Sydney Morninng Herald, 4/27/17 by Amy Mitchell Whittington
Water
dragons living in separate parks across Brisbane have evolved
differently from one another in a process likened to the Galapagos
Islands evolution recorded by Charles Darwin, a Queensland researcher
says.
The
first "clue" was a DNA variation across 570 eastern water dragons at
South Bank, Roma Street Parkland, the City Botanic Gardens and Mt
Coot-tha Botanic Gardens monitored by University of Sunshine Coast
Senior Research Fellow Dr Celine Frere.
"That
was the first clue to tell us there was something going on in the city
that was not your conventional type of evolution," Dr Frere said.
Studies revealed there were also physical differences between each population that lived within kilometres of each other.
The
study, published in the journal Molecular Ecology, found males varied
in overall size, while females varied in terms of head and leg size, Dr
Frere said.
"The
animals at the city botanical gardens, they are by far the largest
animals and they seem to have, in relation to body size, shorter limb
length than other parts," she said.
"In contrast, the animals we found at Mount Coot-tha botanical garden are smaller in size but they have longer back limbs.
"At
Roma Street Parkland the animals are quite small but they have larger
heads and shorter limbs whereas the animals at South Bank are also
fairly small but they have smaller heads and longer limbs.”
While
Dr Frere did not know why this species had evolved so differently in a
short time – over 32 generations in "lizard time" or since the city's
development in the mid to late 1800s – she suggested landscape and
microhabitat variations were likely factors.
"The
simplest explanation is to think of each city park as being quite a
unique ecosystem and different to one another," she said.
"Each
of these city parks are different ecosystems, are geographically
isolated ... we could look at city parks as islands in a jungle of
concrete that make up this archipelago that has similar evolutionary
processes like the Galapagos."
Dr
Frere said the heaviest male caught during the study, from the City
Botanic Gardens, weighed 1.4 kilograms, almost double that of males
caught in native habitats.
"This
is a common thread when you study island evolution: they say
(gigantism) is a biological phenomenon where the size of an animal when
isolated on an island increases dramatically compared to its mainland
relative," she said.
Dr
Frere said the staggered process by which the parks were developed – Mt
Coot-tha opened in the 1970s while South Bank opened in the
1980s – could have also influenced the variation.
"Anthropogenic
pressures, while they do extensive damage to biodiversity, they are
recognised as one of the more significant selective pressures that
results in rapid evolution," she said.
"We
talk about this idea that cities may be representing these theatres for
rapid evolution because animals that do live within cities have to
drastically change their way of life.”
So what is the next step in this evolutionary expedition?
"We
are going to study the ecology of these parks in much more detail, the
thermal landscape and the 3D landscape ... looking also at the
biodiversity composition in terms of diet and how these animals are
negotiating these landscapes by GPS tracking them and looking at their
fine-scale movements across a few days," she said.
"We
often thought of this as an urban versus non-urban dichotomy … but here
it is to show we go even deeper than that, it is every dragon within
every city park (being) extremely different to other dragons in another
city park."
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