Friday, 23 March 2012

What makes a ground-dwelling and disease-carrying tick decide to crawl up a grass stalk and launch itself onto a human or animal host?

Are some solitary locusts more likely than others to suddenly band together in plague proportions and act as one?

And why do single-celled algae change from vegetative reproduction to having sex?

These and other questions are being investigated by evolutionary biologist Future Fellow Professor Joseph Tomkins in the Centre for Evolutionary Biology.

He is testing a model that seeks to explain what triggers changes in the behaviour or development of living things, whether they are as small as single cells or as big as a plague of insects, numbering many millions.

The model, pioneered by Professor Tomkins's collaborator, Professor Wade Hazel at De Pauw University in the United States, suggests that a certain threshold in the environmental conditions experienced by an organism make it switch between two alternatives.

"A cell can divide itself or find another cell to exchange DNA with, as it divides," Professor Tomkins said. "A male salmon might stay in its home river growing to only a few hundred grams, or go to sea for years, returning weighing a few kilograms. The model we are interested in treats the decisions that organisms make as traits, and asks how these decisions evolve. To date it has not been applied to the breadth of questions to which it could."

Professor Tomkins, who won an Australian Research Council Future Fellowship of almost $1million over four years, will travel to France and Scotland to examine the behaviour of deer ticks, which are responsible for the growing spread of Lyme disease throughout parts of Europe.

"The tick that carries Lyme disease - which can be extremely disabling, and even fatal, if not treated with antibiotics - climbs up a grass stalk to look for a host only in certain weather conditions," he said. "By knowing what triggers its behaviour, we hope to be able to warn farmers to move their stock, and hikers to avoid tick-infested areas, at times when ticks are searching for hosts."

Lyme disease also occurs in Australia, causing at least one death in the past 18 months.

"My ARC project will test the environmental threshold model to see how well it applies to decision-making in a range of organisms across the spectrum of life.

"It will help us understand the diversity of life and give us insight into what happens when species are under threat from human activity," he said.

Published in UWA News , 19 March 2012


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