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| Vincetoxicum sangyojarniae A.Kidyoo, in A. Kidyoo et M. Kidyoo, 2023. |
Abstract
An unknown Vincetoxicum species has recently been discovered in eastern Thailand. It is a twiner that resembles in its morphology Vincetoxicum flexuosum s.l., a variable taxon widely occurring from tropical Asia to Australia. Morphological examination showed that despite similarities in growth habit, leaf shape, gross appearance of inflorescence structure and flower colour, these two elements exhibit substantial differences in both vegetative and floral characters that clearly distinguish one from the other, particularly shape of the flower bud and indumentum on the corolla lobes. In addition, we also evaluated phylogenetic relationships based on DNA sequence data for ITS, trnT-L, trnL and trnL-F markers of this new Vincetoxicum sp. with congeners (including, inter alia, new sequences of the two varieties recognized in Thailand of V. flexuosum s.l., i.e. var. flexuosum and var. tenue). The analyses demonstrated that the new Vincetoxicum sp. is not closely related to the taxa recognized in V. flexuosum s.l. Instead, it was retrieved as sister to a clade containing the African taxa, Vincetoxicum caffrum, Vincetoxicum lycioides and Vincetoxicum fleckii. Therefore, integrated analyses of morphology and molecular phylogeny revealed the new Vincetoxicum sp. to be a well-defined species clearly distinct from V. flexuosum s.l., as well as from all other known congeners. The morphological similarity between the new Vincetoxicum sp. and V. flexuosum s.l. likely resulted from convergence, leading to various taxonomic complications. We here describe it as a new species, Vincetoxicum sangyojarniae, sp. nov., and provide a detailed description, illustration and photographs. Moreover, as phylogenetic relationships revealed that V. flexuosum s.l. is not monophyletic in its actual circumscription, a taxonomic reconsideration of this taxon is suggested.
Keywords: Convergence, Phylogeny, The Vincetoxicum flexuosum complex, Tylophora, Tylophorinae
Vincetoxicum sangyojarniae A.Kidyoo, sp. nov.
—TYPE: Thailand, Surin Province,
Muang district, Rajamangala University of Technology Isan Surin Campus, ....
Etymology: The specific epithet ‘sangyojarniae’ is given in honour of Asst. Prof. Pacharaporn Sangyojarn, the senior botanist of the Faculty of Agriculture and Technology, Rajamangala University of Technology Isan, who first discovered and drew our attention to the plant.
Aroonrat Kidyoo and Manit Kidyoo. 2023. Molecular Phylogenetic and Morphological Analyses support Recognition of A New Species of Vincetoxicum (Apocynaceae, Asclepiadoideae) from eastern Thailand. Plant Systematics and Evolution. 309, 27. DOI: doi.org/10.1007/s00606-023-01866-y
