Late persistence and deterministic extinction of “humid thermophilous plant taxa of East Asian affinity” (HUTEA) in southern Europe

Several terrestrial plant fossils found in the late Cenozoic of Europe belong to thermophilous genera or infrageneric taxa which do not grow in this continent today, and are usually called “exotic elements”. Within this large group we singled out three more precisely defined categories based on the hypothesis that the change of geographic distribution between the late Cenozoic and the present is the result of deterministic extinctions caused by climate change. Among the taxa shared by the modern East Asian and the Plio–Pleistocene European flora, the “humid thermophilous taxa of East Asian affinity” (HUTEA) represent the central category in our study. These were traditionally considered “Pliocene” elements in Europe. In our analysis of 13 reliably dated Italian assemblages the percentage of species belonging to the HUTEA category was found to be higher in Pliocene sites, and very low to null in Pleistocene ones. Also early Pleistocene assemblages across all of Europe did not contain any HUTEA, apart from Eucommia, and Symplocos sect. Lodhra in the refugial area of the Colchis.