Integrative evidence reveals non-monophyly and chloroplast capture of Primula sect. Monocarpicae , with a new species from Yunnan, Southwest China

This is the authors' abstract. We don't add key points for this paper.

Primula sect. Monocarpicae is a morphologically distinct section endemic to the mountains of south-west China. Although its core species composition has remained taxonomically stable, the circumscription of the section and the placement of several contentious taxa have long remained unresolved. In this study, we integrated phylogenetic analyses of complete plastome sequences and nuclear ribosomal ITS data with morphological and geographic evidence to better understand the circumscription and phylogenetic relationships of sect. Monocarpicae, with particular attention to taxonomically contentious species and previously undescribed diversity. Our phylogenetic analyses reveal that sect. Monocarpicae is non-monophyletic and that its core species are resolved into two well-supported lineages, here designated the Cavaleriei Clade and the Malacoides Clade. The Cavaleriei Clade is characterized by an efarinose habit, orbicular to reniform leaves, and a base chromosome number of x = 12, whereas the Malacoides Clade is distinguished by farinose indumentum, ovate to oblong leaves, and a base chromosome number of x = 9. Geographically, these two clades occupy largely non-overlapping ranges across the mountains of south-west China. In addition, the cytonuclear discordance detected in P. epilithica is inferred to have resulted from chloroplast capture through reticulate hybridization with sympatric members of the Malacoides Clade. Finally, a new species of sect. Monocarpicae, Primula longmaensis sp. nov., is described from Yunnan, south-west China. It is morphologically distinguished by its unique oblanceolate mature leaves and exhibits a rare developmental transition known as heteroblasty. Our findings provide a phylogenetic foundation for the future taxonomic revision of sect. Monocarpicae and advance our understanding of Primula diversification in the mountains of south-west China.