Vincetoxicum and Tylophora (Apocynaceae: Asclepiadoideae: Asclepiadeae)—two sides of the same medal: Independent shifts from tropical to temperate habitats

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Abstract:

A revised phylogeny of Tylophorinae, based on 77 species of all genera presently attributed to the subtribe (Biondia, Blyttia, Diplostigma, Goydera, Pentatropis, Pleurostelma, Rhyncharrhena, Tylophora, Vincetoxicum) is presented. Five chloro plast markers (trnT-L, trnL-F, and psbA-trnH intergenic spacers as well as the trnL and trnG introns) and two nuclear markers (ITS, ETS) were used, totalling in 3809 base pairs. Tylophorinae are strongly monophyletic and consist of several well-defined clades. Backbone resolution between these clades is low, indicating a rapid early radiation. Pentatropis is sister to all remaining taxa, albeit with weak support; all other taxa form one big clade not corresponding to previous generic delimitations. Therefore, all genera except for Pentatropis are subsumed under Vincetoxicum. The early branching clades of Vincetoxicum s.l. all grow in Africa, where the group originated ca. 18 Ma ago, correlating with the closure of the Tethys Ocean. The first round of dif ferentiation took place between 12 and 15 Ma ago, resulting in Tylophorinae being distributed over almost all of their present range except for South Africa, Arabia and Europe. Two unrelated lineages of temperate, mostly erect plants hitherto named “Vincetoxicum” have arisen from more tropical lineages, hitherto named “Tylophora”. One clade of African species is nested inside the Australasian assemblage; this clade contains exclusively polyploid species and its re-immigration to Africa took place in the Messinian, at ca. 6.8 Ma. The European Vincetoxicum species split from erect steppe plants of temperate Asia at ca. 4.5 Ma, coinciding with the uplift of the Tibetan plateau. This group contains two species that are presently aggressively spreading in North America after chance introductions.

Keywords: CHROMOSOME NUMBERS; HAPLOTYPE ANALYSIS; MOLECULAR DATING; MOLECULAR SYSTEMATICS; PENTATROPIS; PHYLOGENY; POLYPLOIDY; S-DIVA

Document Type: Research Article

Affiliations: 1: Department of Plant Systematics, University of Bayreuth, 95440 Bayreuth, Germany;, Email: sigrid.liede@uni-bayreuth.de 2: Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, 510650 Guangzhou, P.R. China 3: Department of Plant Systematics, University of Bayreuth, 95440 Bayreuth, Germany 4: Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany

Publication date: August 14, 2012

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