New Fagaceous pollen taxa from the Miocene Søby flora of Denmark and their biogeographic implications

Abstract

The Fagaceae comprise around 1000 tree species in the Northern Hemisphere. Despite an extensive fossil pollen record, reconstructing biogeographic patterns is hampered because it is difficult to achieve good taxonomic resolution with light microscopy alone. We investigate dispersed pollen of Fagaceae from the Miocene Søby flora, Denmark. We explore the latitudinal gradient in Fagaceae distribution during the Miocene Climatic Optimum (MCO) in Europe and the Northern Hemisphere to compare it with the Eocene Warmhouse and the present. Methods: We investigated dispersed pollen using light and scanning electron microscopy. We assessed biogeographic patterns in Fagaceae during two warm periods in Earth history (MCO, Eocene) and the present. Results: Eight species of Fagaceae were recognized in the Søby flora. Of these, Fagus had a continuous Mediterranean to subarctic distribution during MCO; Quercus sect. Cerris and castaneoids had northern limits in Denmark, and evergreen Quercus sect. Ilex in Central Europe. In a northern hemispheric context, Fagus and sections of Quercus had more northerly distribution limits during Eocene and MCO with maximum northward extensions during Eocene (Fagus, castaneoids) or Oligo-Miocene (Quercus sects. Cerris and Ilex). The known distribution of the extinct Tricolporopollenites theacoides during MCO included Central Europe and East China, while this taxon thrived in South China during Eocene. Conclusions: More northerly distributions during MCO and Eocene probably were determined by temperature. In contrast, fossil occurrences in areas that are arid or semi-humid today were determined by maritime conditions in these areas (western North America, Central Asia) during the Cenozoic.

Niche evolution in a northern temperate tree lineage: biogeographical legacies in cork oaks (Quercus section Cerris)

“…A rapid origin and spread with gene flow between lineages is also supported by the low plastid differentiation, decoupled from main intrasectional lineages (subsections) and species. Cerris oaks then became relatively widespread ( Quercus kubinyii ) in Western Eurasia during the Middle Miocene, ranging from Denmark to Anatolia ( Kováts, 1856 ; Christensen, 1976 ; Knobloch, 1986 ; Güner et al , 2017 ; Denk and Bouchal, 2021 ). These leaf remains resemble modern species of section Cerris that possess ancestral leaf types ( Fig.…”

Advances in Swedish palaeontology; the importance of fossils in natural history collections - The Department of Palaeobiology at the Swedish Museum of Natural History

“…Despite the lack of plant remains from the mid-Cenozoic from Sweden, Denmark hosts extensive, fossiliferous deposits representing this time interval (Larsson et al 2011) and the Department of Palaeobotany has a well-curated collection from the Søby-Fasterholt area in Central Jutland, Denmark (Friis 1985;Denk & Bouchal 2021a, 2021b and references therein). The successions have been dated to 15-17 million years (Rasmussen et al 2010), equivalent to the Miocene Climatic Optimum.…”