North-Central Europe

(Axelrod 1983b ; Butzer 1971; Ferguson 1971; Frenzel 1968; Hammen et al. 1971; Mädler 1939; Szafer 1966)

North-central Europe had a wonderfully rich Neogene forest flora of both conifers and broadleaf hardwoods. Listing of genera (Table 4) understates the richness because many genera were represented by multiple species. Nearly all these genera are considered members of the Arcto-Tertiary Geoflora, which was shared among all the northern continents. Where its members originated and their directions of migration are not known. Very few of them appear to be capable of ocean crossings. A few probably had been shared between Europe and eastern North America before formation of the North Atlantic Ocean in the Paleogene. Exchanges between Europe and Asia may have occurred repeatedly during both Paleogene and Neogene.

Various floras from Poland, Germany, and the Netherlands, from which Table 4 is compiled, suggest that this rich forest flora persisted into the early Pliocene, when it was decimated during the Villafranchian, a time with predominantly heath vegetation. Reforestation occurred during the succeeding warmer Tegelen period, but few tree species returned, although the high alpine barrier to migration did not yet exist. In the Netherlands, about 80% of the species present in the rich early Pliocene Reuverian flora but only about 20% of the species in the impoverished late Pliocene Tegelen flora are now extinct in the region. The late Pliocene Ludhamian flora of Britain was dominated by genera still common there, for example, Pinus, Alnus, Betula, and Quercus ; it had only a few genera that have since become extinct in the region, for example, Tsuga and Pterocarya . Thus, the so-called modernization of the European flora by regional extinction, although not completed until the Pleistocene, was well underway during the Pliocene. Most of the extinct species or close relatives survive elsewhere; for example, North America has living counterparts of the fossil European Pinus (strobus) and Populus (balsamifera) and eastern Asia has living counterparts of fossil Acer (palmatum) and Quercus (serrata) .

Freshwater aquatic species may have suffered less Pliocene and later extinctions in north-central Europe than forest trees did. Szafer (1946) reported

early Pliocene fossils in Poland of 23 species of freshwater aquatic and marsh plants. One water lily, a species of Euryale, is now extinct in Europe and survives only in eastern Asia. All the other species belong to genera that survive in the region, for example, Ceratophyllum, Najas, Sagittaria, Trapa, Carex, and Polygonum ; Szafer assigned 16 of these fossils to living northern European species.