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(Ponci...

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.