Fagaceae from the plant assemblage of Badaogou, Jilin Province, China (late Pliocene) indicate post-Pliocene diversification of oaks
Kovar-Eder, Johanna; Kern, Andrea K.; Sun, Ge
published: Dec 18, 2015
The fossil plant assemblage from the Ma’anshancun Formation of Badaogou, Changbai Shan, Changbai County, Jilin Province, China, contains organically preserved foliage remains and palynomorphs. Most recent Ar/Ar datings indicate an age for the plant-bearing diatomites around the Plio-/Pleistocene turn (2.463 ± 0.0075 to 2.649 ± 0.006 m.a.), i.e., ~13–16 m.a. younger than previously thought. Here we present the results on the Fagaceae. Four different fossil species of oaks are distinguished by foliage based on gross morphology and well-preserved cuticles, while other genera are absent in the leaf record. The pollen record includes four types of Quercus and three of Fagus. Castanea pollen is present though in percentages < 1 %. the diagnosis of Quercus changbaiensis C. Z. Zhang is emended and a neotype has been determined. Quercus waltheri Kovar-Eder sp. nov. and Q. maii Kovar-Eder sp. nov. are described as new fossil species. Quercus sp. is based solely on one leaf fragment. Comparison with the European Neogene record provides evidence that Q. changbaiensis resembles Q. pseudocastanea grossmorphologically but differs in its cuticle structures, while Q. waltheri closely resembles Q. gigas both in gross- and micromorphology. For Q. maii, no closely matching European fossil species has been identified. We conducted a far-reaching comparison with modern oaks mainly from East Asia and identified diagnostically relevant features of trichome base structure and of trichome surface ornamentation. The most similar living relatives of the here described oaks cannot be identified unambiguously. Based on this fact and the strong hybridisation tendencies among deciduous oaks today, we conclude that the modern species richness largely resulted from intensive diversification and hybridisation during the Quaternary.