Plant Diversity ›› 2023, Vol. 45 ›› Issue (04): 434-445.DOI: 10.1016/j.pld.2022.08.002

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Late Oligocene fossil acorns and nuts of Quercus section Cyclobalanopsis from the Nanning Basin, Guangxi, South China

Xiao-Yan Liua,b, Han-Zhang Songa, Xin-Kai Wuc, Jia-Rong Hua, Wei-Ye Huanga, Cheng Quand, Jian-Hua Jina   

  1. a. State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China;
    b. School of Geography, South China Normal University, Guangzhou 510631, China;
    c. State Key Laboratory of Biocontrol, School of Ecology, Sun Yat-sen University, Guangzhou 510275, China;
    d. School of Earth Science and Resources, Chang'an University, Xi'an 710054, China
  • Received:2021-12-31 Revised:2022-07-15 Online:2023-07-25 Published:2023-08-21
  • Contact: Cheng Quan,;Jian-Hua Jin,
  • Supported by:
    This study was supported by the National Natural Science Foundation of China (Nos. 41872015, 31770241, 41820104002, and 41661134049), and the grant of the Natural Environment Research Council of Research Councils UK (No. NE/P013805/1). We sincerely thank post-doctoral fellows and graduate students majoring in Ecology and Botany at Sun Yat-sen University for participating in collecting the fossils in the field; Dr. Yi-Gang Song from Shanghai Chenshan Plant Science Research Center (CAS) for providing many acorns of extant species of Quercus section Cyclobalanopsis for comparison, and discussing the identification of the fossils; the staff of the herbaria of Harvard University, Florida Museum of Natural History, South China Botanical Garden, and Sun Yat-sen University for permission to examine and photograph the extant specimens of Fagaceae. We are very grateful to Prof. Robert A. Spicer from Open University and Prof. Steven R. Manchester from Florida Museum of Natural History, University of Florida, USA for their helpful comments and language help, and Ms. Su-Ping Wu from the Experimental Technologies Center of Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, China for her assistance in CT scanning.

Abstract: Quercus is the largest genus within the Fagaceae and has a rich fossil record. Most of the fossil material is attributed to the subgenus Quercus based on leaves, pollen or rarely acorns and nuts. Fossil records of Q. section Cyclobalanopsis characterized by ring-cupped acorns are relatively few and especially those described based on nuts are scant. In this study, we described four new species of Quercus section Cyclobalanopsis based on mummified acorns and nuts: Q. paleodisciformis X.Y. Liu et J.H. Jin sp. nov., Q. paleohui X.Y. Liu et J.H. Jin sp. nov., Q. nanningensis X.Y. Liu et J.H. Jin sp. nov. and Q. yongningensis X.Y. Liu et J.H. Jin sp. nov. These species closely resemble the extant species Q. disciformis, Q. hui, Q. kerrii, and Q. dinghuensis. The occurrence of Q. section Cyclobalanopsis in the Oligocene stratum of Guangxi, South China, suggests that the section has diversified within its extant distribution center since the Oligocene. By combining records from other areas, we propose that the section first appeared in the middle Eocene of East Asia (Sino-Japan), has diversified in situ with a few elements scattering into West Asia and southern Europe since the Oligocene and Pliocene, respectively, and finally became restricted in East Asia since the Pleistocene. This indicates that the section originated and diversified in East Asia, before spreading into West Asia no later than the Oligocene and into southern Europe by the Pliocene. Subsequently it disappeared from South Europe and West Asia due to the appearance of the (summer dry) Mediterranean climate and widespread cooling during the Pleistocene.

Key words: Quercus section Cyclobalanopsis, Fossil acorn and nut, Oligocene, Guangxi, South China