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Insights into the origin of a Mediterranean biodiversity hotspot based on palynological and biomarker analyses of Lake Ohrid sediments from Early Pleistocene (> 1.2 Ma)


Our current knowledge about Early Pleistocene climate and flora in the Mediterranean region is based mostly on fragmentary terrestrial archives complemented by marine cores. In an effort to improve our understanding of the climate and flora evolution over this interval, a new 569m-long core was retrieved in 2013 within the frame of the ICDP drilling at Lake Ohrid. Preliminary analyses show continuous sedimentation over the last ~1.2 million years and indicate major shifts in organic carbon, pollen and diatom assemblages corresponding to the characteristic marine isotope stage (MIS) stratigraphy. Considering the reduced global ice volume and shorter climatic cycles paced by obliquity observed in marine cores during this period, the research objectives of this new ICDP project are: (i) the determination of the floristic diversity in a southern refugium during the formation of Lake Ohrid and prior to the onset of the Mid-Pleistocene transition with a focus on relict subtropical species, (ii) the reconstruction of environmental and hydrological history of Lake Ohrid, (iii) the identification of the main drivers of terrestrial and aquatic ecosystem change in the Ohrid Basin since the formation of the lake until MIS 35 under an obliquity-controlled climate regime (41-kyr cycles), and (iv) the quantitative reconstruction and assessment of the nature and amplitude of climate variability during this interval in the Eastern Mediterranean region.