%A Linbo Jia, Tao Su, Weicheng Li, Shufeng Li, Yongjiang Huang, Zhekun Zhou %T The floristic differentiation of Southwest China: Insights from Cedrelospermum and Ailanthus fossils %0 Journal Article %D 2022 %J Biodiv Sci %R 10.17520/biods.2022348 %P 22348- %V 30 %N 11 %U {https://www.biodiversity-science.net/CN/abstract/article_82864.shtml} %8 2022-11-20 %X

Aims: Northwest Yunnan-Xizang and Southeast Yunnan-West Guangxi are two regions with distinct differences in pedigree age and appearance in southwestern China. The two regions are characterized by young flora dominated by herbaceous plants and ancient flora dominated by woody plants, respectively. It is unknown how the floristic differentiation of these two regions has formed.

Methods: We report new fossil records of Cedrelospermum and Ailanthus from the two study regions. We also review the fossil history of the two genera, particularly those in Southwest China.

Results: The fossil history of the two genera in Southwest China is as follows: Cedrelospermum occurred in the middle Eocene to late Oligocene of Xizang (C. tibetica) and the late Eocene of Southeast Yunnan (C. asiaticum). Ailanthus appeared in the middle Eocene to late Oligocene of Xizang (A. maximus) and the late Eocene of Southeast Yunnan (A. confucii). Our results show that both Northwest Yunnan-Xizang and Southeast Yunnan-West Guangxi floras grew Cedrelospermum and Ailanthus in the Paleogene, but the species are different since the late Eocene.

Conclusion: The genus level similarity of Northwest Yunnan-Xizang and Southeast Yunnan-West Guangxi floras support the hypothesis that floristic exchanges have occurred between the two regions. However, the difference in species indicates that the two floras have separated from each other since or before the late Eocene due to environmental differentiation. The woody Cedrelospermum and Ailanthus have disappeared from Xizang, and have been replaced by a generally younger herbaceous flora. In contrast, Ailanthus occurs presently in Southeast Yunnan, providing evidence for the archaic nature of the flora. Our study provides fossil evidence for the similarity and differentiation of the floras of Northwest Yunnan-Xizang and Southeast Yunnan-West Guangxi in the geological past.