City living comes with unique challenges. If youâre a lizard, scaling a windowpane without sliding off is one of them. One lizard has already evolved traits to help it do just that.
âUrban areas are just another environment. The animals that live there arenât somehow immune to natural selection,â says of the University of Massachusetts Boston.
Her team compared males of the anole lizard (Anolis cristatellus) in the Puerto Rican cities of MayagĂźez, Ponce and San Juan with those in nearby forests.
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They found that city lizards regularly clung to objects like walls and windows, proving that they use the full urban environment instead of restricting themselves to wild patches more similar to their forest roots.
Compared with forest-dwellers, city lizards had longer limbs and more lamellae â scale-like structures that help their toes stick to surfaces. These traits probably enable them to stay attached to slippery urban perches. âI chased a lizard that ran straight up a window 30 feet and was out of reach in 15 seconds,â says Winchell. âI couldnât catch this well-adapted lizard.â
The team also raised urban and forest lizards from the MayagĂźez region in the lab and found that differences in limb length and scale number remained, suggesting a genetic basis to the urban lizardsâ abilities.
The anole frequently wows scientists with feats of rapid evolution in natural environments. The new finding suggests that this capacity applies to cities as well.
Other urban animals also adapt. We know, for example, that birds alter calls to be heard over city noise and in an urban heat island.
But well-studied examples are rare. âUrban evolution is a really young field,â says Winchell.
Evolutionary biologist of Fordham University in New York agrees. âThere arenât many documented cases of urban evolution yet, but people are going to start looking for them in earnest,â he says.
Munshi-South believes Winchellâs study is an excellent addition to this emerging field. âThe next step,â he says, âwhich Iâm excited to see them do, is to identify the genes underlying these adaptive traits.â
Winchell says that, ultimately, understanding urban adaption could help conservation. âHaving a grasp on which animals tolerate urbanisation gives us a better idea of which ones we need to focus on when preserving natural habitats,â she says.
Evolution
