Australian, American snakes evolved to look alike

By Jacqueline Outred June 12, 2014
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Australian snakes evolved to have similar body forms as North American snakes, but they have quite different diets

AUSTRALIAN SNAKES HAVE evolved the same types of advanced body forms as their counterparts in North America, even though they’ve been on separate continents for millions of years, new research has shown.

“Australia has a death adder, a stout cryptically-coloured ambush predator that looks, for all practical purposes, like a typical [American] viper. But it’s not related to vipers and is much more closely related to other Australian elapid snakes,” says Dan Rabosky, evolutionary biologist at the University of Michigan and a co-author on the paper.

Studying the form and structure of a large number of preserved snake specimen, the researcher found that Australian snakes evolved and diversified to fill the same type of roles that different kinds of snakes occupy in North America demonstrating the evolutionary theory of convergence.

Australian snakes have a unique diet

Even though Australian snakes may have evolved with quite similar physical characteristics to North American snakes, they differ in one of the most important ecological attributes, say researchers: their diet.

“Most small snakes that live in sand or leaf litter in North America tend to eat arthropods like spiders and scorpions. But in Australia, those same snakes tend to be prefer lizards or other snakes; there is almost no overlap in diet between snakes that are otherwise very similar,” Dan says.

While North America’s snake population has evolved from many different groups, including rattlesnakes, gartersnakes and king snakes, Australia’s snake population has evolved from only one major group called the ‘elapids’ (which include cobras, coral snakes, mambas and kraits).

The American Chilomeniscus stramineus (l) and the Australian Simoselaps anomalus (r) look similar, but evolved on different continents over millions of years. (Credit: Kate Jackson/Dan Rabosky)

Snakes look the same but behave quite differently

The idea of convergence usually extends to the supposed function of animal features. “Most biologists tend to assume that convergence in the physical appearance for a group of organisms implies that they must be ecologically similar,” Dan says.

But this study shows that that assumption does not necessarily hold true. “Despite the extreme morphological similarity between Australian elapids and North American snakes, there are profound differences,” Dan says.

Dan hopes this new research, published by the Proceedings of the Royal Society B, will shed light on the spectacular evolutionary diversification of this ‘charismatic’ group of snakes.