Stamen traits significantly influence pollen presentation patterns and play a critical role in mating systems, floral evolution, and the diversification of angiosperms. Anthers within a flower can either develop freely or be united, resulting in three primary modes: separated anthers, synandry, and paired-united anthers. The impact of these anther modes on species diversification remains inadequately understood. In this study, we employed 14 plastid and nuclear ribosomal markers from 789 species to reconstruct the phylogenetic relationships of the Old World Didymocarpoideae, which are predominantly bee-pollinated. We then investigated the evolutionary patterns of anther modes and assessed their potential role in species diversification. Our findings indicate that the evolution of anther modes and associated floral traits exhibited significant trait conservatism. Paired-united anthers likely represent the ancestral form of Didymocarpoideae, characterized by four fertile stamens with exserted locations for the anthers. Notably, derived synandry was associated with relatively high rates of species diversification, particularly in the species-rich Cyrtandra, Primulina, and Streptocarpus, which could be due to enhanced pollination precision facilitated by aggregations of anthers and pollen grains. This study elucidates the evolutionary transitions of different anther modes while highlighting their influence on diversification rates within Didymocarpoideae.

Hainan Island harbours an extraordinary diversity of Gesneriaceae with 14 genera and 23 species, among which two species and one variety are recognized in the genus Oreocharis. These three Oreocharis taxa are all Hainan-endemics and show complex geographical distribution pattern with considerable morphological intermixtures. In this study, we combined DNA (nuclear ITS sequences and cpDNA trnL-trnF and ycf1b) to evaluate genetic delimitation for 12 Oreocharis populations from the island, together with morphological similarity analysis using 16 morphological traits. The results showed Hainan Oreocharis taxa was monophyly with relative low genetic diversity within populations, highly significant genetic differentiation among populations and a significant phylogeographical structure. The 12 populations formed three genetically distinct groups, roughly correspondent to the currently recognized two species and one unknown lineage. The PCA analyses of morphological traits indicate three distinctive groups, differing mainly in petal color and corolla shape and types. The roles of river isolation in the origin and distribution of these three lineages are discussed.