Sunday, September 30, 2007

Altruism in wasps tied to maternal behavior

ScienceDaily reports on an interesting study of wasps, where to researchers took a look at the genes of the different types of wasps, and saw if there was any connection to their genes.

Altruism Evolved From Maternal Behavior, Wasp Genetics Study Suggests

Researchers at the University of Illinois have used an innovative approach to reveal the molecular basis of altruistic behavior in wasps. The research team focused on the expression of behavior-related genes in Polistes metricus paper wasps, a species for which little genetic data was available when the study was begun.

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.

I don't get the use of 'Darwinian' unless it refers to some predictions made by Darwin. Even if it does, the reference to the prediction seems a bit weird, as it has long been known that evolution works on the species level, so it's not important if one particular individual reproduces, but rather that the species on the whole, reproduces in the most efficient way possible. For some species that apparently involves "a eusocial society" (an expression I've never heard before).

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.

So, queens have a different behavioral gene expression than foundresses, who are more similar to workers in their expression than queens and gynes (future queens in existing colonies). So, in other words, worker wasps (bees, etc.) are more maternal even though they are unable to sexually reproduce.

That's quite interesting.

It does not follow that all observed altruistic behavior have roots in maternal (or paternal) behaviour, but it would follow from what we generally know about evolution.

The study can be found here (behind a paywall)

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