Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers find a pattern in evolution of lizard groups

15.08.2003


Evolutionary biologists have developed a wide range of techniques to reconstruct the evolutionary history of particular groups of plants and animals. These techniques reveal much about the diverse patterns of evolution of life on earth, but few generalities have emerged, leading many scientists, such as the late Stephen Jay Gould, to conclude that each group of living things evolves in its own idiosyncratic manner. But now biologists at Washington University in St. Louis have proposed a general pattern among groups in the timing of evolutionary diversification.



Using novel statistical and analytical techniques, a group headed by Jonathan Losos, Ph.D. and Allan Larson, Ph.D., both Washington University professors of biology in Arts & Sciences, examined two important dimensions in the evolutionary diversification of four groups of lizards: the ages of branching points on the evolutionary trees of the lizard groups and variation among branches in morphological (body) traits, such as limb length and head size.

The researchers found that the four lizard groups differed in both respects. For example, in Australian agamid lizards, a disproportionate number of branching events occur deep (early) in the evolutionary tree, whereas, at the other extreme, among the South American Liolaemus lizards, the branching points are evenly distributed throughout the tree.


Similarly, the distribution of morphological variation differed in the four groups. In the agamids, closely related species tend to be morphologically similar and distantly related species morphologically different, whereas this relationship is much weaker for Liolaemus . In both cases, the other two lizard groups were intermediate.

What was most surprising to the researchers was that, despite the many differences among the four lizard groups, a strong overall relationship was found between the two aspects of evolutionary diversification. "This correlation was a big surprise," said Losos. "The general worldview is that the history of each lineage is unique and due to varying circumstances so that no general pattern exists. Our findings tend to dispute that."

The results were published in the August 15 issue of Science magazine. The research was supported by the National Science Foundation.

To reach their conclusions, the researchers produced a detailed genetic phylogeny (think of a branching family tree) for all species and physical data for the different species body types. Co-author James A Schulte, Ph.D., a former member of the Losos and Larson laboratories, now a post-doctoral researcher at the Smithsonian Museum of Natural History, gathered much of the phylogenetic and morphological data. Washington university graduate student Luke Harmon, the lead author on the paper, created a statistical program that uses phylogenies derived from genetic information (DNA sequences) from each species to estimate the patterns of branching and morphological change in each group.

"We can use the shape of these phylogenies, or evolutionary trees, to make conclusions about evolution," said Harmon. "For example, we can compare the lengths of branches on these family trees to determine the rate that new species were formed. Deeper branches on trees connecting species indicate older branching, while shorter ones indicate more recent speciation. People have been studying these patterns with fossil evidence for some time, but there is not much of a fossil record for lizards and many other terrestrial groups. I think the results will help biologists understand adaptive radiation better."

"We tentatively explain our main finding using ecological and biogeographic theory," said Larson. "Ecological theory suggests that ecologically similar species are unable to coexist through long periods of time in the same geographic area. If lineages with different ecological adaptations arose early in the history of a group, their descendants could coexist geographically through long periods of evolutionary time by maintaining those differences. If a group does not establish ecologically disparate lineages early in its history, lineages produced at the tips of the tree are more likely to explore a wide diversity of ecological roles."

Lizards have been on the earth for more than 200 million years. There are as many lizard species as there are mammal species, and they make excellent models to study for evolution, said Losos, who has been studying Anolis and other lizards for more than a decade. He and his collaborators plan to analyze more lizard groups to see if the general patterns revealed in this report hold.

Tony Fitzpatrick | EurekAlert!
Further information:
http://www.wustl.edu/

More articles from Life Sciences:

nachricht Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY

nachricht NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>