Insights into Phylogeny, Taxonomy, Origins and Evolution of and , Based on Comparative Chloroplast Genome Analysis.

Hawthorns ( L.) are widely distributed and well known for their medicinal properties and health benefits. Nevertheless, the phylogenetic relationships among native to China remain unclear. Additionally, no consensus exists on the origin and evolution of , and the relationship between and is is unclear. Here, we sequenced 20 chloroplast (cp) genomes (19 from and 1 from ) and combined them with 2 existing cp genomes to investigate the phylogenetic relationships, divergence times and biogeographic history of . Four hypervariable loci emerged from the newly sequenced genomes. The phylogenetic results indicated that the 14 Chinese species analyzed clustered into two clades. One clade and the North American species grouped together, while the other clade grouped with the European species. Our results favor recognizing and as one genus. Molecular dating and biogeographic analyses showed that originated in Southwest China during the early Oligocene, approximately 30.23 Ma ago. Transoceanic migration of East Asian species across the Bering land bridge led to the development of North American species, whereas westward migration of the ancestors of drove the formation of European species. may represent the earliest lineage of Chinese . The uplift of the Qinghai-Tibet Plateau (QTP) and the Asian monsoon system may have led the ancestors of in south-western China to migrate toward the northeast, giving rise to other Chinese species. This study offers crucial insights into the origins of and proposes an evolutionary model for the genus.