Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Researchers find a pattern in evolution of lizard groups


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:

More articles from Life Sciences:

nachricht Biologists unravel another mystery of what makes DNA go 'loopy'
16.03.2018 | Emory Health Sciences

nachricht Scientists map the portal to the cell's nucleus
16.03.2018 | Rockefeller University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

Im Focus: Radar for navigation support from autonomous flying drones

At the ILA Berlin, hall 4, booth 202, Fraunhofer FHR will present two radar sensors for navigation support of drones. The sensors are valuable components in the implementation of autonomous flying drones: they function as obstacle detectors to prevent collisions. Radar sensors also operate reliably in restricted visibility, e.g. in foggy or dusty conditions. Due to their ability to measure distances with high precision, the radar sensors can also be used as altimeters when other sources of information such as barometers or GPS are not available or cannot operate optimally.

Drones play an increasingly important role in the area of logistics and services. Well-known logistic companies place great hope in these compact, aerial...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

International Virtual Reality Conference “IEEE VR 2018” comes to Reutlingen, Germany

08.03.2018 | Event News

Latest News

Wandering greenhouse gas

16.03.2018 | Earth Sciences

'Frequency combs' ID chemicals within the mid-infrared spectral region

16.03.2018 | Physics and Astronomy

Biologists unravel another mystery of what makes DNA go 'loopy'

16.03.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>