What is a lizard? Emerging insights from studies of Heloderma
Beck, Daniel D.
Department of Biology
Central Washington University
Ellensburg, Washington USA
Gienger, Chris M.
Center of Excellence for Field Biology
Austin Peay State University,
Clarksville, Tennessee USA
Davis, Jon
Rockwell Real Estate
Medford, Oregon USA
DeNardo, Dale F.
School of Life Sciences
Arizona State University
Tempe, Arizona USA
Emblidge, Patrick
Northwest Bat Hub
Oregon State University – Cascades
Bend, Oregon USA
Goode, Matt
University of Arizona
Tucson, Arizona USA
Holcomb, Kerry
U.S. Fish & Wildlife Service - Southern Nevada Office
Las Vegas, Nevada USA
Jones, Jason
Western EcoSystems Technology, Inc. (WEST)
Cheyenne, Wyoming USA
Nowak, Erika
Colorado Plateau Research Station
Northern Arizona University
Flagstaff, Arizona USA
Arguably, our paradigm of “lizard biology” has historically been biased toward more commonly studied taxa, dominated by small, heliothermic species that are largely active on a daily basis. In this talk I’ll explore how knowledge of helodermatid lizard (Monstersaur) biology can inform other realms of herpetology, medicine, and conservation in ways that greatly enrich our answer to “What is a lizard?” Heloderma first appeared in seasonal tropical environments over 23 mya, and later colonized the Sonoran, Mojave, and Chihuahuan deserts of North America. Extant Monstersaurs span over 2000 miles and 22 of latitude from the Mojave Desert in Utah to the tropical dry forests of eastern Guatemala. The substantial molecular diversity of beaded lizards and their current geographic distribution align with the deep evolutionary history of neotropical dry forests of Mexico and Central America. I’ll present a preliminary summary of a large data set of body temperatures, assembled by Chris Gienger, a result of a collaboration over decades among many Heloderma researchers. Our data from populations along a 1500-mile latitudinal gradient, from the SW US to coastal Jalisco, show considerable variability in resting body temperatures (from 18 o C in Utah, to 25 o C in Jalisco). Yet preferred activity temperatures are fairly consistent throughout this latitudinal gradient, hovering around a mean of 30 o C for all populations. Use of GLP-1 agonists (developed directly from the exendin-4 peptide discovered in Gila Monster venom) have recently skyrocketed, powered by their promise as weight loss drugs. In 2023, the journal Science named these mega blockbusters the breakthrough of the year, the GLP-1 agonist market topped $35 billion, and Monstersaurs remain posterchildren for the value of biodiversity. So, what is a lizard? The answer is complex, awe inspiring, and beautiful. But, like the bumpy lizards of the Helodermatidae, can’t really be boxed into a simple definition.