South Australian researchers will lead an international study into whether fleas and ticks are creating new subspecies of sleepy lizards.
- Parasites are a major selective force in host evolution
- Fleas and ticks could be creating new species of sleepy lizards
- Parasites might be impacting the ability shinglebacks have of recognising each other
Fleas, ticks and other parasites live on sleepy lizards — also known as shinglebacks — and other lizards.
The international study, led by Flinders University in South Australia, will be conducted two hours north of Adelaide, between Burra and Morgan, where the environment consists of both Mallee scrub and grassland.
This location was chosen because it is where lizards with different parasites interact with one another.
“Parasites represent a major selective force in host evolution,” said lead researcher, Associate Professor Mike Gardner.
He said parasites could alter their hosts’ immune gene — which was what they use to fend off diseases.
“The parasite type in a geographic area might cause the lizards there to all have the particular form of that gene that has the ability to resist the parasite,” Professor Gardner said.
The study will be looking at how parasites cause host divergence, which is when one species becomes two.
Professor Gardner said the immune gene was how sleepy lizards recognised each other and if the parasites caused a change in that gene, it would make it difficult for the lizards to recognise one another.
“If the parasites’ ability to cause differences in the lizards’ genes is really strong, then maybe lizards with different parasites will stop recognising them [lizards] as being the same species,” he said.
One species becomes two
Sub-species can sometimes occur when a physical barrier is put up, making it difficult for one group of sleepy lizards to interact with another.
But Professor Gardner said it was also possible for that to happen without a physical barrier.
“It can occur through other measures such as parasites,” he said.
“The selection pressures that are occurring in the host sleepy lizard on either side of that barrier may actually be driving some level of host divergence where individuals on either side are unable to recognise each other.”
The study will investigate whether parasites can act as a similar barrier.
“It all comes back to the parasites evolving ways to attack their hosts and the lizards evolving ways to defend against those parasites,” he said.
While sleepy lizards commonly interact with one another, they are monogamous when mating, meaning they only have one partner.
“Males and females come together for three months of the year during the breeding season and then move about in the landscape and encounter other individuals,” said Martin Whiting, an Associate Professor in animal behaviour at Macquarie University.
He said sleepy lizards were well suited for the type of research in SA, because they interacted with each other.
“Understanding how the social system might be driven by the types of parasites that they’re dealing with is a really interesting question,” he said.
The effect of climate change
Professor Gardner said the research would also look at whether or not climate change was affecting where the parasites called home.
“If parasites are going to change their ranges according to the changing climate, they’re going to come into contact with different hosts than they would normally,” he said.
“So, that may affect how the species reacts to the parasites; it may affect how those interactions occur.”