J Syst Evol ›› 2021, Vol. 59 ›› Issue (1): 216-226.DOI: 10.1111/jse.12518

• Research Articles • Previous Articles     Next Articles

First fossil record of an East Asian endemic genus Sladenia (Sladeniaceae) from its modern range: Implications for floristic evolution and conservation biology

Lin‐Bo Jia1, Steven R. Manchester2, Jian Huang3, Tao Su3,4, Li Xue5, Shi‐Tao Zhang5, Yong‐Jiang Huang1*, and Zhe‐Kun Zhou1,3*   

  1. 1CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China
    2Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611‐7800, USA
    3Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, Yunnan, China
    4University of the Chinese Academy of Sciences, Beijing 100049, China
    5Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming 650093, China
  • Received:2019-01-18 Accepted:2019-05-13 Online:2019-06-05 Published:2021-01-01

Abstract: Fossil records of endemic plants play an important role in recognizing the floristic history of East Asia and thereby facilitate the conservation of plant diversity in the region. However, the fossil record of many extant East Asian endemic genera remains poorly documented thus far. Here, we report an infructescence fossil of an East Asian endemic genus, Sladenia (Sladeniaceae), from the early Miocene of southeastern Yunnan, China. The fossil is characterized by: (i) dichasial cymes; and (ii) flask‐shaped ovary with dense subparallel ribs on the surface extending from the base to the distal end of the united style. It represents the first fossil record of Sladenia in Asia, showing that the genus was established in the region at least by the early Miocene. Given that a much older fossil record of Sladeniaceae has been reported from Africa and the sister group of Sladenia is distributed only in Africa, Sladenia is not likely of East Asian origin. The present endemic status of Sladenia was possibly achieved by regional extirpation in Africa and taking refuge in East Asia. This case thus supports the “Museum” rather than “Cradle” hypothesis for the genesis of high plant species in the flora of East Asia. A comparison of the present fossil with extant Sladenia infructescence shows morphological stasis from the early Miocene to present. Such evolutionary tardiness might have resulted in the reduced fitness of the genus, which further caused its current endangered situation.

Key words: conservation, endemic plant, morphological stasis, phytogeography, Sladenia