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| a, b Sarcolobus busbanianus A.Kidyoo & Kidyoo, c, d S. flavus A.Kidyoo & Kidyoo, in M. Kidyoo, A. Kidyoo et McKey. 2024. Photographs by A. Kidyoo |
Abstract
The present study assesses the phylogenetic position of certain Thai members of Gymnema, Gymnemopsis, and Sarcolobus in relation to other known Marsdenieae species. Fifteen accessions newly sequenced from Thailand were added to the dataset of the homologous sequences of 125 accessions of Marsdenieae downloaded from GenBank. In our molecular phylogeny, almost all the delimited major clades and their relationships are largely congruent with those revealed in previous studies. The monophyly of Gymnema (including the former Jasminanthes species) and that of Sarcolobus, as presently circumscribed, are confirmed. The new accessions of these two genera from Thailand are well grouped with the members of their respective genera. Our analyses provide the first molecular evidence for recognition of Gymnemopsis, a small Asian genus that has never been included in the previous phylogenetic studies, as a distinct genus. All elements of Gymnemopsis are retrieved as a well-supported monophyletic group that is strongly supported as sister to Lygisma, another small Asian genus that most closely resembles it in growth habit, color of latex, indumentum on plant parts, corona structure and follicle traits. Combined molecular phylogenetic, morphological and ecological data also support recognition of two new Sarcolobus species from Thailand, Sarcolobus busbanianus sp. nov. and S. flavus sp. nov. Similarities and differences between these new species and their close relative, S. carinatus, are discussed. In addition, this study also reveals the first record for Thailand of Gymnema lacei. Keys to the species of Gymnemopsis (for all members of the genus), Gymnema and Sarcolobus (for Thai members of these genera) are provided.
Keywords: CpDNA, ITS, Mainland Southeast Asia, Marsdenia, Molecular phylogeny, Morphological taxonomy
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| Comparison of inflorescence (a, c) and floral morphology (b, d, e, f). a, b Sarcolobus busbanianus sp. nov. c, d S. flavus sp. nov. e S. carinatus f S. globosus. Photographs by A. Kidyoo |
Sarcolobus busbanianus A.Kidyoo & Kidyoo, sp. nov.
Etymology This species was named in honour of Assoc. Prof. Busban Na Songkhla, a senior instructor in the Department of Botany, Faculty of Science, Chulalongkorn University, who has made important contributions to plant taxonomic knowledge in Thailand.
Sarcolobus flavus A.Kidyoo & Kidyoo, sp. nov.
Etymology The specific epithet ‘flavus’ refers to the bright yellow color of its flowers.
Manit Kidyoo, Aroonrat Kidyoo and Doyle McKey. 2024. Phylogenetic Positions of Thai Members of Gymnema, Gymnemopsis and Sarcolobus (Apocynaceae, Asclepiadoideae, Marsdenieae), and Two New Sarcolobus Species uncovered by Morpho-molecular Evidence. Journal of Plant Research. DOI: doi.org/10.1007/s10265-024-01562-z
