Revisiting the phylogeny of Conioselinum (Apiaceae) by integrating nrDNA, plastomes and morphology evidence

BACKGROUND: The genus Conioselinum Fisch. ex Hoffm. (Apiaceae) presents long-standing taxonomic challenges due to poorly resolved infrageneric relationships and significant morphological convergence with related genera such as Ligusticum s.l. Although integrating plastomes and nrDNA data has been effective in resolving complex phylogenies, a comprehensive phylogenetic framework and a critical reevaluation of key diagnostic traits for Conioselinum remain insufficient. RESULTS: Our nrDNA phylogeny established a robust framework supporting the monophyly of Conioselinum as nested within the Hymenidium clade, delineating three distinct subclades (A, B, and C). This phylogenetic framework is further corroborated by corresponding morphological traits. We reaffirmed that the terminal localization of vascular bundles in fruit ribs is a stable synapomorphy for Conioselinum, when integrated with a consistent suite of diagnostic markers—specifically deciduous basal leaves, linear bracteoles, and absent or obsolete calyx teeth—it effectively distinguishes the genus from closely related allies. Divergence time estimation traced a rapid radiation from the Late Miocene to the Pleistocene, coinciding with the Qinghai-Tibet Plateau uplift. Furthermore, selective pressure analyses identified positive or relaxed selection in six genes (ycf1, matK, rpoA, ycf2, rps7, and ccsA), suggesting their role in adapting to alpine environmental stresses. Evident cytonuclear conflicts in some taxa underscore a complex history likely involving reticulate evolution. CONCLUSION: This study highlights the utility of integrating phylogenomics with morphology to resolve complex taxonomies. Based on congruent evidence from both sources, we propose a revised circumscription for Conioselinum. Together, these molecular and morphological insights establish a solid foundation for future taxonomic revisions and enhance our understanding of adaptive diversification in Apiaceae.