Chris Martin has bred more than 3,000 hybrid fish in his time as a graduate student in evolution and ecology at UC Davis, a pursuit that has helped him create one of the most comprehensive snapshots of natural selection in the wild and demonstrated a key prediction in evolutionary biology.
"We can see a surprisingly complex snapshot of natural selection driving the evolution of new specialized species," said Martin, who with Professor Peter Wainwright published a paper on the topic in the Jan. 11, 2013, issue of the journal Science.
The "adaptive landscape" is very important for evolutionary biology, but rarely measured, Martin said. He's been fascinated with the concept since high school.
An adaptive landscape takes variable traits in an animal or plant, such as jaw size and shape, spreads them over a surface, and reveals peaks of success (what evolutionary scientists call fitness) where those traits become most effective, or adaptive.
It is a common and powerful idea that influences thinking about evolution. But while the concept is straightforward, it is much harder to map out such a landscape in the wild.
For example, about 50 species of pupfish are found across the Americas. The tiny fish, about an inch or so long, mostly eat algae on rocks and other detritus. Martin has been studying species found only in a few lakes on the island of San Salvador in the Bahamas, where some of the fish have evolved different-shaped jaws that allow them to feed on hard-shelled prey like snails or, in one case, to snatch scales off other fish.
In a paper published in 2011, Martin showed that these San Salvadoran fish are evolving at an explosively faster rate than other pupfish.
Martin brought some of the fish back to the lab at UC Davis and bred hybrids with fish with different types of jaws. He created about 3,000 hybrids in all, which were measured, photographed and tagged. Martin then took about 2,000 of the fish back to San Salvador.
"It was the craziest thing I've done," Martin said. "I was leaning on the stack of them in the middle of Miami airport."
Martin released the young fish into enclosures in the lakes of their grandparents. Three months later, he returned to check on the survivors and plotted them out on the adaptive landscape.
Most of the surviving fish were on an isolated peak adapted to a general style of feeding, with another peak representing fish adapted for eating hard-shelled prey. Competition between the fish had eliminated the fish whose jaws put them in the valleys between those peaks. The scale-eating fish did not survive.
The results explain why most pupfish species in America have pretty much the same diets, Martin said. The generalists are essentially stranded on their peak -- variants that get too far out fall into the valley and die out before they can make it to another peak.
"It's stabilizing selection," he said. An early burst of variation when fish entered a new environment with little competition could have allowed the shell-eaters and scale-eaters to evolve on San Salvador.
University of California - Davis: http://www.ucdavis.edu
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
The DNA in this ancient Siberian leg bone shows that the man had Neanderthal ancestors — yet more proof that humans and Neanderthals interbred. And he lived much farther north than expected.
The North Carolina coast may be the last place you'd think to find a sunken German submarine from World War II. But that's what Joe Hoyt — a nautical archeologist — found on a recent expedition to the ocean floor. Robert Siegel talks to him about the underwater battle site there.
Frustrated scientists argued Wednesday that making nasty viruses even worse in the lab provides crucial insight into preventing pandemics. Others say it just ups the risk a lab germ will start one.
The camel cousin evolved fluff instead of fat because it was able to linger in an evolutionary slow lane, suggest newly sequenced genomes
Archaeologists unearthed the missing head of one of the two sphinxes found guarding the entrance of an ancient tomb in Greece's northeast, as the diggers made their way into the monument's inner chambers, the culture ministry said on Tuesday.
In what the medical community is calling an incredible breakthrough, a Polish man who was left a quadriplegic after a stabbing, can walk again. The miraculous procedure involved doctors taking cells from his nose and implanting them into his spinal cord.
In a new book, San Francisco-based photographer Susan Middleton captures the curious gestures and expressions of marine invertebrates
Lab at the University of Texas at San Antonio gets Pentagon funding to see if brain waves can direct drone movement
After a severe brain injury, some people remain in a vegetative or minimally conscious state, unable to speak or move intentionally, and apparently unaware of the world around them. But in recent years, neuroscientists have found signs that some of these patients may still be conscious, at least to a degree. Now researchers have used a branch of mathematics called graph theory to search for neural signatures of consciousness.
Few parasitoids are more bizarre or disturbing than the wasps of the genus Glyptapanteles, whose females inject their eggs into living caterpillars. Once inside, the larvae mature, feeding on the caterpillar’s body fluids before gnawing through its skin en masse and emerging into the light of day. And despite the trauma, not only does the caterpillar survive---initially at least---but the larvae proceed to mind-control it, turning their host into a bodyguard that protects them as they spin their cocoons and finish maturing. Then, finally, the caterpillar starves to death, but only after the tiny wasps emerge from their cocoons and fly away.