Key Periods in the Evolution of the Flora and Vegetation in Western Tasmania .I. The Early-Middle Pleistocene

Abstract

The relatively simple flora and structure of Nothofagus cunninghamii cool temperate rainforest in Tasmania is widely accepted to be the result of repeated glaciation during the Pleistocene. Plant macrofossils, spores and pollen preserved at Regatta Point, western Tasmania, indicate that several gymnosperms and subcanopy angiosperms with warm temperate affinities had survived one to several episodes of cold, possibly glacial climates, before becoming extinct in the early to middle Pleistocene: Callitris/Actinostrobus, Dacrycarpus, Austromyrtus, Eucalyptus spathulata-type, Haloragodendron-type, Loranthaceae, Quintinia and Symplocos. These co-existed in Nothofagus-Lagarostroboss franklinii rainforest with a number of taxa that are now restricted to upper subalpine-alpine habitats in Tasmania, such as Astelia, Gunnera and Microcachrys. The community is difficult to interpret in terms of modem species and we propose that either extinct taxa are being concealed by essentially modern pollen morphologies, that ecological preferences have altered since the early-middle Pleistocene, or both. Patterns of extinctions in Tasmania (and New Zealand) suggest that Pleistocene climatic change at middle-high latitudes presented an environmental stress not previously experienced during the Cenozoic, perhaps through widespread periglacial conditions, but also provided ecological and evolutionary opportunities for rainforest species tolerant of a wide range of conditions experienced during the late Pleistocene.