeel 5 , Sven Hansson 6 , Åke Svensson 7 , Shahin Zarre 8
Affiliation  

Orchids differ from other plants in their extremely small and partly air‐filled seeds that can be transported long distances by wind. Seed dispersal in orchids is expected to contribute strongly to overall gene flow, and orchids generally express low levels of genetic differentiation between populations and low pollen to seed flow ratios. However, studies in orchids distributed in northern Europe have often found a poor geographic structuring of genetic variation. Here, we studied geographic differentiation in the marsh orchid Dactylorhiza umbrosa, which is widely distributed in upland regions from Asia Minor to Central Asia. These areas were less affected by Pleistocene ice ages than northern Europe and the orchid should have been able to survive the last ice age in local refugia. In the plastid genome, which is dispersed by seeds, populations at close distance were clearly divergent, but the differentiation still increased with geographic distance, and a significant phylogeographic structure had developed. In the nuclear genome, which is dispersed by both seeds and pollen, populations showed an even stronger correlation between genetic and geographic distance, but average levels of differentiation were lower than in the plastid genome, and no phylogeographic structure was evident. Combining plastid and nuclear data, we found that the ratio of pollen to seed dispersal (mp/ms) decreases with physical distance. Comparison with orchids that grow in parts of Europe that were glaciated during the last ice suggests that a balanced structure of genetic diversity develops only slowly in many terrestrial orchids, despite efficient seed dispersal.

中文翻译:

种子和花粉对亚洲小沼泽兰花Dactylorhiza umbrosa基因分散的不对称贡献

兰花与其他植物的不同之处在于,它们的种子极小且部分充满空气,可以通过风将其长距离运输。种子在兰花中的传播有望对总体基因流产生重要影响,兰花通常在种群之间表现出较低的遗传分化水平,而花粉与种子的流率却很低。然而,对分布在北欧的兰花的研究通常发现遗传变异的地理结构不佳。在这里,我们研究了沼泽兰花Dactylorhiza umbrosa中的地理差异广泛分布在从小亚细亚到中亚的高地地区。与北欧相比,这些地区受更新世冰期的影响较小,兰花应该能够在当地避难所的最后一次冰期中幸存下来。在由种子分散的质体基因组中,近距离的种群明显有差异,但分化程度仍随地理距离而增加,并且已形成重要的系统地理结构。在由种子和花粉分散的核基因组中,种群显示出遗传距离与地理距离之间甚至更强的相关性,但平均分化水平低于质体基因组,并且没有明显的谱系结构。结合质体和核数据,我们发现花粉与种子扩散的比例(mp / ms)随物理距离而减小。与欧洲部分地区在最后一次冰期中冰川化的兰花进行的比较表明,尽管种子有效分散,但许多陆地兰花的遗传多样性平衡结构仅缓慢发展。
更新日期:2021-04-12
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