This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Yale research scientist Saúl Domínguez-Guerrero didn't set out to catch "evolution in the act" when he traveled to the Caribbean with a team of Yale researchers a few years ago. At the time, the team from the lab of evolutionary biologist Martha Muñoz planned to do fieldwork on Caribbean anoles, colorful, tree-dwelling lizards native to warmer regions of the Americas.
The team was studying many species of these reptiles as part of a project to determine the role that behavior plays in shaping physiological evolution. Having studied these lizards in the past, they thought they knew what they'd find. But back in New Haven, their data told an unexpected story.
Their findings were published in the Proceedings of the National Academy of Sciences. "Saúl comes into my office one day and says, 'Martha, I'm noticing something weird in the temperature readings, and I think there might be something interesting going on here,'" recalled Muñoz, an associate professor of ecology and evolutionary biology in Yale's Faculty of Arts and Sciences. Specifically, Domínguez-Guerrero found that the ability of some lizards to withstand blistering temperatures had increased markedly over just a decade, a sign of physiological adaptation.
"I observed these shifts in heat tolerance," said Domínguez-Guerrero, who has been studying thermal adaptation in animals since his days as a doctoral student in Mexico. "But the surprising aspect was that the shifts were not distributed uniformly across all the lizard species." Access to longitudinal data threw a brighter spotlight on these discrepancies. Muñoz's team and other researchers had collected data from the same range of species on the same islands—Hispaniola, Jamaica and Puerto Rico—a decade earlier.
The change over time was indisputable. You're onto something,'" Muñoz recalled. "These different lizard species are not evolving in the same way at the same time." According to their findings, the data revealed that lizard species living in open or forest-edge environments, which could scurry to cooler spots when temperatures rose, showed little change in their ability to tolerate extreme heat; these animals were regulating that tolerance through a practice known as behavioral thermoregulation.
In contrast, they found that heat tolerance levels for species living deep within closed forest canopies—which have far fewer behavioral opportunities to escape the heat—had risen by an astonishing 2 degrees Celsius over just a decade. The results show that habitat can shape both the rate of a species' response to a warming environment and how that adaptation unfolds. Animals in a habitat that offers greater behavioral control over exposure to heat may have less need to evolve increased heat tolerance, while species that can't easily escape heat face stronger pressure to adapt physiologically.
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