Originating in temperate (frost-free) biomes, Eocene to Oligocene ranges of the primarily deciduous cork oaks were restricted to higher latitudes (Siberia to north of Paratethys). Members of the evergreen holly oaks (sect. Ilex) also originated in temperate biomes but migrated south- and south-westwards into then-(sub)tropical southern China and south-eastern Tibet during the Eocene, then westwards along existing pre-Himalayan mountain ranges. Divergent biogeographic histories and deep-time phylogenetic legacies-in cold and drought tolerance, nutrient storage, and fire resistance-thus account for the modern species mosaic of Western Eurasian oak communities, which comprise oaks belonging to four sections.