State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093 China; Graduate School, Chinese Academy of Sciences, Beijing 100039 China; and Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824 USA.
Am J Bot. 2007 Mar;94(3):400-8. doi: 10.3732/ajb.94.3.400.
There is growing evidence that hybridization not only by means of allopolyploidy but also at the homoploidy level was a major driving force of plant diversification. While allopolyploidy is known to be a common mode of speciation in Paeonia (Paeoniaceae), hybrid speciation at the diploid level needs further evaluation. Paeonia anomala was previously considered to be an interspecific hybrid but with an unknown ploidy level. In this study P. anomala is identified as a diploid (2n = 10). With increased sampling of populations and molecular markers, we showed that P. anomala is a homoploid hybrid that originated from a cross between P. veitchii and P. lactiflora. Five populations of P. anomala were sequenced for the following molecular markers: the matK gene and two intergenic spacers, psbA-trnH and rps16-trnQ, of the chloroplast genome; the internal transcribed spacers (ITS) of nuclear ribosomal DNA; and three low-copy nuclear genes, Adh1, Adh2, and Gpat. The populations of P. anomala were grouped together with P. veitchii on the ITS and Gpat phylogenies but with P. lactiflora on the chloroplast phylogeny. Sequence polymorphism was found at the Adh1 and Adh2 loci within individuals of P. anomala. These polymorphic sequences were grouped with P. veitchii and P. lactiflora, respectively. Phenetic analysis indicated that P. anomala is morphologically similar to P. veitchii. Phenotypic evolution resulting from the combination of two diverged genomes might have occurred primarily at the physiological level and allowed P. anomala to adapt to geographic regions different from those of its parents.
越来越多的证据表明，杂交不仅仅是通过异源多倍体，而且在同源多倍体水平上，也是植物多样化的主要驱动力。虽然异源多倍体是牡丹属（芍药科）物种形成的常见模式，但在二倍体水平上的杂种物种形成需要进一步评估。牡丹芍药先前被认为是种间杂种，但倍性水平未知。在这项研究中，牡丹芍药被鉴定为二倍体（2n=10）。通过增加对种群和分子标记的采样，我们表明牡丹芍药是同源多倍体杂种，起源于牡丹芍药和牡丹芍药的杂交。对五个牡丹芍药种群进行了以下分子标记的测序：叶绿体基因组的 matK 基因和两个基因间间隔区 psbA-trnH 和 rps16-trnQ；核核糖体 DNA 的内部转录间隔区（ITS）；以及三个低拷贝核基因 Adh1、Adh2 和 Gpat。牡丹芍药种群在 ITS 和 Gpat 系统发育树上与牡丹芍药聚在一起，但在叶绿体系统发育树上与牡丹芍药聚在一起。在牡丹芍药个体的 Adh1 和 Adh2 基因座发现了序列多态性。这些多态性序列分别与牡丹芍药和牡丹芍药聚在一起。表型分析表明，牡丹芍药在形态上与牡丹芍药相似。来自两个分化基因组的组合引起的表型进化可能主要发生在生理水平上，使牡丹芍药能够适应与其亲本不同的地理区域。
