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(Dr. Leo Joseph) Australia's biodiversity is in a large part
so distinctive because of the isolation of
the continent on geological time scales.
That means that the fauna and flora, the biota of Australia,
have been able to evolve in isolation from the rest of the world.
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.
So if we think a little bit more about the isolation of
Australian 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.
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.
It's not that simple; organisms can move; dispersal is very real thing.
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.
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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.
What we today know of as Australia and the island of New Guinea,
were connected up in one land mass known as Sahul.
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.
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.
So we have the magnificent Bird of Paradise,
and in my left that I'm raising now is a New Guinean specimen.
And in my right hand, raising now, is a specimen from North Queensland.
So it's an example of pretty close similarities, that you can see close
relationship between Australia and New Guinea.
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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.
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.
This resulted in wetter habitats like rainforests
and temperature forests becoming restricted to the
fringes of the continent. 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. So after they've been burnt you'll see leaves
and small branches sprouting directly from the trunk of the tree.
This is called epicormic growth and it's a response to being burnt.
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.
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The technology with which we can study Australia's biodiversity,
or indeed the biodiversity of any region, is always changing.
And one of the biggest changes has been the advent of being able to get
to DNA sequences. 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.
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.
We study the Australian fauna and flora at CSIRO,
and with colleagues from all around the world
at different museums and universities.
We are all using the information in DNA sequences
to better understand diversity that's out there.
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