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Faster, stronger, longer: accelerated evolutionary change in the cane toad


16 February 2006

The relentless march of the toad now means that they have expanded their range to encompass more than a million square kilometres of tropical and sub-tropical Australia and have even reached as far as northern NSW
The relentless march of the toad now means that they have expanded their range to encompass more than a million square kilometres of tropical and sub-tropical Australia and have even reached as far as northern NSW

The accelerated evolution of invasion species looks set to turn a disaster into an ecological nightmare, according to research undertaken by Professor Rick Shine from the University’s School of Biological Science.

Published yesterday in scientific journal Nature the brief paper entitled Invasion and the evolution of speed in toads shows that the annual rate of progress of the cane toad invasion has increased five fold since their introduction into Queensland in 1935. Toads expanded their range by about 10km a year during the 1940s to 60s, but are now invading new areas at a rate of over 50km a year

By attaching radio transmitters to the toads, Professor Shine and his team found that toads with longer legs not only move faster and are the first to arrive in new areas, but also that those at the front have longer legs than those in older (long-established) populations. They also found that these long-legged toads had more endurance, travelling about half a kilometre further in a three day period.

‘When an invasive species is first introduced, the population remains low for a few generations before exploding,’ Professor Shine said. ‘It’s likely that such lags reflect, at least in part, adaptive changes in the invader to suit it to the new environment.’

Cane toads (Bufo Marinus) were introduced to Australia 70 years ago to control insect pests in sugar-cane fields with disastrous results due to their toxicity which proves fatal for many of Australia’s native predatory species including snakes, lizards and mammals. The relentless march of the toad now means that they have expanded their range to encompass more than a million square kilometres of tropical and sub-tropical Australia and have even reached as far as northern NSW.

‘These findings indicate that evolutionary forces are likely to fine-tune organism traits in ways that facilitate more rapid expansion of the invading population. Hence, control efforts against feral organisms should be launched as soon as possible, before that invader has time to evolve into a more dangerous adversary,’ warns Professor Shine.


Professor Shine's Sydney team of researchers also included Ben Phillips, Greg Brown and Jon Webb


 


Contact: Jake O'Shaughnessy

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