Abstract: Understanding plant diversity and the phylogenetic divergences in the Northern Hemisphere is essential for in-depth evolutionary studies and conservation efforts. Maianthemum is an ideal example to explore plant diversification processes in the Northern Hemisphere, with more than 35 species widely distributed in forests in North to Central America, Europe and eastern Asia. Yet the phylogenetic relationships within Maianthemum remain elusive. In this study, we reconstructed a well-supported phylogenetic framework of Maianthemum and explored possible gene introgressions and reticulate evolution using nuclear and chloroplast genomes based on the target enrichment Hyb-Seq approach. Both nuclear and chloroplast phylogenetic results supported three clusters corresponding to their biogeographic distribution of the New World, the Himalayan-Hengduan Mountains, and the north temperate zone, respectively. The genus was inferred to be most likely originated in North America with migrations into Central America and eastern Asia in the late Miocene. Our results suggested that both incomplete lineage sorting and hybridizations/introgressions along with geographic isolation have contributed to the rapid divergence of Maianthemum in eastern Asia, which may represent a complex model for the evolutionary radiation of plants in eastern Asia and even the Northern Hemisphere.

Key words: Asparagaceae, Himalayan-Hengduan Mountain, Maianthemum, phylogenomics, reticulate evolution