Mid-Miocene floristic changes and differentiation patterns

The Cainozoic period (the past 65 million years) is characterized by a gradual cooling in the Northern Hemisphere culminating in the Pleistocene glaciations. This steady cooling process is interrupted by two marked warming events. One in the Paleocene/Eocene at around 55 Ma, another during the Middle Miocene at around 17- 15 Ma (the Mid-Miocene Climatic Optimum, MMCO). After the MMCO, temperatures steadily dropped towards the Pleistocene period. This climatic signal is based on averaged global deep-sea oxygen isotope records. The aim of this project is to establish regional patterns and timing of floristic, vegetational, and climatic change in the Northern Hemisphere across the period 17-15 Ma to 12 Ma, i.e. from MMCO conditions to post-MMCO conditions. Evidence from previous research using evidence from macrofossils and palynological data from well dated floras from Iceland suggested that the regional (northern North Atlantic) climate signal does not correspond to the globally averaged marine signals. The proposed project is therefore designed to cover representative parts of the Northern Hemisphere, taking into account high, middle, and low latitude floras from North America, Europe, and Asia, in order to evaluate spatial terrestrial climate signals in comparison to the marine isotopic record. Selected pairs of reliably dated (absolute age / biostratigrapy) Miocene plant localities representing the time periods 17-15 Ma and 12 Ma, respectively, will be investigated. Shifts in taxonomic composition from MMCO floras to post-MMCO floras will be recorded, and based on this, a comparative study of floristic turnovers, detecting possible refugial areas and extinction events, will be undertaken. Another goal is tracing differentiation patterns across this period in selected plant groups based on comparative morphological and systematic studies and using phylogenetic frameworks from living taxa. Questions such as whether or not taxonomic radiation or geographic isolation (vicariance) occurred across this time span will be addressed. Finally, plotting the mode of terrestrial climate evolution across the MMCO for realms of the Northern Hemisphere will be use to establish where and in which way terrestrial climate deviates from globally averaged marine climate.