Stanford researchers develop system for field testing mechanisms of evolution

December 20, 2001

STANFORD, Calif. - Evolutionary biology has always faced a major hurdle - how to test a process that takes place over thousands, if not millions, of years. Researchers at Stanford University may have come up with a solution.

Genetic mutations and the possible mechanisms underlying evolution have been studied in laboratory animals for decades, said David Kingsley, PhD, professor of developmental biology and assistant investigator for the Howard Hughes Medical Institute. The challenge has been to find a means of applying what scientists know to be true in the lab to systems in the natural world. In a paper published Dec. 20 in the journal Nature, Kingsley and his team propose that a small spiny fish called the three-spine stickleback, and the gene-linkage map of the fish's chromosomes that the team has developed, may be the tools evolutionary biologists have been needing.

The key, according to Kingsley, was to find two populations, that unlike laboratory bred mice and rats, would have traits that had evolved naturally and yet could still be cross-bred.

"What we needed were two species that had diverged fairly recently, had distinct morphological differences, were fast-growing and easy to keep in the laboratory," said Kingsley. It was also important to find two species, Kingsley said, that could produce viable offspring in the lab even if they would not naturally mate in the wild. The group's intent was to develop a map of the inheritance patterns showing the links between genes from one generation to another. According to Kingsley, it is a system used to study genetics in laboratory-bred mice, but he wanted to develop a system that could test inheritance patterns, mutations, and ultimately the mechanisms underlying evolution in natural populations.

"It's part of an age-old debate," Kingsley said. "Does evolution occur through infinitesimally small genetic changes involving a very large number of genes, or does it occur through changes of large effect associated with a smaller number of genes?" In the lab, according to Kingsley, much of the focus is on single gene mutations of large effect, but how does this apply to evolution as it occurs naturally? Kingsley and his team turned to the genetic architecture of two populations of sticklebacks for some answers.

"What made sticklebacks so appealing was that not only did they meet our criteria from a molecular and genetics standpoint, but their ecology and behavior has also been widely studied by many other researchers," Kingsley said.

To develop the gene-linkage map of the fish's genome, Kingsley's team first designed a marking system that would allow them to follow the inheritance patterns of various genes from one generation to the next. Using the markers, the team crossbred two populations - a near-shore invertebrate feeding species and an open-water plankton feeding species. They followed the patterns of inheritance through several generations, developing a genome-wide gene linkage map. Next, they used the map to analyze the genetic basis for a number of evolutionary changes that occurred in the two populations, such as the amount of body armor, the number of gill rakers and the length of the stickleback's spines.

Kingsley said they found a number of parallels between traditional laboratory genetics and the traits they examined in the stickleback populations. For example, many of the traits could be traced to major chromosome regions - indicating that evolution can occur through changes of large effect, not just as a series of small changes. Their findings also indicate that genetic control of body regions appears to be modular. The genes that control the length of the first dorsal spine, for instance, are located on different chromosome regions from the genes that control the length of the second dorsal spine. This is not surprising, said Kingsley, because it follows previous findings of the genetic control of mouse skeleton development. As anyone who plays with Legos can testify to, a modular body plan greatly increases the options for tweaking designs over time.

"The goal of this project was to develop a system that makes it possible to bring what we know in the laboratory about molecular genetics and begin applying it in the field to evolutionary theory and ecology," said Kingsley. The initial results, he said, suggest that these fish can now be used for detailed genetic studies of the mechanisms that control vertebrate evolution.

Other authors on the paper include first author Catherine Peichel, PhD, research associate with the Howard Hughes Medical Institute and Stanford Department of Developmental Biology, as well as Kirsten Nereng, PhD, Kenneth Ohgi, PhD, Bonnie Cole, and Pamela Colosimo, PhD, from the Stanford Department of Developmental Biology, Alex Buerkle, PhD, from the Department of Biology at the University of Wisconsin - Eau Claire, and Dolph Schluter, with the Zoology Department and Centre for Biodiversity at the University of British Columbia.
-end-
MEDIA AND BROADCAST CONTACT: Sheila Foster at (650) 723-3900 or 723-6911 (safoster@stanford.edu)

Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital. For more information, please visit the Web site of the medical center's Office of News and Public Affairs at http://mednews.stanford.edu.

Stanford University Medical Center

Related Evolution Articles from Brightsurf:

Seeing evolution happening before your eyes
Researchers from the European Molecular Biology Laboratory in Heidelberg established an automated pipeline to create mutations in genomic enhancers that let them watch evolution unfold before their eyes.

A timeline on the evolution of reptiles
A statistical analysis of that vast database is helping scientists better understand the evolution of these cold-blooded vertebrates by contradicting a widely held theory that major transitions in evolution always happened in big, quick (geologically speaking) bursts, triggered by major environmental shifts.

Looking at evolution's genealogy from home
Evolution leaves its traces in particular in genomes. A team headed by Dr.

How boundaries become bridges in evolution
The mechanisms that make organisms locally fit and those responsible for change are distinct and occur sequentially in evolution.

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.

Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.

A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.

Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?

Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.

Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.

Read More: Evolution News and Evolution Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.