Abstract
Speciation arises from multifaceted factors, making phenotype-based classifications unreliable. Integrative taxonomy has advanced significant breakthroughs in taxonomically challenging groups like Apiaceae, which is characterized by highly convergent morphological traits across species. The genus Eriocycla (Apiaceae) has long presented persistent taxonomic uncertainties. While morphological similarities initially supported Eriocycla as Seseli sect. Eriocycla, phylogenetic studies consistently resolve Eriocycla within the tribe Echinophoreae, contrasting with Seseli (tribe Selineae). Integrated morphological and molecular analyses were conducted here to resolve this taxonomic conflict. Phylogenetic reconstructions based on nuclear ribosomal DNA and plastomes all supported that Seseli delavayi and Seseli nortonii formed a stable monophyletic group with Eriocycla nuda and Eriocycla pelliotii within Echinophoreae, separate from Seseli. Plastome comparisons across 14 taxa revealed structural conservation in E. nuda, E. pelliotii, S. delavayi, and S. nortonii, particularly in inverted-repeat and single-copy regions, distinct from that of other Seseli species. A unique inversion involving the trnY-GUA, trnD-GUC, and trnE-UUC genes was detected in E. nuda and E. pelliotii but absent in S. delavayi and S. nortonii. Shared morphological characteristics, including glabrous stem bases, basally free bracteoles, and prominent calyx teeth, further support their affinity with Eriocycla. We therefore propose to recognize Eriocycla as a separate genus rather than as Seseli sect. Eriocycla and reclassifying S. delavayi and S. nortonii into it. In conclusion, this study not only revealed the phylogenetic position of the tribe Echinophoreae but also resolved the long-standing taxonomic controversy surrounding Eriocycla and Seseli.