KEY PERIODS IN THE EVOLUTION OF THE FLORA AND VEGETATION IN WESTERN TASMANIA .1. THE EARLY-MIDDLE PLEISTOCENE

The relatively simple flora and structure of Nothofagus cunninghamii c ool temperate rainforest in Tasmania is widely accepted to be the resu lt of repeated glaciation during the Pleistocene. Plant macrofossils, spores and pollen preserved at Regatta Point, western Tasmania, indica te that several gymnosperms and subcanopy angiosperms with warm temper ate affinities had survived one to several episodes of cold, possibly glacial climates, before becoming extinct in the early to middle Pleis tocene: Callitris/Actinostrobus, Dacrycarpus, Austromyrtus, Eucalyptus spathulata-type, Haloragodendron-type, Loranthaceae, Quintinia and Sy mplocos. These co-existed in Nothofagus-Lagarostroboss franklinii rain forest with a number of taxa that are now restricted to upper subalpin e-alpine habitats in Tasmania, such as Astelia, Gunnera and Microcachr ys. The community is difficult to interpret in terms of modem species and we propose that either extinct taxa are being concealed by essenti ally modern pollen morphologies, that ecological preferences have alte red since the early-middle Pleistocene, or both. Patterns of extinctio ns in Tasmania (and New Zealand) suggest that Pleistocene climatic cha nge at middle-high latitudes presented an environmental stress not pre viously experienced during the Cenozoic, perhaps through widespread pe riglacial conditions, but also provided ecological and evolutionary op portunities for rainforest species tolerant of a wide range of conditi ons experienced during the late Pleistocene.