Taxonomy of Vincetoxicum s.str. (Asclepiadoideae, Apocynaceae) from southern Asia including three new species and resurrected names

Molecular phylogeny of Vincetoxicum (Apocynaceae, Asclepiadoideae) from Thailand and integrative taxonomy corroborating a new cryptic species within Vincetoxicum kerrii

An updated phylogeny of the genus Vincetoxicum s.l. based on DNA sequences of the nuclear internal transcribed spacer (ITS) region and three plastid markers is presented. In total, 21 accessions newly sequenced from Thailand were added to the dataset of the homologous sequences of 75 other Vincetoxicum taxa downloaded from GenBank. In our analysis, the relationships between the well-supported clades largely correspond to those revealed in previous studies. With some exceptions, the phylogenetic positions of the Thai taxa in relation to other conspecifics and congeners generally reflect the geographic distributions of taxa. Moreover, recent extensive sampling throughout Thailand and in-depth investigation have revealed V. kerrii, a slender twiner widespread from South China to Indo-China, to be a species complex. A combination of molecular, morphological, anatomical, ultrastructural and ecological evidence allowed us to reveal a new cryptic species hidden within V. kerrii, described here under the name V. simplex. A comprehensive description, illustrations, photographs, and comparison with the morphologically similar species are provided. Although V. simplex and V. kerrii s.s. resemble one another in various aspects of vegetative and reproductive structures, the latter is phylogenetically closely related to V. irrawadense, which is much less similar morphologically to both V. simplex and V. kerrii s.s. than the latter two are to each other. In addition to the new cryptic species recognized in the present study, a new record for Thailand, V. microstachys, is also reported.

The complete plastid genome of Vincetoxicum junzifengense B.J. Ye and S.P. Chen (Apocynaceae)

Vincetoxicum junzifengense B.J. Ye and S.P. Chen 2022 is a newly described species which belongs to the genus Vincetoxicum in the family Apocynaceae. The complete plastid genome of Vincetoxicum junzifengense B.J. Ye and S.P. Chen 2022 was determined and analyzed in this study. The total chloroplast genome was 159,666 bp in length, consisting of a large single-copy region of 90,565 bp, a small single-copy region of 19,691 bp, and two inverted repeat regions of 24,705 bp. The genome contained 131 genes, including 85 protein-coding genes, 37 transfer RNA genes, and eight ribosomal RNA genes. Phylogenetic analysis indicated that V. junzifengense is sister to V. versicolor.