Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers Find Genetic Evidence That Turtles Are More Closely Related To Birds Than Lizards And Snakes

25.05.2012
The evolutionary origin of turtles is one of the last unanswered questions in vertebrate evolution.

Paleontological and morphological studies place turtles as either evolving from the ancestor of all reptiles or as evolving from the ancestor of snakes, lizards, and tuataras. Conflictingly, genetic studies place turtles as evolving from the ancestor of crocodilians and birds.

Having recently looked at more than a thousand of the least-changed regions in the genomes of turtles and their closest relatives, a team of Boston University researchers has confirmed that turtles are most closely related to crocodilians and birds rather than to lizards, snakes, and tuataras.

The researchers published their findings in the Royal Society journal Biology Letters. By showing that turtles are closer relatives to crocodiles and birds (archosaurs) than lizards, snakes and tuatara (lepidosaurs), the study challenges previous anatomical and paleontological assessments. Nick Crawford, a post-graduate researcher in biology in BU’s Graduate School of Arts & Sciences and lead author of the study, achieved these findings by using computational analysis to examine regions of the different animals’ genomes.

“Turtles have been an enigmatic vertebrate group for a long time and morphological studies placed them as either most closely related to the ancestral reptiles, that diverged early in the reptile evolutionary tree, or as closer to lizards, snakes, and tuataras,” says Crawford.

The study is the first genomic-scale analysis addressing the phylogenetic position of turtles, using over 1000 loci from representatives of all major reptile lineages including tuatara (lizard-like reptiles found only in New Zealand). Earlier studies of morphological traits positioned turtles at the base of the reptile tree with lizards, snakes and tuatara (lepidosaurs), whereas molecular analyses typically allied turtles with crocodiles and birds (archosaurs).

The BU researchers challenged a recent analysis of shared microRNA families that suggested turtles are more closely related to lepidosaurs. They did this with data from many single-copy nuclear loci dispersed throughout the genome, using sequence capture, high-throughput sequencing and published genomes to obtain sequences from 1145 ultraconserved elements (UCEs) and their variable flanking DNA. The resulting phylogeny provides overwhelming support for the hypothesis that turtles evolved from a common ancestor of birds and crocodilians, rejecting the hypothesized relationship between turtles and lepidosaurs.

The researchers used UCEs because they are easily aligned portions of extremely divergent genomes, allowing many loci to be interrogated across evolutionary timescales, and because sequence variability within UCEs increases with distance from the core of the targeted UCE, suggesting that phylogenetically informative content in flanking regions can inform hypotheses spanning different evolutionary timescales. The combination of taxonomic sampling, the genome-wide scale of the sampling and the robust results obtained, regardless of analytical method, indicates that the turtle–archosaur relationship is unlikely to be caused by long-branch attraction or other analytical artefacts.

The BU study is the first to produce a well-resolved reptile tree that includes the tuatara and multiple loci, and also is the first to investigate the placement of turtles within reptiles using a genomic-scale analysis of single-copy DNA sequences and a complete sampling of the major relevant evolutionary lineages. Because UCEs are conserved across most vertebrate groups and found in groups including yeast and insects, this framework is generalizable beyond this study and relevant to resolving ancient phylogenetic enigmas throughout the tree of life. This approach to high throughput phylogenomics—based on thousands of loci—is likely to fundamentally change the way that systematists gather and analyse data.

About Boston University—Founded in 1839, Boston University is an internationally recognized private research university with more than 30,000 students participating in undergraduate, graduate, and professional programs. As Boston University’s largest academic division, the College and Graduate School of Arts & Sciences is the heart of the BU experience with a global reach that enhances the University’s reputation for teaching and research.

Nicholas Crawford | Newswise Science News
Further information:
http://www.bu.edu

More articles from Life Sciences:

nachricht Microscope measures muscle weakness
16.11.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg

nachricht Good preparation is half the digestion
16.11.2018 | Max-Planck-Institut für Stoffwechselforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Purdue cancer identity technology makes it easier to find a tumor's 'address'

16.11.2018 | Health and Medicine

Good preparation is half the digestion

16.11.2018 | Life Sciences

Microscope measures muscle weakness

16.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>