CONICET | Buscador de Institutos y Recursos Humanos

The breakup of Gondwana and the associated climatic changes led to the fragmentation offloras that were once connected across the Southern lands. The diversity of the Gondwananremnants has long been assumed to have fluctuated in Patagonia across the Cenozoic,although it has never been quantified so far. Here we address when the major floristicmembers of the Gondwanan legacy (e.g., southern beeches, proteas, podocarps, gumtrees)expanded, contracted or became extinct during the Patagonian biogeographic isolation(Eocene ? Miocene) on the basis of the re-assessment of the fossil record (i.e., woods, leaves,and spore-pollen grains). We found that the Patagonian floras experienced moderate to severeshifts in diversity of the Gondwanan component ?relative to the total flora? with thehighest estimates in the late Eocene ? early Oligocene (~50%) and the lowest estimates in thelate Miocene (~20%) according to the fossil pollen record. The most important floristicchanges include two major replacements: 1) tropical Gondwanan taxa (e.g., Akania,Eucalyptus, Gymnostoma) by typically cool-temperate taxa (e.g., Nothofagaceae) in theEocene, and 2) humid taxa (e.g., Podocarpaceae) by arid-adapted floras, mostly of non-Gondwanan affinity, across the Miocene. The variation in diversity of the Gondwanancomponent from Patagonia shows a striking resemblance to that from Australia for the sameperiod, probably indicating a global-scale driver of floristic turnover (e.g., global coolingconditions). Today, the Patagonian subantarctic forests harbor only about ~15% of theGondwanan diversity, representing a three-fold decrease from its climax in the late Eocene ?early Oligocene

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