Format: ORAL

Wen-Na Ding1,2, Richard H. Ree3, Michael R. May4, Alex Skeels5, Philipp Brun2, Loc Pellissier2,6, Yao-Wu Xing1, Niklaus E. Zimmermann2

1 CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China. 2 Swiss Federal Institute for Forest, Snow and Landscape Research WSL, 8903 Birmensdorf, Switzerland. 3 Negaunee Integrative Research Center, Field Museum, 1400 S Lake Shore Drive, Chicago, IL 60605, USA. 4 University Herbarium and Department of Integrative Biology, University of California, Berkeley. 5 Research School of Biology, Australian National University, Canberra 0200, Australia 6 Department of Environmental Systems Science, Ecosystems and Landscape Evolution, Institute of Terrestrial Ecosystems, ETH Zurich, 8092 Zurich, Switzerland.

The alpine biota above the treeline of the high mountains harbors unique floristic characters adapted to stressful environments and provides critical ecosystem services to our society. Yet, the origin, assembly pattern, and biotic interchange across different mountain regions remain enigmatic. Here, we investigated the diversification and assembly history of alpine biotas in the Northern Hemisphere aligning with paleoenvironmental changes. Our findings reveal that the alpine biodiversity is disproportionally assembled by colonization and in situ diversification. Alpine lineages initially diversified in the Tibet-Hengduan-Himalaya (THH) region as early as the Oligocene, playing a pivotal role as the primary source of alpine flora until it was overtaken by the arctic-boreal region by the Pliocene. The diversity of alpine plants in other major mountains of the Northern Hemisphere began accumulating since the early to middle Miocene, but significantly diversified until climatically suitable habitats expanded towards the end of the Miocene. Our study highlights the significant role of the THH region as both the cradle and museum of cold-adapted plants, with a subsequent increase in the importance of the arctic-boreal region.