Molecular phylogeny and biogeography of the genus Tulipa (Amana spp.) in East Asia.

The East Asian tulips (Amana spp.), which are endemic to East Asia, include the species A. edulis, recognized as the source of the traditional Chinese medicine (TCM) known as "Guangcigu." In this study, we collected 50 samples representing six Amana species: A. edulis, A. erythronioides, A. anhuiensis, A. kuocangshanica, A. wanzhensis, and A. baohuaensis, across China and sequenced their complete chloroplast genomes. Phylogenetic analyses based on 74 shared protein-coding sequences in the chloroplast genome, along with divergence time estimations and biogeographic studies, have yielded several key findings. First, Amana spp. is confirmed to be monophyletic, having originated in the Late Miocene approximately 95% confidence interval of 5.63-12.52 million years ago, with diversification occurring within the 95% confidence interval of 2.36-4.68 million years ago in the mid-Pliocene, primarily in the Anhui and Zhejiang provinces. Second, Amana spp. comprise six valid species, each exhibiting varying degrees of dispersal into adjacent regions. Third, A. edulis, which emerged in the mid-Pliocene, has significantly expanded its range, colonizing the western parts of Jiangsu, Henan, and Jiangxi provinces and extending into northeastern China, North Korea, and Japan. This broad distribution, in comparison to other Amana species, is likely attributable to the evolutionary effects of the East Asian monsoon climate, which was intensified by the uplift of the Qinghai-Tibet Plateau. Analysis of chloroplast DNA markers revealed notable differences between A. edulis and other species, providing a reliable method for identifying Guangcigu and ensuring the safe use of this TCM.