On opposite sides of the globe over millions of years, the snakes of North America and Australia independently evolved similar body types that helped them move and capture prey more efficiently.

Snakes on both continents include stout-bodied, highly camouflaged ambush predators, such as rattlesnakes in North America and death adders in Australia. There are slender, fast-moving foragers on both continents, as well as small burrowing snakes.

This independent evolution of similar body forms in response to analogous ecological conditions is a striking example of a phenomenon called convergence. Yet despite similarities in outward appearance, a new University of Michigan study shows that look-alike snakes from the two continents differ dramatically in at least one major attribute: diet.

"Most biologists tend to assume that convergence in body form for a group of organisms implies that they must be ecologically similar," said U-M evolutionary biologist Daniel Rabosky. "But our study shows that there is almost no overlap in diet between many of the snakes that are morphologically very similar."

Rabosky is an assistant professor in the Department of Ecology and Evolutionary Biology and curator of herpetology at the U-M Museum of Zoology. He is co-author of a paper on the topic published online June 10 in the journal Proceedings of the Royal Society B. The first author is U-M doctoral student Michael Grundler.

Michigan News press release