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A new tree - of our most iconic trees

Phylogenies (family trees indicating likely evolutionary relationships between species and other taxa) are important tools of modern taxonomy and biosystematics.

Andrew Thornhill from CSIRO's Australian National Herbarium in Canberra and colleagues have published the most recent and detailed phylogeny of the eucalypts. Andrew has also summarised his research in an article in The Conversation.

Eucalypts (bloodwoods, angophoras, a group of closely related tropical eucalypt genera, and of course the large genus Eucalyptus) are almost quintessentially Australian. A few species occur in southern Papua New Guinea and Indonesia, while one related genus occurs in New Caledonia, but nowhere else on Earth do eucalypts dominate as they do here.

Salmon Gums (Eucalyptus salmonophloia) at Credo, Western Australia. Photo (c) Suzanne Prober

However, this has not always been the case. Eucalypt fossils have been found in South America and New Zealand, areas that are devoid of native eucalypts now. And results from this study indicates that for much of Australia's history as an independent continent, eucalypts probably did not dominate as they now do. In fact, many eucalypt species are surprisingly young, following a burst of evolution in the genus only 2 million years ago.

There is still a long way to go in our understanding of eucalypt phylogeny. Many recent studies give conflicting results or are ambiguous in their relationships, and this paper acknowledges areas of weakness and uncertainty. A much more robust and stable phylogeny is needed - hopefully this will be provided soon.

We will then be able to explore the evolutionary history of our iconic eucalypts, and through them the evolutionary prehistory of Australia.

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