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.