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Like honey bee workers, wasp workers give up their reproductive capabilities and focus entirely on nurturing their larval siblings, a practice that seems to defy the Darwinian prediction that a successful organism strives, above all else, to reproduce itself. Such behaviors are indicative of a eusocial society, in which some individuals lose, or sacrifice, their reproductive functions and instead work to benefit the larger group.
Behavioral scientists have long noted the similarity between the maternal behaviors of some wasps and the nurturing and provisioning activities of workers. Until now, no study had uncovered a genetic link between the two. The researchers found that the pattern of behavior-related genes expressed in the brains of worker wasps was most similar to that seen in foundresses, the female wasps who alone build new colonies and devote much of their early lives to maternal tasks.
?These wasps start out as single moms,? said postdoctoral researcher Amy Toth. ?They don?t have any workers to help them, so they?re responsible for laying all the eggs and provisioning the developing larvae which then turn into workers.? The researchers selected this species because it appears to represent an evolutionary transition. Once a foundress has raised a first generation of workers, she turns over the task of nurturing the larvae to the workers and devotes herself entirely to her ?queenly? reproductive function.
At this point, the researchers discovered, behavioral gene expression in her brain changes, becoming distinct from that seen during her maternal period. Toth noted that the P. metricus wasps represent a kind of intermediate stage in the evolution of eusocial behavior. The honey bee colony, in which queens never perform maternal tasks, is considered a more developed form of eusociality.
?In Polistes metricus wasps you have behavior that?s more similar to what you might see in a maternal ancestor,? Toth said. ?That was really important for our study.? The study team included researchers from 454 Life Sciences, a Connecticut-based company that has pioneered a method for sequencing short segments of DNA.
There is a theory that altruism has the evolutionary function to promote your own genes. So, altruism normally works in the "family", where you share a lot of genes with your relatives. But I guess you share maybe 10% of the genes with your neighbor too.