'Runaway' Evolution Spreading Toads

TOWNSVILLE, Australia, Oct. 20 (UPI) — A runaway evolutionary effect is accelerating the spread in Australia of the invasive cane toad species, scientists say.

Researchers say toads living at the very edge of their range have evolved into “super-invaders” able to move beyond the boundaries of their existing habitat, the BBC reported Wednesday.

And when toads at those frontiers breed, researchers say, their offspring are inheriting this capability of moving into new territory.

Scientists have observed that toads at the edge of the range had bigger front legs and stronger back legs, equipping them to more effectively jump into and invade new areas.

To confirm this increased strength and speed had a genetic basis and could be inherited, researchers studied the next generation.

Toads that had parents from the frontiers of their range proved to be stronger and faster than offspring of frogs inhabiting the central region of their range, showing the traits had been passed on.

“It’s bad news,” one researcher said. “It means they’re getting faster and better at invading new areas.”

Even worse, Ben Phillips from James Cook University in Queensland says, all animal invasions are likely to follow this pattern.

Cane toads were introduced to north tropical Queensland in Australia in 1935 to control sugar cane pests.

They failed to do this, but managed to become one of the International Union for the Conservation of Nature’s top 100 invasive species.

“They’re certainly up there with the worst invasive species,” Phillips says. “They’re doing well for themselves, you have to give them that.”

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