An updated phylogeny of Ainsliaea(Asteraceae: Pertyoideae) and its implications for classification and habit evolution

Ainsliaeais an Eastern Asian genus with approximately 50 species, and is characterized by two main habit types or leaf arrangements: rosulate with leaves aggregated at the stem base or pseudo‐verticillate with leaves clustered above the stem base. Most species of Ainsliaeahave been classified into two sections, A.sect. Ainsliaeaand sect. Aggregatae, respectively, based on their habit type. However, recent molecular phylogenetic studies have challenged existing infrageneric classifications for Ainsliaea, and the systematic value of habit needs to be re‐evaluated because the habits of some key species were described differently, leading to taxonomic controversies on infrageneric classifications and species delimitations. To address these issues, this study reconstructed a more comprehensive phylogeny of Ainsliaeawith two more samples of the highly variable A. lancifoliaand a new sampling of A. nana. Habit variations in Ainsliaeawere observed both in the field and in herbarium collections, and habit evolution was reconsidered based on the updated phylogeny. The phylogenetic analysis highly supports that A. unifloraand A. lancifoliaform the first‐ and the second‐earliest diverging lineages in Ainsliaea, respectively; A. nana, recently rediscovered by us after more than 60 years, constitutes a distinct lineage sister to a large clade with all leaves aggregated above the stem base; and A. pertyoidesforms another large clade with the rosulate‐leaf species. The latter three species have distinct habits: A. lancifoliawith leaves sparsely alternate along the stem but often reduced to a basal rosette in rheophytic environments, A. nanawith leaves aggregated at and also above the same stem base, and A. pertyoideswith rosulate leaves when young. Thus, two new sections, A.sect. Alternaesect. nov. and A.sect. Intermediaesect. nov., are proposed to accommodate A. lancifoliaand A. nana, respectively, and A. pertyoidesis reasonably kept in A.sect. Ainsliaea. The results of this study provide insights into the evolution of habits in Ainsliaeaand suggest that the traditional classification based solely on habit may not accurately mirror the evolutionary history of the genus. The newly proposed A.sect. Alternaeand sect. Intermediaereflect a more natural classification of Ainsliaeaand provide a framework for future studies on the evolution and ecology of the genus. Combining evidence from phylogeny and morphology, a conspectus of the genus and taxonomic updates for A. lancifolia, A. nanaand A. pertyoidesare provided. Overall, this study highlights the importance of combining molecular and morphological data to accurately classify and understand the evolutionary history of plant groups.