Neogene oak diversity of southeast United States: pollen evidence from the Gray Fossil Site

Abstract

Pollen micromorphology provides one of the only morphological features characterising the phylogenetic lineages in oaks; therefore it is of great potential in understanding oak diversity in the geological past. In the present study, scanning electron microscopy (SEM) observations were made on the late Neogene pollen flora recovered from the well-known Gray Fossil Site in Tennessee, southeast United States. Four pollen types were recognised in the light of details of pollen tectum sculpturing, which are assigned to the white or the red oaks. These taxa were morphologically compared with those of modern oaks in the region. The presence of at least four pollen types of oaks further confirms the diverse and dynamic oak-hickory forest in southern Appalachian during the late Neogene. Furthermore, such a high diversity of oak pollen types indicates that the ancient oak-hickory forest must have sustained a late Neogene biota highly comparable to that of the modern ecosystem in southeast United States.

Keywords:

• Quercus
• pollen micromorphology
• SEM
• diversity
• southeast United States

Acknowledgements

The authors would like to thank Dr David K. Ferguson for his invitation to this special Festschrift to commemorate the retirement of Dr Reinhard Zetter, who is specially thanked for his mentorship jointly with Dr David K. Ferguson to the first author, great passion and diligent work, which has increasingly transformed palynology and palaeopalynology over the past three decades. Thanks are also due to Dr Frosty Levy for sharing his first-hand knowledge of the regional oak floristics in southeast United States. This work was supported by the US NSF grant EAR 0746105 awarded to Y.-S. (C.) Liu and China NSFC No. 41820104002 to C. Quan.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (41820104002); National Science Foundation (EAR 0746105).