In this week's Science, researchers report that polyphenisms - distinct phenotypes emerging from identical genomes - can evolve through genetic stabilization of a stress-induced phenotype. The authors suggest that complex traits, such as color change, may evolve suddenly when a mutation in a developmental hormone reveals previously hidden genetic diversity.The study makes an important contribution to understanding how polyphenic systems could evolve, according to David Pfennig of the University of North Carolina at Chapel Hill, who was not involved in the study. "We don't know a lot about the origins of these kinds of polyphenisms," Pfennig said. As part of the study, Yuichiro Suzuki and H. Frederik Nijhout of Duke University in North Carolina artificially selected for coloration change in response to heat stress in tobacco hornworm larvae. Ten generations of selection resulted in caterpillars polyphenic for larval color, with corresponding changes in levels of a developmental hormone. In...

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