Evolutive-biogeographic history of the flora of subtropical forests in Central Chile

Abstract

Central Chile exhibits a unique biogeographic combination of Neotropical and Austral-Antarctic floristic components, a mixed character recognized by the distinction of a “Chilean Province” and its status as an interface between two major biotas with Gondwanan roots. Using phylogenetic, phylogeographic, and paleobotanical evidence, we examine the main woody genera of the sclerophyllous forest of Central Chile belonging to these two biogeographic elements, and their differentiation associated with the complex tectonic-climatic factors that occurred during the Cenozoic. The geographic isolation associated with the fragmentation of Gondwana during the Paleogene is illustrated by Drimys, Aextoxicon, and Gayella, and similar cases are discussed. The Neotropical component, differentiated during the Neogene, is exemplified by Myrceugenia, Escallonia, Azara, and Jubaea/Cocoseae, now disjunct with the eastern Andes, and analogous discontinuities are discussed. By the end of the Neogene, through the cases of Archidasyphyllum/Barnadesioideae, Porlieria, and Vasconcellea, the radiation of the xeric Neotropical Element linked to the Andean uplift and development of the Arid Diagonal of South America and the Atacama Desert is considered. The role of Pleistocene climate changes in the distribution of forests in Central Chile is discussed. This period was marked by the expansion of populations of various Austral- Antarctic species, particularly Nothofagus and conifer species, to lower latitudes during the wetter glacial periods. Based on phylogeographic evidence, the fragmentation of sclerophyll and fog communities during the arid periods of the Holocene is described, a process exemplified by Cryptocarya alba, Myrceugenia correifolia, Aextoxicon punctatum, and Drimys winteri.