State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, 100093 Beijing, China; National Genebank, Institute of Crop Sciences (ICS), Chinese Academy of Agricultural Sciences (CAAS), Nan Dajie 12, Zhongguancun, Beijing 100081, China.
Botanic Institute of Barcelona (IBB, CSIC-ICUB), Passeig del Migdia s/n, 08038 Barcelona, Spain.
Mol Phylogenet Evol. 2018 Aug;125:62-77. doi: 10.1016/j.ympev.2018.03.003. Epub 2018 Mar 7.
According to the present taxonomical treatment, Paeonia subsect. Delavayanae consists of only two species (P. delavayi and P. ludlowii) endemic to the Himalayan-Hengduan Mountains. Although P. ludlowii can be distinguished from P. delavayi on the basis of a series of morphological characters, the species delimitation remains controversial because the more widespread one, P. delavayi, exhibits considerable morphological diversity. Both chloroplast DNA markers and nuclear microsatellites or simple sequence repeats (nSSR) are used herein to reveal genetic diversity and relationships of the two taxa included in this subsection, and ecological niche modeling (ENM) is employed to get insights into their paleodistribution. Our results show that genetic boundaries between the two currently recognized species are unclear, probably due to recent divergence. Paeonia ludlowii is budding from P. delavayi, probably by genetic isolation but also by shifting its niche to the harsher upland Tibetan conditions. Paeonia delavayi itself would be, however, under active speciation, showing significant genetic differentiation and morphological diversity. Whereas P. ludlowii would have endured the Pleistocene glacial periods by in situ persistence in local, small refugia, a 'dual' model seems to apply for P. delavayi (in situ persistence and retreat to refugia). The rarity of P. ludlowii and high evolutionary potential of P. delavayi imply high priority for in situ conservation of both taxa. The Himalayan-Hengduan Mountains are an ideal arena for differentiation within subsect. Delavayanae of Paeonia, by means of expansions/contractions/displacements, vertical migrations, and local survival/extinctions in response to the Neogene climate fluctuations and geological changes.
根据目前的分类处理，牡丹亚组 Delavayanae 仅由两种特有于喜马拉雅-横断山脉的物种组成（Paeonia delavayi 和 P. ludlowii）。尽管 P. ludlowii 可以基于一系列形态特征与 P. delavayi 区分开来，但物种界限仍然存在争议，因为分布更为广泛的 P. delavayi 表现出相当大的形态多样性。本文同时使用叶绿体 DNA 标记和核微卫星或简单序列重复（nSSR）来揭示该亚组中包含的两个类群的遗传多样性和关系，并采用生态位模型（ENM）来深入了解它们的古分布。我们的结果表明，这两个目前公认的物种之间的遗传边界不清楚，可能是由于最近的分化。Paeonia ludlowii 可能是由遗传隔离但也可能是通过将其生态位转移到更恶劣的高原藏区而从 P. delavayi 中萌发出来的。然而，P. delavayi 本身可能正在积极地进行物种形成，表现出显著的遗传分化和形态多样性。而 P. ludlowii 可能通过在当地小避难所中就地持续存在而在更新世冰期幸存下来，而对于 P. delavayi 来说，似乎适用“双重”模式（就地持续存在和撤退到避难所）。P. ludlowii 的稀有性和 P. delavayi 的高进化潜力意味着这两个类群的就地保护具有高度优先性。喜马拉雅-横断山脉是牡丹亚组 Delavayanae 内分化的理想场所，通过扩张/收缩/位移、垂直迁移以及对新近纪气候波动和地质变化的局部生存/灭绝来实现。
