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.
Photo by Daniel Rabosky.
The southern shovel-nosed snake is a small, desert-dwelling species of Australian elapid snake that feeds almost exclusively on lizard eggs.
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 to be published online June 10 in the journal Proceedings of the Royal Society B. The first author is U-M doctoral student Michael Grundler.
While North America is home to at least seven distinct groups of "advanced" snakes, only one major group—the elapids—colonized Australia roughly 12 million years ago. Elapids, which have hollow, fixed fangs through which they inject venom, are found worldwide and include king cobras, coral snakes, mambas and kraits.
Over millions of years, evolution allowed Australia's elapids to diversify and specialize through a process called adaptive radiation. They settled into varied habitats and split into roughly 100 species that include snakes with some of the most toxic venom known: taipans, brown snakes, death adders and tiger snakes.
Over time, the Australian snakes took on most of the body forms found in North American snakes.
Grundler and Rabosky compared those body forms by analyzing preserved specimens in the collections of the University of Michigan Museum of Zoology, the Field Museum of Natural History and the Western Australian Museum. They made measurements of head and body dimensions from 786 specimens representing 248 species.
"We found that the morphologies of Australia elapid snakes have evolved into the same types of body forms seen across a much more diverse set of snakes from North America," Grundler said. "For example, Australia has the death adder, a stout-bodied ambush predator that looks, for all practical purposes, like a typical viper.
"Vipers are a family of fanged, venomous snakes that includes pit vipers such as rattlesnakes, copperheads and bushmasters. But the death adder is not a viper and is in fact much more closely related to other Australian elapid snakes, most of which look nothing like vipers."
Grundler and Rabosky surveyed the published literature for data on the feeding habits of snakes on both continents. The feeding habits were placed in eight prey categories: invertebrates such as insects, earthworms, mollusks and crustaceans; fish; amphibians; lizards and snakes; lizard and snake eggs; birds; bird eggs; and mammals.
In many cases, Australian and North American snakes that are similar in appearance differ greatly in their diets, the U-M researchers found.
For example, most small snakes that live in sand or leaf litter in North America eat invertebrates such as spiders, scorpions, slugs and centipedes. But in Australia, those snakes tend to be specialists on lizards and other snakes.
The physical similarities between North American and Australian snakes are thought to reflect evolutionary advantages that those body forms provide for locomotion, foraging, or habitat use, according to the authors.
The research was funded by the National Science Foundation.
Daniel Rabosky: http://bit.ly/1xymDMK
Jim Erickson | newswise
Getting a grip on slippery cell membranes
28.06.2016 | Worcester Polytechnic Institute
Unexpected flexibility found in odorant molecules
27.06.2016 | Max-Planck-Institut für Struktur und Dynamik der Materie
R2D2, a joint project to analyze and development high-TRL processes and technologies for manufacture of flexible organic light-emitting diodes (OLEDs) funded by the German Federal Ministry of Education and Research (BMBF) has been successfully completed.
In contrast to point light sources like LEDs made of inorganic semiconductor crystals, organic light-emitting diodes (OLEDs) are light-emitting surfaces. Their...
High resolution rotational spectroscopy reveals an unprecedented number of conformations of an odorant molecule – a new world record!
In a recent publication in the journal Physical Chemistry Chemical Physics, researchers from the Max Planck Institute for the Structure and Dynamics of Matter...
Strands of cow cartilage substitute for ink in a 3D bioprinting process that may one day create cartilage patches for worn out joints, according to a team of engineers. "Our goal is to create tissue that can be used to replace large amounts of worn out tissue or design patches," said Ibrahim T. Ozbolat, associate professor of engineering science and mechanics. "Those who have osteoarthritis in their joints suffer a lot. We need a new alternative treatment for this."
Cartilage is a good tissue to target for scale-up bioprinting because it is made up of only one cell type and has no blood vessels within the tissue. It is...
Physicists in Innsbruck have realized the first quantum simulation of lattice gauge theories, building a bridge between high-energy theory and atomic physics. In the journal Nature, Rainer Blatt‘s and Peter Zoller’s research teams describe how they simulated the creation of elementary particle pairs out of the vacuum by using a quantum computer.
Elementary particles are the fundamental buildings blocks of matter, and their properties are described by the Standard Model of particle physics. The...
A year and a half on the outer wall of the International Space Station ISS in altitude of 400 kilometers is a real challenge. Whether a primordial bacterium...
09.06.2016 | Event News
24.05.2016 | Event News
20.05.2016 | Event News
28.06.2016 | Physics and Astronomy
28.06.2016 | Earth Sciences
28.06.2016 | Earth Sciences