Chapter 2. Australia's biodiversity: major features

This chapter discusses the major factors that have shaped Australia's unique biodiversity and how new technologies are revealing some surprises in the evolutionary story.

Australia's biodiversity: major features: Watch an interview with author Dr Leo Joseph (06:01)

Show transcript

[Music plays and text appears: Australia’s biodiversity – Major features]

[Image changes to show Dr. Leo Joseph – Evolutionary Biologist]

Dr. Leo Joseph: Australia’s biodiversity is in a large part so distinctive because of the isolation of the continent on geological time scales.

[Image changes to picture of kangaroos]

That means that the fauna and flora, the biota of Australia, have been able to evolve in isolation from the rest of the world.

[Image changes to a picture of a platypus]

[Image changes to a picture of a cassowary]

[Image changes to a picture of a koala]

But against that one shouldn’t forget that from time to time the continent has received species from areas to the north, especially from South East Asia.

[Images changes to a picture of a dingo]

[Image has changed back to Dr. Leo Joseph]

So if we think a little bit more about the isolation of Australia and why the biota is so distinctive, we get back to thinking about the Gondwanan supercontinent that comprised present day South America, Antarctica, Australia, New Zealand, and Africa.

[Image changes to a river landscape]

[Image changes to picture of Gondawana supercontinent]

[Image changes to varying stages of Australian continent]

And as that supercontinent broke up the resulting continents that we have today were a lot like rafts, and as they drifted their fauna and flora were able to evolve in isolation.

[Images changes to a parrot in a tree]

It’s not that simple; organisms can move; dispersal is very real thing.

[Images changes to show Dr. Leo Joseph observing bird specimens in a drawer]

[Image has changed back to Dr. Leo Joseph]

And so a lot of the research that we can do today on the fauna and flora of a continent like Australia is aimed at teasing apart the role of rafting on a continent, or dispersal from other areas.

[Text appears: The role of sea level rise and fall]

[Image has changed back to Dr. Leo Joseph]

Not so long ago in the geological and evolutionary scheme of things, that the... what’s called the last glacial maximum, around about 20,000 years ago, when a lot of water was tied up in the polar icecaps, sea level was much lower and the shoreline of Australia extended much further out than it does now.

[Image changes to icebergs floating in the ocean]

[Images changes to a satellite image of Australia]

What we today know of as Australia and the island of New Guinea, were connected up in one land mass known as Sahul.

[Image changes to map of Sahul]

[Image has changed back to Dr. Leo Joseph]

We can read today, when we do our research on the genetic structure and the genetic makeup of present day species, we can look for and read the genetic signature of how populations were... could have been connected between Australia and New Guinea.

[Images changes to show Dr. Leo Joseph observing bird specimens in a drawer]

[Image has changed back to Dr. Leo Joseph]

Some species and some groups show this connection really quite readily, and the Birds of Paradise are an example. Most of the spectacular and stunning Birds of Paradise occur in and around New Guinea, but Australia has a few species, and this is an... these two are an example of something that is I think still classified as the same species.

[Image changes to a close up view of Birds of Paradise held by Dr. Leo Joseph]

So we have the magnificent Bird of Paradise, and in my left that I’m raising now is a New Guinean specimen.

[Dr. Leo Joseph holds up the New Guinean Bird of Paradise specimen in his left hand]

And in my right hand, raising now, is a specimen from North Queensland.

[Dr. Leo Joseph holds up the New Guinean Bird of Paradise specimen in his right hand]

So it’s an example of pretty close similarities, that you can see close relationship between Australia and New Guinea.

[Image changes to a picture of a bushfire and text appears: The role of climate and fire]

So climate and fire are two factors that we can think about in terms of how they’ve contributed to shaping and evolving the present day fauna and flora that we have in Australia.

[Image changes to various landscapes showing bushfires]

[Image has changed back to Dr. Leo Joseph]

[Text appears: Miocene]

We know that around about the middle of the period known as the Miocene, so around about 16 to 11, 10 million years ago the Australian continent started to really dry out and lead to the largely arid zone continent we have today.

[Image changes to a map of Australia]

[Image changes to arid landscape]

[Images changes to rainforest landscape]

This resulted in wetter habitats like rainforests and temperature forests becoming restricted to the fringes of the continent.

[Image changes to footage of a bushfire]

Fire was becoming a key element in the Australian environment, and so we see the signs of a lot of plants, for example the habit that many eucalypts have of being able to sprout what’s called epicormic growth form the trunks of trees.

[Image changes to a picture of eucalypt trees and text appears: Epicormic growth]

So after they’ve been burnt you’ll see leaves and small branches sprouting directly from the trunk of the tree.

[Image has changed back to Dr. Leo Joseph]

This is called epicormic growth and it’s a response to being burnt.

[Images changes to picture of Black Cockatoos]

It’s also well known that some birds like Black Cockatoos can best get to the seeds that are in some plants when those plants have had their fruits opened up by the heat of a fire, so you can start to see an interplay between fire and the biota.

[Images changes to a picture of opened seed pod]

[Image changes to a man standing at a machine and text appears: New technologies reveal more of the story]

[Image has changed back to Dr. Leo Joseph]

The technology with which we can study Australia’s biodiversity, or indeed the biodiversity of any region, is always changing.

[Image changes to show a person conducting various tests]

And one of the biggest changes has been the advent of being able to get to DNA sequences.

[Image changes to various pictures of lizards]

Currently the Australian reptile fauna, and even the mammal fauna, is undergoing a bit of a revolution in terms of our knowledge of the species that are out there.

[Image changes to two men observing a lizard]

[Image changes to various animals]

So many of the reptiles that we thought were one species turn into if not several species, then certainly we can see that they are made up of several very deeply divergent evolutionary lineages when we go down to the DNA level.

[Image changes to spreadsheets on a computer]

[Image changes to a man recording observations in the bush]

We study the Australian fauna and flora at CSIRO, and with colleagues from all around the world at different museums and universities.

[Image changes to bird specimens in a drawer]

[Image changes to a man performing a test]

[Image changes to a man standing at a machine]

[Image has changed back to Dr. Leo Joseph]

We are all using the information in DNA sequences to better understand diversity that’s out there.

[Text appears: MUSIC –; ADDITIONAL FOOTAGE – Justin Perry; ADDITIONAL IMAGES – Bruce Webber, Carl Davies, Healesville Sanctuary, Robert Kerton, Murray Fagg, Joe Miller, Creative Commons images (Flickr, Wikimedia): Bill & Mark Bell, David Cook, Sam Fraser-Smith, LennyWikidata.

[Music plays and CSIRO logo appears with text: Big ideas start here]

Hide transcript

Since the break-up of Gondwana, Australia’s biodiversity has evolved mostly in isolation from the rest of the world. Today, it occupies a special place in the world’s natural heritage.

Overview of the chapter

From inland deserts to the rocky walls of marine canyons, Australia’s biomes each have a distinctive complement of fauna and flora. For species on land, fire has been a powerful evolutionary force. In the oceans, Australia boasts one of the most diverse arrays of organisms worldwide.

Many of our iconic species illustrate the power of isolation in evolution and modern DNA analysis is revealing ever more surprises about the evolution of Australian biodiversity.

Download the chapter or the whole book [PDF and EPUB versions available]

Chapter authors

Leo Joseph, David K. Yeates, Joseph Miller, David Spratt, Daniel Gledhill and Alan Butler


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