Diversity of Fagaceae on Hainan Island of South China During the Middle Eocene: Implications for Phytogeography and Paleoecology

Xiaoyan Liu,Jianhua Jin,Hanzhang Song

doi:10.3389/fevo.2020.00255

Abstract

The Fagaceae family is currently widespread throughout tropical and temperate regions of South America and the Northern Hemisphere, especially East Asia, and has likely been so since the Eocene, according to fossil records. In China, Fagaceae fossils are rare in the lowest latitudes of South China. Here, we describe 12 species in 5 genera of Fagaceae (i.e. Berryophyllum, Castaneophyllum, Quercus, Castanopsis and Lithocarpus) based on leaf morphology and trichomes. These fossils are recovered from the Changchang Formation of Changchang Basin, Hainan Island, South China, indicating that Fagaceae has been distributed in these tropical low latitudes since the Eocene. Given that our fossils are closely related to the tropical and subtropical extant species, we speculate that Fagaceae lineages have likely diverged since the Eocene and that each extant lineage, such as Quercus sect. Cyclobalanopsis, became highly differentiated no later than middle Eocene. Based on the current living conditions of the extant species, we further speculate that the climate of Hainan Island was warm and wet during the middle Eocene, suitable for the growth and differentiation of the family.

Highlights

The woody angiosperms family Fagaceae, which includes beeches and oaks, defines the structure of subtropical and tropical evergreen forests (Tang, 2015; Wilf et al, 2019)
We studied 41 leaf fossils of Fagaceae recovered from the middle Eocene of Changchang Formation, Changchang Basin, Hainan Island, South China
Published fossil records indicate that Berryophyllum was widely distributed in strata from the Paleocene to the Eocene in Asia, North America, and Europe (Figure 14A; Writing Group of Cenozoic Plants of China [WGCPC], 1978; Takhtajan, 1982; Jones and Dilcher, 1988; Crepet and Nixon, 1989a; Mai, 1995; Zhou, 1996; Tao et al, 2000; Kvacek and Walther, 2010)

Summary

Introduction

The woody angiosperms family Fagaceae, which includes beeches and oaks, defines the structure of subtropical and tropical evergreen forests (Tang, 2015; Wilf et al, 2019). The family is subdivided into ten extant genera: Fagus L., Formanodendron Nixon et Crepet, Trigonobalanus Forman, Colombobalanus Nixon et Crepet, Castanopsis Subtropical, and tropical regions of the Northern Hemisphere and South America (Huang et al, 1999; Chen, 2007), Fagaceae is most diverse in South and Southeast Asia and North America (Zhou, 1999; Chen, 2007; Denk et al, 2017; Xu et al, 2019). Of the approximately 927 species in 10 genera, China hosts 294 species in 6 genera: Fagus, Formanodendron, Castanopsis, Castanea, Lithocarpus, and Quercus, most of which are found in South and Southwest China (Li, 1996; Huang et al, 1999). Characterizing the evolution and distribution of Fagaceae in this region is important for understanding this keystone family

Methods

Results

Conclusion