Recent evidence for authochthony of Australian tropical and subtropical rainforest floristic elements. Telopea 2(6): 575-589 -Studies in continental drift suggest that much of the Australian flora is of Gondwanic origin. The fossil record shows so-called 'Indo-Malesian' and 'Antarctic' elements of the Australian flora were present in southern Australia before a land bridge with South-East Asia was possible, and before Australia and Antarctica were separated. Today there is a remarkable concentration and variety of families of primitive angiosperms in the rainforests of north-eastern Australia; many taxa of which are of low vagility. A recent floristic classification of Australian rainforests revealed certain patterns of outliers and disjunct and relict species assemblages interpretable by past environmental sifting. The existence of refugia of great antiquity is postulated under certain ecological conditions. The proportion of tree genera, often of low vagility, shared between homologous habitats in Australia and the Indo-Malesian region suggests common !mcestry. Interspersion of rainforest and sclerophyll floras supports the theory that rainforest elements are authochthonous and archetypal, and sclerophyJls largely derivative. This contrasts with traditional phytogeographic interpretations. The use of the terms 'Indo-Malesian' and 'Antarctic' to indicate sources of intrusive floral hnmigrants should accordingly be discontinued. Thus tropical or megatherm rainforest and monsoon forest floristic elements should be added to the subtropical (mesotherm) ~nd temperate (microtherm) elements already recognized as remnants of the ancient Gondwanan flora that once covered Australia.
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Webb et al. (1986) studied this question.