From phylogenomic backbone to infrageneric classification in Adenophora (Campanulaceae): dense plastid sampling supports an evidence-based infrageneric system

Dense amplicon sampling substantially improved species-by-clade resolution across Adenophora and helped bridge the gap between phylogenomic backbone inference and infrageneric classification. Interpreted together with historical classifications, filtered morphology, species-complex evidence, and nomenclatural considerations, the recovered framework supports a broadened circumscription of Adenophora, including the former genus Hanabusaya, and an infrageneric system comprising three subgenera, seven sections within subg.

Adenophora, and five well-supported subsections within sect. Adenophora. This framework includes two new subgenera at new rank, three new sections, and the retention or restoration of historically available infrageneric names where they can be linked to stable lineages and implemented nomenclaturally.

More broadly, this study shows that amplicon sequencing is most useful not as a replacement for genome-scale phylogenomics, but as a dense membership-mapping layer that makes broad phylogenomic backbones classificatorily operational. It further supports an evidence-chain strategy for formal classification in conflict-rich lineages.