All of us adapt to life in cities, and animals are no exception.
A new study shows that lizards living in urban areas have developed different genetic markers compared to those living in rural and forested areas. These genetic variations lead to physical differences, including larger toe pads and longer limbs—traits that are advantageous in an urban environment.
In fact, many animal species are trying to survive in urban environments.
Urbanization has significantly altered landscapes around the world, changing how animals interact with nature, creating “heat islands” with higher temperatures, and affecting biodiversity. While we view cities as human habitats, many other creatures are living in urban areas alongside us. In fact, many species among them are finding ways to survive in urban settings, adapting to the new habitats created by humans.
“Creatures living in urban environments face various pressures to survive, and they are forced to adapt to utilize new resources and manage new stressors related to infrastructure and human activities,” said Kristin Winchell, a biology professor at NYU and the lead author of the study, to ZME Science.
Winchell and her team conducted research on the Anolis cristatellus lizard, a species found in both urban and forested areas of Puerto Rico. In previous studies, they discovered that urban lizards had evolved certain traits to thrive in the city. They possess longer toes to grip smooth surfaces like walls and longer limbs to sprint across open areas.
In their new study, the researchers focused on a group of Anolis cristatellus lizards from three regions of Puerto Rico—San Juan, Arecibo, and Mayagüez. They measured the lizards’ morphology to quantify limb length and foot size, while also taking tail samples to extract DNA—subsequently sequencing part of the coding genes.
The results confirmed that the lizard populations in the three areas of Puerto Rico are genetically distinct from one another, suggesting that any similarities found among the lizard species in the three cities could be attributed to urbanization.
“Our study shows that adaptation in response to urbanization can occur in predictable ways. This means that, at least in this species, lizards have the genetic machinery to produce similar morphological adaptations whenever a population invades a city,” Winchell told ZME Science.
She added that these results open up many potential new research avenues, including areas that may help us understand how other organisms besides lizards are affected by the stresses of urban environments. Understanding how genetic changes impact the health, survival, and reproduction of organisms could be significant for their survival as urbanization increases.
About 55% of the world’s population currently lives in urban areas—a figure expected to rise to 68% by 2050, according to the United Nations. Urbanization, the gradual movement of people from rural to urban areas, combined with population growth, could add another 2.5 billion people to urban regions, with 90% of this growth occurring in Asia and Africa.
The size and color of each Anolis lizard species vary depending on their habitat, climate, and diet. Depending on where they live and how they hunt, they can exhibit physical adaptations such as larger hind legs for jumping large distances to catch prey or squat legs if they dwell in higher trees and creep slowly onto prey to avoid detection by predators while hunting.
They come in various colors, although the most common are a range of greens and browns, with yellow and sometimes blue variations.
Anolis lizards are primarily solitary creatures. They may live near one another but are often not found in groups. Males actively defend their territory during their sexual maturity; otherwise, they tend to be docile and tolerate human presence to varying degrees. Different adaptive behaviors occur depending on the environment they inhabit.
