Euphorbia Section Hainanensis (Euphorbiaceae), a New Section Endemic to the Hainan Island of China From Biogeographical, Karyological, and Phenotypical Evidence

• Published in: Frontiers in plant science Vol. 9; p. 660
• Main Authors: Tian, Xinmin, Wang, Qiuyan, Zhou, Yongfeng
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 18.05.2018
• Subjects: biogeography; endangered species; limestone mountains; long distance dispersal; phylogeny; Plant Science; endangered species; phylogeny; biogeography; limestone mountains; long distance dispersal
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2018.00660

is an endangered species endemic to the tropical Hainan Island in southern China and of historical importance for Chinese medicine. It is currently the only unplaced species of the genus (Euphorbiaceae) due to its isolated island distribution and debated placement by a previous molecular phylogenetic study. We sequenced nuclear ITS and chloroplast and for newly collected accessions of and additional species found in Hainan, and analyzed the sequences in the context of the entire genus together with published data. All gene regions highly supported that occupied an isolated phylogenetic position, showing no close affinity with any known sections suggesting it was a new section. ITS placed sister to sect. (subgenus ) from Brazil with an estimated divergence time of 9.3-30.6 Mya while the chloroplast markers placed at a position sister to the entire New World clade of subgenus . In addition, our karyological results suggested a close affinity between and the New World species of subg. , with which shared the same chromosome number 2n = 28 and basic chromosome number x = 7. Phenotypically, is unique with no close resemblance to other species in subg. . Based on its isolated biogeographical, karyological, and phenotypical position, we propose a new section . subgenus section that might origin from long distance dispersal events because collective evidences showed a close affinity between the species from the Old World with those from the New World.