Phylogenetic relationships and divergence time of Hydrangea sect. Macrophyllae (Hydrangeaceae) revealed by genome-wide SNPs

Hydrangea sect. Macrophyllae comprises deciduous shrubs including two species with seven infraspecific taxa distributed throughout the Japanese Archipelago and adjacent areas. In this study, we revealed a phylogeny of Hydrangea sect. Macrophyllae by using a larger dataset of genome-wide SNPs than those employed in a previous study and by adding more comprehensive taxa/populations, which cover the entire distribution of the section. We then revised the taxonomic treatment of sect. Macrophyllae based on the higher-resolution phylogenetic trees obtained in this study. The phylogenetic trees estimated in this study showed five major clades, suggesting that H. serrata var. minamitanii and var. yesoensis should be treated as independent species from other H. serrata, that H. serrata var. australis and var. yakushimensis could be subclassified under the major clades and that var. angustata could be a synonym of var. serrata. The divergence time of these major clades was estimated to be in the Pleistocene.