Snakes Leading in Evolutionary Arms Race, says USU Researcher
Japanese chefs who dissect pufferfish for the sushi delicacy “fugu” walk a fine line between life and death. Flesh from the slimy, scale-less fish makes lips tingle and gives diners an intoxicating buzz. But if diners ingest tissue from the fish’s liver, they’ll die within hours, asphyxiated by a neurotoxin 500 times deadlier than cyanide.
The same toxin, tetrodotoxin or TTX, is found in the innocuous-looking newt, Taricha, that makes its home along America’s Pacific coast. Ordinarily, predators that swallow the newt crawl to a permanent halt – their nerves and muscles paralyzed. But not Thamnophis sirtalis, a garter snake found in certain geographic pockets that has evolved an amazing resistance to the toxin and feasts on the newts unharmed.
Utah State University alum Charles Hanifin, a postdoctoral fellow at Stanford University’s Hopkins Marine Station, USU biology professor Edmund Brodie, Jr. and Brodie’s son, Edmund Brodie III of the University of Virginia, reported their findings on this evolutionary ‘arms race’ this month in the online journal PLoS Biology.
The biologists made a surprising discovery in four research sites among the 28 habitats they’ve studied on America’s west coast – the snakes are winning.
Brodie, Jr., who’s studied anti-predator mechanisms in amphibians and reptiles since the mid-1960s, has long documented the balance between toxicity and resistance between the two species.
“Our expectation has been that toxicity and resistance should essentially match,” says Brodie. “That is, the snakes should develop enough resistance to eat the newts but still be somewhat affected by the toxin.”
But what Brodie and colleagues found in certain areas were garter snakes that have evolved what the scientists refer to as “super resistance.”
“This is an exciting finding that was not expected,” he says. “This is the first time we’ve had enough data to determine that, in some instances, the snakes have an edge.”
Are the team’s recent findings bad news for newts? No, says Brodie, newts aren’t in trouble from snake predation.
“What newts have in their favor is they produce a lot of eggs,” he says. “Plus, the snakes that have developed resistance are only found in certain areas.”
The snakes and newts make valuable study subjects, Brodie says, because the scientists can readily identify the factors that, over thousands of years, continue to fuel the battle of the species.
“What’s evolving is the level of TTX in the newts and one specific change in the snake’s nervous system,” he says. “We’re able to conduct a qualitative study in these species that isn’t possible in many studies of coevolution.”
The study, funded primarily by the National Science Foundation and support from the National Geographic Society, is exciting, Brodie says, because it’s the culmination of years of study and “sets the stage for continuing research.”
“Stay tuned,” he says. “We expect to report more findings in the near future.”
Related links:
“Phenotypic Mismatches Reveal Escape from Arms-Race Coevolution,” PLoS Biology
“USU Biologist Receives National Award for Excellence,” Utah State Today
Contact: Edmund “Butch” Brodie, Jr. [brodie@biology.usu.edu], 435-797-2489
Writers: Nadene Steinhoff; Mary-Ann Muffoletto [maryann.muffoletto@usu.edu], 435-797-3517
Writers: Nadene Steinhoff; Mary-Ann Muffoletto [maryann.muffoletto@usu.edu], 435-797-3517
A garter snake consumes a poisonous newt. Research conducted by USU biologist Edmund Brodie, Jr. and colleagues reveals new information about coevolution. Photo courtesy of Dr. Brodie.
USU biology professor Edmund Brodie, Jr. and his former doctoral student Charles Hanifin, now a postdoc fellow at Stanford, along with Brodie's son, Edmund Brodie III, University of Virginia, published their findings in this month’s PLoS Biology.
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