For more than a century, brightly banded and sometimes deadly coral snakes have been held up as textbook examples of a mimicry system shaped by evolution, in which a harmless species deters predators by imitating a harmful one.
More than 150 species of coral snake mimics have been identified, each bearing the distinctive red-and-black banding of its venomous counterpart. Even so, coral snake mimicry remains controversial among some biologists because of perceived conflicts between theory and observation.
Now, by combining genetic data and information from 300,000 snake specimens housed at natural history museums around the world, a University of Michigan-led research team says it has resolved part of the century-old conflict known as the coral snake mimicry problem.
U-M evolutionary biologist Alison Davis Rabosky and her colleagues showed that much of the apparent conflict between theory and observation disappeared when the global distribution of all snake species was taken into account.
In a paper published online May 5, 2016 in Nature Communications, they present the first definitive evidence that the spread of coral snakes throughout the Western Hemisphere over the last 40 million years drove the distribution of the mimics.
During that time, the distinctive coloration of the coral snake mimics evolved independently at least 19 times in the New World, according to the researchers. And in all instances, red-and-black-banded mimics arose only after coexisting with coral snakes, as predicted by mimicry theory.
“By using pioneering, global-scale tests only possible with the ‘big data’ from natural history museums, we show how coral snake mimicry can persist, despite breaking all the rules,” said Davis Rabosky, an assistant research scientist in the U-M Department of Ecology and Evolutionary Biology and an assistant curator of herpetology at the Museum of Zoology.
“We also identify profound gaps in mimicry theory and thereby provide new insights into the best targets for future research,” she said.
The other U-M authors of the Nature Communications paper are graduate students Pascal O. Title and Iris A. Holmes.