A team of researchers including South Australian Museum bioinformatics specialist Terry Bertozzi has discovered a remarkable incidence of convergent evolution in skinks battling highly-venomous snakes in an evolutionary arms race.
Resistance to the venom of Australian elapid snakes including death adders, tiger snakes and brown snakes has risen independently at least 25 times in separate species of skinks, which are small lizards.
The skinks have developed the same forms of venom resistance found in many other animals from around the world including the honey badger, which preys on cobras and lives throughout Africa, the Middle East and India.
Dr Bertozzi said convergent evolution occurs when unrelated species evolve similar traits independently, often due to similar environmental pressures or ecological circumstances.
“Convergent evolution is quite common in nature,” Dr Bertozzi said.
“It occurs across many groups of organisms - from animals and plants to fungi and even microbes - whenever different species face similar environmental or functional challenges.”
The snakes use a neurotoxin in their venom that blocks muscle receptors usually used to control normal muscle function. Affected muscles can no-longer contract leading to paralysis, respiratory failure and death.
The skinks have developed three different types of protective mutation to the receptor:
· physically block the neurotoxin with proteins;
· change the structure and shape of the receptor;
· change the electrostatic charge of the receptor to reject the positively charged neurotoxins.
Many species of skinks have developed more than one of the strategies in the 24 million years since elapid snakes first arrived in Australia.
Importantly, the mutations can’t interfere with normal muscle function which is activated through the receptor.
Dr Bertozzi said the adaptions had been widely explored by researchers in other animals around the world that prey on and are preyed upon by snakes. But this was the first study in skinks, which live in a particularly snake-hostile environment.
“Skinks are the most species-rich group of lizards in Australia and occupy nearly every habitat, from deserts and forests to grasslands and coastal areas,” Dr Bertozzi said.
“This study highlights one adaptation that has contributed to their success.”
The paper appeared in the International Journal of Molecular Sciences, and was led by the Adaptive Biotoxicology Lab of the University of Queensland.
The team pointed out the study provided valuable insights that could inform fields as diverse as evolutionary biology, ecology, and even the treatment of snakebite in people.
“In essence, the evolution of extensive venom resistance in Australian skinks stands as a testament to nature’s ingenuity,” the team said in the paper.
“Faced with the threat of rapid, venom-induced paralysis, these little reptiles evolved molecular armour at the synapse.
“If a skink species can survive in areas teeming with deadly snakes, it might exploit resources (food, habitat) that other reptiles or rodents who lack such resistance cannot, potentially reducing competition.
“This could partly explain the success and abundance of certain skink lineages in Australia’s harsh, predator-rich environments.”
You can read the paper here.
