East Asian subtropical evergreen broadleaved forests act as a cradle for understory herbaceous diversity: A case study of Epimedium (Berberidaceae)

Hai, Lisi

PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY

2026

697

Wang, W;Meng, HH

East Asian subtropical evergreen broadleaved forests (EBLFs) harbor high levels of biodiversity and endemism. Unlike the well-studied woody plant groups in this biome, we know little about the macroevolutionary processes underlying species richness of understory herbaceous groups in this biome. The herbaceous genus Epimedium, comprising approximately 60 species, is widely distributed across the Eurasia and is an important understory component of East Asian subtropical EBLFs. Here, we present, to our knowledge, the most comprehensive phylogenetic analysis of Epimedium to date based on twelve nuclear and plastid loci. We estimated divergence times, ancestral ranges, and rates of diversification, and inferred the evolutionary shifts of habitats and ecological niches. Our results suggest that the split of East Asian Epimedium and western North American Vancouveria occurred at about 10 Ma, associated with climatic niche differentiation. We inferred four dispersals and four vicariance events to explain the current distribution of Epimedium. East Asia is the source area for Eurasian Epimedium diversity, and West Asia acted as the stepstone for range expansion of this genus. Epimedium experienced a rapid diversification in East Asian subtropical EBLFs at about 4 Ma, which contributed to the overwhelming majority of species diversity of the genus. The tectonic activities, the intensification of East Asian monsoon, and the development of EBLFs drove jointly the diversification of Epimedium in East Asian subtropical EBLFs. Our findings suggest that East Asian subtropical EBLFs serve as an evolutionary cradle for the diversity of Epimedium and likely other understory herbaceous groups.