Work

Phylogenomics, reticulate evolution, and taxonomic revision of East Asian Cardamine (Brassicaceae) in the Hengduan biodiversity hotspot

Year: 2026

Type: article

Abstract: The genus Cardamine (Brassicaceae) exhibits remarkable species diversity and endemism in the Hengduan-Himalayan Mountains (HHM) of East Asia; however, its phylogenetic relationships and evolutionary history remain unclear. Here, we conducted a phylogenomic analysis of 50 species, including 45 East Asian Cardamine taxa and five Loxostemon species, based on complete chloroplast genomes and 1,081 single-copy nuclear genes. Our results indicate that: (1) Cardamine is not monophyletic, with Loxostemon nested within the genus; moreover, the diagnostic morphological characters traditionally used to delimit Loxostemon have evolved repeatedly and independently, supporting its synonymization under Cardamine. (2) Divergence time estimation and ancestral range reconstruction suggest that the core HHM clade originated approximately 4.34 Ma and rapidly radiated between 4.34 and 1.86 Ma, temporally coincident with major uplift events of the Qinghai-Tibet plateau (QTP). Integrative analyses of gene tree discordance, hybridization signals, and ploidy variation further demonstrate that this rapid diversification was driven by reticulate evolution involving incomplete lineage sorting and frequent hybridization. This study provides the first genome-scale phylogeny framework for East Asian Cardamine, highlights the central role of hybridization in generating plant diversity in the HHM, and offers a robust molecular foundation for future taxonomic revision.

Source: Molecular Phylogenetics and Evolution

DOI: 10.1016/j.ympev.2026.108647