利用DNA片段测序方法探究枳属和富民枳的分类地位

富民枳(Poncirus polyandra)属于芸香科(Rutaceae)枳属(Poncirus Raf.)。自发表以来,分类地位一直备受争议,其中在Flora of China中认为富民枳为柑橘杂交种(Poncirus polyandra),把枳属归并于柑橘属(Citrus)。该研究选取枳属的富民枳、枳(Poncirus trifoliata)及柑橘属下8个种共10个种47个个体作为研究材料,以九里香(Murraya exotica)为外类群,利用3个叶绿体片段(trn L-trn F、trn S-trn G、rbc L)、ITS片段和1个单拷贝核基因(Chr 5)数据构建系统发育树,探究枳属和富民枳的分类地位。结果表明:基于3个叶绿体片段数据构建的最大似然树(ML)和贝叶斯树(BI)的拓扑结构基本一致,10个物种聚为两大分支,即柑橘属的8个物种聚为一大分支,富民枳和枳聚为另一大分支。其中,富民枳所有个体聚为一小单系分支,枳的所有个体聚为一小单系分支,支持枳属和富民枳独立存在。2个核DNA片段数据结果显示,枳属的两个种与柑橘属的8个物种聚在一个大分支里,无法确立枳属的单系地位,但富民枳的9个个体聚在一起,暗示富民枳在遗传上是一个独立的类群。综上研究认为,无论是叶绿体DNA数据还是核DNA数据均支持富民枳是一个独立的物种,但核DNA数据不支持枳属成立。

Phylogenetic position of Poncirus and Poncirus polyandra by DNA sequencing

Poncirus polyandra belongs to the genus Poncirus Raf. of Rutaceae. Since it was published, its taxonomic status has always been controversial. In Flora of China, P. polyandra was regarded as a Citrus hybrid(Poncirus polyandra), and the genus Poncirus was included in the genus Citrus. In this study, we used three chloroplast DNA fragments(trnL-trnF, trnS-trnG, rbcL), ITS and one single copy nuclear genes(Chr5)to construct phylogenetic trees to explore the taxonomic status of the genus Poncirus and P. polyandra. We sampled a total of 47 individuals from ten species, including P. polyandra and P. trifoliata of the genus Poncirus as well as eight other species of the genus Citrus by using Murraya exotica was used as the outgroup. The results were as follows: The maximum likelihood trees(ML)and Bayesian inference trees(BI)constructed by all data were basically identical in topological structure. The cpDNA results showed that all species were clustered into two clades: eight species of Citrus were clustered into one major clade, and P. polyandra and P. trifoliata were clustered into another major clade. Meanwhile, all individuals of P. polyandra and P. trifoliata were grouped into a monophyletic subclade respectively, supporting the independence of Poncirus and P. polyandra could exist independently; However, the results of two nuclear DNA fragments showed that two species of Poncirus and the eight species of Citrus clustered into a large clade, indicating that the genus Poncirus cannot be recognized independently. Moreover, nine individuals of P. polyandra were monophyletic, suggesting that P. polyandra was a genetically independent lineage. In summary, both chloroplast DNA data and nuclear DNA data supported that P. polyandra was an independent taxa, but nuclear DNA data from our study did not support the independence of Poncirus.