The evolutionary history and phylogeographic pattern of Hippuris vulgaris: hybridization and long-distance dispersal from China

Hippuris vulgaris is a widespread aquatic plant in the Northern Hemisphere. Phylogenetic analysis on a low-copy nuclear gene (PHYB) indicated that this species originated from a hybridization between two unknown ancestral parents. Two distinct lineages (I and II) were detected using chloroplast intergenic regions, and their divergence time was 1.51 Ma. Lineage I was composed of the populations from North China, Qinghai-Tibetan Plateau (QTP), and Europe while lineage II included the populations from North China, Europe and Japan. Based on the results of the Bayesian binary MCMC (BBM) analysis, QTP was likely the original center of these two lineages. The possible dispersal route for lineage I was inferred to be directly from QTP to North China and Europe, respectively, while lineage II likely dispersed first to Japan and from there moved separately to North China and Europe. In this study, we illustrate two important evolutionary events of H. vulgaris: hybridization and long-distance dispersals.