Lizards that once scaled forest trees have genetically and physically adapted to survive urban life, according to a study published recently in the Proceedings of the National Academy of Sciences.
NYU researchers found that Puerto Rican crested anoles living in urban areas have grown toe pads with specialized scales that allow them to climb smooth surfaces and longer limbs that increase their running speed.
“We are watching evolution as it’s unfolding,” said Kristin Winchell, the study’s main author and a biology professor at NYU.
Winchell added, “The physical differences we see in the urban lizards appear to be mirrored at the genomic level.”
After catching and comparing 96 city-dwelling and forest-dwelling anoles, researchers found 33 genes directly associated with urban anoles.
Moreover, researchers found that the genes were matched across three separate cities: San Juan, Arecibo, and Mayagüez, which researchers say proves urbanization’s effect on the small brown lizard’s genetic makeup.
“There’s evidence that anoles have started to adapt to urbanization. You can see it in their genome,” said TCU biology professor Dean Williams to The Dallas Express. Williams was unaffiliated with the NYU research.
Williams, an expert on reptilian genetics, attributed the rapid genetic evolution of urban anoles to their quick reproductive cycle.
“It’s a numbers game,” explained Williams. “[Anoles’] population sizes tend to be very large which means there is more variability to select from.”
Anoles have a 7-year lifespan and reach reproductive age at eight months old. A single female anole can lay up to 168 eggs within her lifetime, contributing to a vast amount of genetic variation. Within 30 to 80 generations, anoles can develop population-wide mutations.
“The large population size allows anoles to develop certain traits that help them survive better in a changing environment,” said Williams.
Recently, Williams partnered with Texas Parks and Wildlife Department and the Fort Worth Zoo to reintroduce the Texas horned lizard, also called the horny toad.
Unlike the anoles, horny toads were unable to adapt to rapid environmental changes such as agricultural development and fire ants. The horny toads, which were once a dominant North Texas species, faced near extinction in the region.
As urbanization and agricultural development increase globally, Winchell believes her study will help scientists maintain biodiversity even in an urban environment.
“In many ways, cities provide us with natural laboratories for studying adaptive change,” added NYU’s Winchell. “Understanding how animals adapt to urban environments can help us focus our conservation efforts … [and] build urban environments in ways that maintain all species.”