Read all about it at NatGeo. Here's an excerpt:
When studying infant lizard populations, Langkilde noticed that longer hind limbs are more prevalent at birth in lizards from fire-ant exposed populations, indicating an evolutionary adaptation—not a response to habitat as seen in some lizard species, she noted.
Longer leg length was likely genetically selected because it gives the lizards more leverage to shake off the ants and flee more quickly, said Langkilde, whose study appears in the January issue of the journal Ecology.
Langkilde also tried to determine whether the skittish behavior is a learned or evolved response.
If the twitch-and-flee behaviors were learned, she figured lizard young would not respond at fire-ant-free sites. If the behaviors were evolved, then only babies from the invaded sites would respond.
"Of course, science being science, you never find what you expect and we found all the babies responded all the time," Langkilde said.
It may be that all juvenile lizards respond to the ants because any ants pose a threat to them.
For example, lizards in non-affected sites appear to stop the skittish response once they mature because their adult scales provide sufficient protection.
In addition, twitching and fleeing could alert the otherwise well-camouflaged brown lizards to other predators.
Where fire ants have moved in, however, only the lizards that maintain the twitch-and-flee behavior into adulthood have survived, and thus passed on their genes, Langkilde speculates.