Is this evidence of natural selection, with those lizards that just happened to have a lower cold tolerance surviving and others freezing to death, or was it an example of physiological adjustment-termed 'acclimation'- in which exposure to lower temperatures changes a lizard's physiology so that it is capable of withstanding lower temperatures?" "What we now need to find out is how this was accomplished. Danforth Distinguished University Professor and professor of biology in Arts & Sciences and director of the Living Earth Collaborative at Washington University. Who would have thought that tropical lizards from places like Puerto Rico and Central America could withstand temperatures near freezing?" said Jonathan Losos, the William H.
"The results of this study are surprising and unexpected. "And so in our paper we discuss other alternative processes which may also have led to this pattern." "The shifts to tolerate significantly lower temperatures that we observed were so large that we found it unclear whether natural selection was responsible," Stroud said. The results provide evidence that tropical, cold-blooded creatures-often characterized as unable to withstand rapid changes in climatic conditions-can sometimes endure conditions that exceed their established physiological limits. Only one of the species in the study is native to the area the rest have been introduced to Florida over the past century, researchers noted. On January 21, 2020, the National Weather Service in Miami tweeted: "Falling Iguanas Possible Tonight" Credit: National Weather Service / Miami "We realized after the 2020 cold event that these data were now extremely valuable-we had the opportunity to re-measure the same lizard populations to observe if their physiological limits had changed in other words, could these species now tolerate lower temperatures?" "Prior to this, and for a different study, we had measured the lowest temperatures that six lizard species in south Florida could tolerate," Stroud said. This cold snap provided a unique opportunity to understand how they are affected by extreme climate events.īut when the researchers collected the scaled survivors of that coldest night, they discovered that the lizard community responded in an unexpected way: all of them could tolerate cold temperatures down to about 42 degrees Fahrenheit, regardless of their species' previous ability to withstand cold. From previous research, Stroud and his colleagues had learned that different types of lizards in Miami can tolerate different low temperatures, ranging from about 46 to 52 degrees Fahrenheit, before they are stunned by cold. When temperatures go below a critical limit, sleeping lizards lose their grip and fall out of trees. "Today's the day to drop everything, go catch some lizards." While most people reached for an extra blanket or a pair of socks, Stroud-a postdoctoral research associate in Arts & Sciences at Washington University in St.
The previous night was south Florida's coldest in 10 years, at just under 40 degrees Fahrenheit. With its feet in the air, the iguana took up most of the sidewalk. A friend who was bicycling to work past the white sands and palm tree edges of Key Biscayne, an island town south of Miami, sent Stroud a picture of a 2-foot long lizard splayed out on its back. Biologist James Stroud's phone started buzzing early on Jan.
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