Social insects exhibit a sophisticated social structure in which queens reproduce and workers engage in tasks related to brood-rearing and colony defense. By investigating the evolution of genes associated with castes, sexes and developmental stages of the invasive fire ant Solenopsis invicta, the researchers explored how social insects produce such a diversity of form and function from genetically similar individuals.
"Social insects provided the perfect test subjects because they can develop into such dramatically different forms," said Goodisman.
Microarray analyses revealed that many fire ant genes were regulated differently depending on whether the fire ant was male or female, queen or worker, and pupal or adult. These differentially expressed genes exhibited elevated rates of evolution, as predicted. In addition, genes that were differentially expressed in multiple contexts -- castes, sexes or developmental stages -- tended to evolve more rapidly than genes that were differentially expressed in only a single context.
To examine when the genes with elevated rates of evolution began to evolve rapidly, the researchers compared the rate of evolution of genes associated with the production of castes in the fire ant with the same genes in a wasp that does not have a caste system. They found that the genes were rapidly evolving in the genomes of both species, even though only one produced a caste system. These results were also replicated for the honeybee Apis mellifera.
"This is one the most comprehensive studies of the evolution of genes involved in producing developmental differences," Goodisman noted.
This study helps explain the fundamental evolutionary processes that allow organisms to develop different adaptive forms. Future research will include determining what these fast-evolving genes do and ho
|Contact: Abby Robinson|
Georgia Institute of Technology Research News