Testing reticulate evolution of four Vitis species from East Asia using restriction-site associated DNA sequencing

U Reticulate evolution is an important driving force of angiosperm evolution. It has been proposed as an important evolutionary process in Vitis L. subgenus Vitis. Events of natural hybridization and introgression of several taxa native to North America have been hypothesized and discussed. However, there is no convincing evidence of reticulate evolution reported for closely related Vitis taxa from East Asia. We aim to explore natural hybridization and introgression among four closely related Vitis taxa from East Asia (V. amurensis Ruprecht, V. romanetii Romanet du Caillaud, V. shenxiensis C. L. Li, and V. piasezkii Maximowicz) with the restriction-site associated DNA sequencing technique. A total of 46 accessions, covering the potential morphological and geographic variation of each species, are sequenced. Our results show a complex evolutionary pattern of the four Vitis species. The phylogenetic inference suggests that V. amurensis is monophyletic, however, V. romanetii, V. shenxiensis, and V. piasezkii do not appear to be monophyletic. Significant signals of introgression in some accessions have been detected by population structure analyses. D-statistics analysis and population structure analyses support the presence of introgression between V. shenxiensis/V. piasezkii and V. romanetii in sympatric populations, but a strong signal of admixture has not been recognized between distantly located populations. Our results provide strong evidence of reticulate evolution among V. romanetii, V. shenxiensis, and V. piasezkii.