Similar in appearance but distinct in nature: Recent divergence of Salvia honania and S. meiliensis

Accurate species delimitation is often challenging in cases of recent rapid radiations, where morphological similarities can lead to an underestimation of species diversity. By not recognizing taxonomic diversity, taxa that are economically or ecologically valuable may be overlooked. Salvia honania and S. meiliensis are morphologically quite similar and geographically restricted to the Dabie Mountains in central China. They provide an ideal system for exploring speciation and diversification within S. sect. Drymosphace , a group with noteworthy medicinal value. Previous molecular phylogenetic studies have provided insufficient evidence to clarify the taxonomic boundaries between these two taxa. Here, we employ an integrative taxonomic approach, combining population genetics, phylogeography, and morphology, to define the taxonomic status of the two species. A total of 211 individuals from 16 populations were analyzed across their entire geographical distributions. Significant genetic differentiation was observed, with clear interspecific divergence in genetic diversity, genetic structure, and population dynamics. Phylogenetic analyses and haplotype networks revealed distinct clades for each taxon, and significant phylogeographic structure highlighted the role of geographic factors in fostering genetic differentiation. Morphologically, the presence of hairs inside the calyx tube ( S. honania ) and on the anther surface ( S. meiliensis ) were found to be reliable diagnostic characters for species identification. We conclude that S. honania and S. meiliensis are independently evolving lineages, likely in the early stages of speciation. This study illustrates recent and ongoing speciation in two herbaceous plants with narrow distributions and morphological similarities. It underscores the importance of integrative taxonomy for accurate species delimitation within genetically divergent but morphologically similar lineages.