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

Abstract

Ainsliaea is 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 Ainsliaea have been classified into two sections, A. sect. Ainsliaea and 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 Ainsliaea with two more samples of the highly variable A. lancifolia and a new sampling of A. nana. Habit variations in Ainsliaea were 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. uniflora and A. lancifolia form 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. pertyoides forms another large clade with the rosulate‐leaf species. The latter three species have distinct habits: A. lancifolia with leaves sparsely alternate along the stem but often reduced to a basal rosette in rheophytic environments, A. nana with leaves aggregated at and also above the same stem base, and A. pertyoides with rosulate leaves when young. Thus, two new sections, A. sect. Alternae sect. nov. and A. sect. Intermediae sect. nov., are proposed to accommodate A. lancifolia and A. nana, respectively, and A. pertyoides is reasonably kept in A. sect. Ainsliaea. The results of this study provide insights into the evolution of habits in Ainsliaea and suggest that the traditional classification based solely on habit may not accurately mirror the evolutionary history of the genus. The newly proposed A. sect. Alternae and sect. Intermediae reflect a more natural classification of Ainsliaea and 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. nana and A. pertyoides are provided. Overall, this study highlights the importance of combining molecular and morphological data to accurately classify and understand the evolutionary history of plant groups.