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What DO Fringe-Toed Lizards, Uma Thurman and The San Andreas Fault Have in Common?
By Susana Rinderle
What does a six-inch lizard with fringelike scales on their hind toes have to do with the star of the "Kill Bill" films? And what can these animals teach us about plate tectonics? Apparently, a lot!
Fringe-toed lizards, one of the more iconic species, have a story to tell not only about the desert's ecology but also its geological and hydrological history. As a graduate student in evolutionary biology at San Diego State University and a postdoctoral fellow at the Smithsonian Institute, Andrew Gottscho, PhD., studied fringe-toed lizards in the Colorado Desert for nearly ten years, funded in part by the Howie Wier Memorial Grant from Anza-Borrego Foundation.
Fringe-toed lizards are specialized for living in the wind-blown sand habitats of the Colorado Desert, so their evolution is deeply impacted by tectonic features like the San Andreas fault system, which runs throughout. Andy focused his research on the following questions: (1) How important were glacial cycles and plate tectonics in shaping the genetic patterns within this group? (2) How many species of fringe-toed lizards are there really, and why is this a tricky question? (3) What are the conservation implications of genetic research on lizards?
To answer these questions, Andy and his colleagues analyzed genomewide data collected using "restriction-associated DNA sequencing," which involves randomly sampling thousands of short sequences of DNA scattered across the genome. A combination of species discovery methods and species validation approaches were used to delimit species, infer phylogenetic relationships, and estimate the lizard's population sizes, migration rates, and speciation times.
The research was published in Molecular Phylogenetics and Evolution in January 2017 and Zootaxa in May 2020. Andy also presented at the "AnzaBorrego: In Focus" lecture series last March. They found that the four lineages within this complex (Uma inornata, Uma notata, Uma cowlesi, and U. sp.) are, in fact, distinct species. Because fringe-toed lizards only live in fine wind-blown sand, mountains created by tectonic plate activity are significant barriers to their migration over deep time. The best example is the way the Coachella Valley fringe-toed lizard (U. inornata) separated from the Colorado Desert fringe-toed lizard (U. notata) due to the activity of the San Jacinto fault zone.
In the second publication, they followed up and named the new species. "Ultimately, after ten years of research," says Andy, "We described a new species of fringe-toed lizard from Mohawk Dunes, Arizona. We named it Uma thurmanae in honor of the actress Uma Thurman." The name started as a lunchroom joke at the Smithsonian because of the pun: genus Uma and the actress's first name. But all four authors admire Uma Thurman's career as an actress and philanthropist, so the name stuck.
Andy currently resides in Northern California, where he works as a scientific writer for 10x Genomics in Pleasanton and teaches part-time a few weekends a year at Merritt College in Oakland. However, he continues to be fascinated by his discoveries in Anza-Borrego Desert State Park, which led him to his current quest to understand better and write about the San Andreas fault system.
"I hope to change how people think about the San Andreas fault," he says. "It's more than a giant crack in the ground that causes earthquakes. It has shaped the topography of the whole west coast of North America from Cape Mendocino to Cabo San Lucas and the evolution of species like the fringe-toed lizard. Anza-Borrego is one of the best places to learn more, and I hope to show how my studies in lizards open up bigger questions, still to be answered."
If you would like to reach Andy, please contact him at andrew.gottscho@gmail.com .
