Origins of the southeastern Australian vegetation

Abstract

Australia is an ancient continent with an interesting geological history that includes a recent major shift in its position, both globally and compared with neighbouring land masses. This has led to a great deal of confusion over many years about the origins of the Australian biomes. The plant fossil record is now clarifying this, and it is clear that the ancient Gondwanan rainforests that covered Australia while it was still part of that supercontinent contained many of the elements of the modern vegetation. However, major climatic sifting, along with responses to other factors, including soil nutrient levels, disturbance regimes, atmospheric CO 2 levels, fire frequency and intensity, glaciations and the arrival of humans, have had profound impacts on the Australian vegetation, which today reflects the sum of all these factors and more. The origins of Australian vegetation and its present-day management cannot be properly understood without an appreciation of this vast history, and the fossil record has a vital role to play in maintaining the health of this continent's vegetation into the future.

Origin, Diversification, and Classification of the Australasian Genus Dracophyllum (Richeeae, Ericaceae)1

“…The southern continents were united, forming the supercontinent Gondwana, but began to drift apart during the Late Cretaceous. Because of their position in high latitudes, there were three months of complete darkness in winter followed by nearly continuous daylight during the brief summer (Hill, 2004;McGlone, 2006). The forest vegetation was dominated by diverse angiosperms, podocarps, araucarias, and ferns.…”

“…We rooted our phylogeny on the long branch leading to Enkianthus and set the minimum age of this branch at 90 Ma, which reflects the first appearance of allied fossils during the Late Cretaceous (Nixon & Crepet, 1993). The environmental conditions that existed during the early evolution of the Ericaceae were dramatically different from those of the present day (Raven & Axelrod, 1972;McLoughlin, 2001;Hill, 2004;Hopper & Gioia, 2004;Gibbs, 2006;McGlone, 2006;Ladiges & Cantrill, 2007). The southern continents were united, forming the supercontinent Gondwana, but began to drift apart during the Late Cretaceous.…”

Introduction and synthesis: plant phylogeny and the origin of major biomes

“…In the cases of Africa (Jacobs 2004), the Neotropics (Burnham & Johnson 2004) and Australia (Hill 2004), there are palaeontological reviews. These are essential for two reasons.…”

“…Australia is particularly interesting in this context because it is an ancient and discrete landmass, isolated from other continents since 25 Myr ago. Hill (2004) traces a Gondwanan element in present-day biomes, particularly in the gymnosperms. However, this element has been much influenced by in situ evolution, apparently driven by Australia's massive postGondwanan environmental shifts.…”

“…However, this element has been much influenced by in situ evolution, apparently driven by Australia's massive postGondwanan environmental shifts. Whereas Hill (2004) uses palaeobotany to look forward in time to present-day biomes, Crisp et al (2004) extrapolate historical patterns through the collation and examination of numerous phylogenetic analyses. They note that lineages in different biomes have different histories, and many appear to have a post-Gondwanan origin in Australia.…”