Data from: Genetic differentiation and admixture between sibling allopolyploids in the Dactylorhiza majalis complex

Allopolyploidization often happens recurrently, but the evolutionary significance of its iterative nature is not yet fully understood. Of particular interest are the gene flow dynamics and the mechanisms that allow young sibling polyploids to remain distinct while sharing the same ploidy, heritage and overlapping distribution areas. By using eight highly variable nuclear microsatellites, newly reported here, we investigate the patterns of divergence and gene flow between 386 polyploid and 42 diploid individuals, representing the sibling allopolyploids Dactylorhiza majalis s.s. and D. traunsteineri s.l. and their parents at localities across Europe. We make use in our inference of the distinct distribution ranges of the polyploids, including areas in which they are sympatric (that is, the Alps) or allopatric (for example, Pyrenees with D. majalis only and Britain with D. traunsteineri only). Our results show a phylogeographic signal, but no clear genetic differentiation between the allopolyploids, despite the visible phenotypic divergence between them. The results indicate that gene flow between sibling Dactylorhiza allopolyploids is frequent in sympatry, with potential implications for the genetic patterns across their entire distribution range. Limited interploidal introgression is also evidenced, in particular between D. incarnata and D. traunsteineri. Altogether the allopolyploid genomes appear to be porous for introgression from related diploids and polyploids. We conclude that the observed phenotypic divergence between D. majalis and D. traunsteineri is maintained by strong divergent selection on specific genomic areas with strong penetrance, but which are short enough to remain undetected by genotyping dispersed neutral markers.异源多倍化（allopolyploidization）通常反复发生，但其迭代特性的进化意义尚未完全阐明。当前研究尤为关注两类问题：一是基因流动动态，二是使年幼的姊妹多倍体在拥有相同倍性、遗传背景与重叠分布区的前提下仍能保持分化的机制。本研究首次报道了8个高多态性核微卫星（nuclear microsatellites）标记，依托这些标记，我们对分布于欧洲各地的386个多倍体个体与42个二倍体个体展开了分析，这些样本涵盖姊妹异源多倍体狭义掌裂兰（Dactylorhiza majalis s.s.）、广义特拉恩斯坦掌裂兰（D. traunsteineri s.l.）及其二倍体亲本。我们利用多倍体的独特分布范围开展推断，其中既包括二者同域分布的区域（如阿尔卑斯山），也包括异域分布的区域：例如仅分布狭义掌裂兰的比利牛斯山，以及仅分布广义特拉恩斯坦掌裂兰的英国。研究结果显示出系统地理学（phylogeographic）信号，但尽管这两个异源多倍体存在显著的表型分化，二者之间并未出现明确的遗传分化。结果表明，姊妹掌裂兰异源多倍体之间的基因流动在同域分布区域中十分频繁，这可能对其整个分布范围内的遗传模式产生潜在影响。研究还证实存在有限的倍间渐渗（interploidal introgression）现象，尤其是在肉色掌裂兰（Dactylorhiza incarnata）与广义特拉恩斯坦掌裂兰之间。总而言之，异源多倍体基因组对于来自相关二倍体和多倍体的渐渗似乎具有多孔性。我们得出结论：狭义掌裂兰与广义特拉恩斯坦掌裂兰之间观测到的表型分化，是由特定基因组区域上的强歧化选择所维持的，这类选择具有较高的外显率，但所作用的基因组区域长度较短，以至于通过对分散的中性标记进行基因分型无法被检测到。