Plastomes of limestone karst gesneriad genera Petrocodon and Primulina, and the comparative plastid phylogenomics of Gesneriaceae

Complete chloroplast genome of Petrocosmea qinlingensis (Gesneriaceae), a protected wild plant in the Qinling mountains

Petrocosmea qinlingensis is a protected wild plant endemic in China, inhabiting low-light limestone cliffs but the complete chloroplast genome has not been reported. In this study, we first sequenced and assembled the complete chloroplast genome of P. qinlingensis. The total size of this genome was 153,865 bp, including a large single-copy (LSC) region (84,737 bp), a small single-copy (SSC) region (18,244 bp), and two inverted repeats (IRs) regions (25,442 bp). This genome encoded 111 uniquegenes, consisted of 77 protein-coding genes, four ribosomal RNA genes, and 30 transfer RNA genes. Phylogenomic analysis based on the chloroplast protein-coding genes and showed that the genus Petrocosmea was the closest relative to Raphiocarpus. Our results will support further phylogeographic, population genetic studies of this species.

Primulinapingnanensis, a new species of Gesneriaceae from Guangxi, China

A new species of Primulina, P.pingnanensis, from the Guangxi Zhuangzu Autonomous Region, China, is described and illustrated here. It is morphologically similar to P.orthandra but has significant differences in the bracts, corolla tube and lobes shape, as well as in the indumentum of the outer surface of the corolla, the filaments, the staminodes and the anthers. Colorful photographs and essential information of this new taxon are also provided, including detailed taxonomic description, distribution, habitat, the comparison table, and the IUCN conservation status. We also discuss a validation of new combination P.crassifolia and Chiritacrassifolia.

Plastome evolution and phylogenomics of Trichosporeae (Gesneriaceae) with its morphological characters appraisal

Trichosporeae is the largest and most taxonomically difficult tribe of Gesneriaceae due to its diverse morphology. Previous studies have not clarified the phylogenetic relationships within this tribe on several DNA markers, including the generic relationships within subtribes. Recently, plastid phylogenomics have been successfully employed to resolve the phylogenetic relationships at different taxonomic levels. In this study, plastid phylogenomics were used to explore the relationships within Trichosporeae. Eleven plastomes of Hemiboea were newly reported. Comparative analyses, phylogeny and morphological character evolution within Trichosporeae were conducted on 79 species representing seven subtribes. The Hemiboea plastomes range from 152,742 bp to 153,695 bp in length. Within Trichosporeae, the sampled plastomes range from 152,196 bp to 156,614 bp and GC content from 37.2% to 37.8%. A total of 121-133 genes were annotated in each species, including 80-91 protein-coding genes, 34-37 tRNA genes, and 8 rRNA genes. The contraction and expansion of IR borders were not detected, and gene rearrangements and inversions did not occur. The 13 hypervariable regions were proposed as the potential molecular markers for species identification. A total of 24,299 SNPs and 3,378 indels were inferred, and most of the SNPs were functionally missense and silent variations. There were 1968 SSRs, 2055 tandem repeats and 2802 dispersed repeats. The RSCU and ENC values indicated that the codon usage pattern was conserved in Trichosporeae. Both the phylogenetic frameworks based on the whole plastome and 80 CDSs were basically concordant. The sister relationships between Loxocarpinae and Didymocarpinae were confirmed, and Oreocharis was a sister group of Hemiboea with high support. The morphological characters showed a complex evolutionary pattern of Trichosporeae. Our findings may contribute to future research on genetic diversity, morphological evolutionary patterns, and conservation of the tribe Trichosporeae.

Langbiangia, a new genus of Gesneriaceae endemic to Langbiang Plateau, southern Vietnam and a taxonomic endeavor to achieve key targets of the post-2020 global biodiversity framework

Situated in the southern end of the Annamite Mountain Range, Langbiang Plateau is a major biodiversity hotspot of southern Vietnam known for high species diversity and endemicity. To achieve effective conservation, parts of the plateau were designated as the Langbiang Biosphere Reserve, an UNESCO World Network aiming to improve relationships between inhabitants and their environments. Amongst the rich endemic flora of the plateau are three gesneriads ascribed to Primulina, a calciphilous genus with high species diversity in the vast limestone karsts stretching from southern China to northern Vietnam. However, a recent phylogenetic study questioned the generic placement of the Langbiang Primulina, corroborating with observations on the geographical distribution, habitat preference, and phyllotaxy of the three species. Based on phylogenetic analyses of nuclear ITS and plastid trnL-F DNA sequences of a comprehensive sampling covering nearly all genera of the Old World Gesneriaceae, we demonstrate that the three Langbiang Primulina species form a fully supported clade distantly related to other Primulina. As this clade is biogeographically, ecologically, morphologically, and phylogenetically distinct worthy of generic recognition, we propose to name it Langbiangia gen. nov. to highlight the rich and unique biodiversity of the Langbiang Plateau. By means of this taxonomic endeavor, we are hoping to raise the conservation awareness of this biodiversity heritage of southern Vietnam and promote the importance of Langbiang Biosphere Reserve that is crucial for achieving action-oriented global targets of the post-2020 global biodiversity framework (GBF) of the UN Convention on Biological Diversity (CBD)-effective conservation and management of at least 30% of biodiverse terrestrial, inland water, and costal and marine areas by 2030-that has been agreed at the COP15 in Montréal in December 2022.