Researchers evolve a complex genetic trait in the laboratory

Eureka Alert is reporting that Frederik Nijhout, of Duke University, and his colleagues have evolved a complex phenotypic trait, called a "polyphenism" (a complex trait that has several expressed forms) in the lab (see also the Science summary and links to the paper if you have access to it).

Taking black hornworm larvae, they exposed it to conditions of higher temperatures, in which a related species expressed a green phenotype. After ten generations, they have a variety that turns green. This is a process that Conrad Waddington called "genetic canalisation", in which mutations that make the selected trait easier to develop can become selected for. Typically this is done by heat shock of this kind.

Genomes under heat stress may be more susceptible to mutation, which may explain why this works, but Nijhout hypothesises this is due to selection for increased levels of the hormone that regulate development - a small increase in the hormone is enough to trigger a radical shift in phenotype (although fixing it in the population still requires mutations).