Puerto Rican urban lizards have adapted in such a way that they are genetically different from their forest counterparts.
A city is usually hotter, noisier and more polluted than the nature around it. And of course full of buildings and people. The animals living in it will have to adapt to this. An urban lizard in Puerto Rico appears to have succeeded. Now it has even developed a different genetic profile than its backwoods counterparts. So they discovered the biologists, led by Kristin Winchell of New York University. They posted about it Proceedings of the National Academy of Sciences.
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Adaptation to city life
The species of lizard Anolis Christatellus it’s small and fast. Males possess a small “dorsal fin” and dewlap which they may wear as part of their mating ritual. The lizard can be found in the forests of Puerto Rico, but has now made its way into the city life of that country as well.
Previous research by Winchell and colleagues has already demonstrated this A. christatellusspecimens in the city have longer legs than those living in the forest. This allows them to run faster in the open spaces between buildings. They also have larger toe caps, making it easier for them to walk on smooth surfaces, like walls and windows. But do these special traits also have a genetic basis?
Difference in genes
The researchers analyzed a total of 96 lizards in the cities of San Juan, Arecibo and Mayagüez and in the surrounding forests. They measured the paws and toes of the animals. Just like in the previous study, these turned out to be larger in forest specimens for urban lizards.
Subsequently, Winchell and his team discovered that the urban A. christatellus had a set of 33 genes that differed from those of forest dwellers. He involved genes involved in limb and skin development. These account for the longer legs and paws. There were also genes required for the immune system, wound healing and metabolism.
Stronger defenses
Winchell and colleagues think these latter genes are also very important to life in a city. A stronger defense helps against vermin, which are more common in cities, and quick healing of wounds is needed because city lizards are more easily injured. Even the food in the city is different from that of the forest and it is good to adjust the metabolism accordingly.
The physical properties we see in the city lizard can therefore actually be seen in the animal’s genes. According to the researchers, this concept may also have predictive value. In this way it could be seen for each animal whether it actually adapts genetically to urban life. If that doesn’t work or doesn’t work quickly enough, then such an animal is susceptible to extinction and you should further protect the species.
Survival of the fittest
“The phenomenon of species adapting to urban environments is not new,” explains animal ecologist Rob Lenders of Radboud University Nijmegen. “Our blackbird is a good example of this; he developed from a shy forest bird to a cosmopolitan city dweller. To my knowledge, the extent to which such adaptations are genetic in nature, as researched herein, is new.
“Nature seems to be able to adapt to our influences relatively quickly,” he continues. “But we shouldn’t overestimate that either. Animal species that are not as flexible or quick to adapt will have great difficulty avoiding extinction.”
“This excellent study provides a good example of the concept survival of the fittest (The best-adapted animals have more offspring, ed.),” says animal pathologist Gerry Dorrestein of the NOIVBD. “The adaptations that city lizards have developed here give a significant advantage in this environment; not only in the physical field but also in resistance to disease and pollution. An interesting question now is: How large would such a group of animals need to be to make such adaptations to their genes in a rapidly changing environment?
Sources: PNAS, New York University via EurekAlert!
Image: Kristin Winchell
