Their experiments, they said, offer important insight into how complex traits involving many genes can abruptly "blossom" in an organism's evolution.
The researchers -- Professor of Biology Frederik Nijhout and graduate student Yuichiro Suzuki -- published their findings in the Feb. 3, 2006, Science. Their work was funded by the National Science Foundation.
The complex traits, or "polyphenisms," they studied are instances in which animals with the same genetic makeup can produce quite different traits, or phenotypes, in different environments. For example, genetically identical ants can develop into queens, soldiers, or workers, according to their early hormonal environment. Or, the same butterfly can assume very different coloration in winter or summer. A kind of polyphenism is also likely at work in mammals -- for example in the seasonal development of antlers or changes in plumage or coat colors, said Nijhout and Suzuki.
While biologists have understood the basic machinery underlying polyphenisms, the mystery remained how such complex traits, which involve mutations in multiple genes, could evolve and persist.
"It's long been known that polyphenisms are controlled by hormones, with the brain sensing environmental signals and altering the pattern of hormonal secretions," said Nijhout. "In turn, these hormonal patterns turn sets of genes on or off to produce different traits. However, we understood only the developmental mechanism, and how it is possible with a single genome in an animal to produce two very different phenotypes," he said.