Format: ORAL

Lianming Gao1,4, Chaonan Fu1,2, Hongtao Li2, Zhiqiong Mo1,3, Mingshu Zhu1,3, Tingshuang Yi2, Dezhu Li2

1 CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, China 2 Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, China 3 University of Chinese Academy of Sciences, Beijing 100049, China 4 Lijiang Forest Biodiversity National Observation and Research Station, Kunming Institute of Botany, Chinese Academy of Sciences, Lijiang 674100, Yunnan, China

The Hengduan Mountains, also named Mountains of Southwest China (MSC), is one of the global biodiversity hotspots with the most extensively elevated surface on Earth, harboring around 10840 seed plant species from 1542 genera and 194 families. The origin and evolutionary history of the Hengduan Mountains flora remains unclear. We analyzed a time-calibrated phylogenetic tree of over 21000 seed plant species with 206 fossil calibrations based on 80 plastid genomic genes to investigate the evolutionary history and species diversification covering over 70% seed plant species from the Hengduan Mountains (7663 species from 1435 genera and 194 families). Our results showed that extant lineages (genera) in the Hengduan Mountains mainly immigrated from other floras and emerged after the early Oligocene. The rapid species diversification and accelerated diversification took place after the middle Miocene (ca. 15 Ma, million years ago), especially in Pliocene (5.32.6 Ma) and Pleistocene (2.60.1 Ma), and the regional endemic species had the similar diversification pattern, which was likely driven jointly by mountain building, intensification of the Asian monsoon, Neogene climate cooling, and Quaternary climate fluctuations. The results of the molecular dating, species diversification, and ancestralareareconstruction analyseson nine representative genera of seed plants showed that the early lineages mainly immigrated from other floristic regions, and accelerated from early Miocene (ca. 20 Ma), and peaked in ca. 5 Ma, mainly from the Saharo-Arabian realm. The in situ speciation with an increased rate of in situ speciation started from the later Miocene-early Pliocene to Pleistocene, likely triggered by Hengduan Mountains orogeny, the intensified Asian summer monsoon, and Quaternary climate fluctuations.