title: Phylogeny and historical biogeography of Isodon (Lamiaceae): rapid radiation in south-west China and Miocene overland dispersal into Africa.
abstract: Rapid organismal radiations occurring on the Qinghai-Tibetan Plateau (QTP) and the mechanisms underlying Asia-Africa intercontinental disjunctions have both attracted much attention from evolutionary biologists. Here we use the genus Isodon (Lamiaceae), a primarily East Asian lineage with disjunct species in central and southern Africa, as a case study to shed light upon these processes. The molecular phylogeny and biogeographic history of Isodon were reconstructed using sequences of three plastid markers, the nuclear ribosomal internal transcribed spacer (nrITS), and a low-copy nuclear gene (LEAFY intron II). The evolution of chromosome numbers in this genus was also investigated using probabilistic models. Our results support a monophyletic Isodon that includes the two disjunct African species, both of which likely formed through allopolyploidy. An overland migration from Asia to Africa through Arabia during the early Miocene is proposed as the most likely explanation for the present disjunct distribution of Isodon. The opening of the Red Sea in the middle Miocene may appear to have had a major role in disrupting floristic exchange between Asia and Africa. In addition, a rapid radiation of Isodon was suggested to occur in the late Miocene. It corresponds with one of the major uplifts of the QTP and subsequent aridification events. Our results support the hypothesis that geological and climatic events play important roles in driving biological diversification of organisms distributed in the QTP area.
authors.affiliation: Laboratory of Plant Phylogenetics and Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, Yunnan 650223, PR China; Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Yunnan 666303, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
authors.forename: Xiang-Qin
authors.initials: XQ
authors.lastname: Yu
authors.affiliation: Division of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Maki
authors.affiliation: Museum of Natural History, Department of Biology, University of Florida, USA.
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Drew
authors.affiliation: The Herbarium, Royal Botanic Gardens, Kew, Richmond TW9 3AB, UK.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Paton
authors.affiliation: Herbarium (KUN), Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650204, PR China.
authors.forename: Hsi-Wen
authors.initials: HW
authors.lastname: Li
authors.affiliation: Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Yunnan 666303, PR China.
authors.forename: Jian-Li
authors.initials: JL
authors.lastname: Zhao
authors.affiliation: Centre for Evolutionary Biology and Biodiversity & Sprigg Geobiology Centre, School of Earth and Environmental Sciences, Benham Bldg DX 650 312, The University of Adelaide, SA 5005, Australia.
authors.forename: John G
authors.initials: JG
authors.lastname: Conran
authors.affiliation: Laboratory of Plant Phylogenetics and Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming, Yunnan 650223, PR China; Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Yunnan 666303, PR China. Electronic address: jieli@xtbg.ac.cn.
authors.forename: Jie
authors.initials: J
authors.lastname: Li
mesh_terms: D000349:Africa; D002681:China; D032461:Chromosomes, Plant; D037602:Isodon / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D058974:Phylogeography; D017422:Sequence Analysis, DNA
keywords: Hengduan Mountains region; Intercontinental disjunction; Isodon; Overland dispersal; Qinghai–Tibetan Plateau; Rapid radiation