Friday, September 28, 2007

Altruism in Social Insects

Why do some species, like honeybees, exhibit altruistic behaviour like giving up sex and even their own life for the colony? This week's Science podcast helps cast light on this question. You can listen to it here.

The Podcast addresses the findings in this paper, entitled "Wasp Gene Expression Supports an Evolutionary Link Between Maternal Behavior and Eusociality" by Amy L. Toth et. al.

Below are a few excerpts from the transcript of the podcast.

Interviewee – Amy Toth
We are interested in trying to understand the origins of social behavior in animals. And the reason that is so interesting is because it’s really been a long standing mystery that has intrigued many biologists -- even since Darwin -- because typically you think in evolution any animal’s goal in life is to survive and reproduce, so how do we explain something as extreme as, for example, a honeybee, that stings and loses its life to defend its colony. And so basically the question we are asking is where does this type of unselfish or altruistic behavior come from.

....Interviewer – Robert Frederick
Okay, so what was your hypothesis going into this experiment, then?

Interviewee – Amy Toth
We hypothesized that there would be a similar biological basis underlying maternal behavior and altruistic or worker behavior in a social insect. And so if those two behaviors were related in an evolutionary sense, then you might expect them to have very similar types of underlying biological basis.

....Interviewer – Robert Frederick
So, what kind of overlap was there then between the paper wasp and the honeybee?

Interviewee – Amy Toth
Yeah, that’s a good question. So, we can’t answer that definitively because we handpicked our genes. And so what we would really need to do is pick a random set from wasps and a random set from bees to get an unbiased estimate of what the overlap was. And so what we can say is based on the 32 genes that we did look at -- and we probably picked genes that are more interesting and potentially more likely to show differences -- we saw about 62% of those showed differences in the wasps that were associated with behavior. So, a very high percentage were showing interesting differences in gene activity in the brains of the wasps.

Interviewer – Robert Frederick
Did the expression of these genes backup what had been observed in the wasp as far as how it was different than the honeybee in terms of the rearing behavior of the wasps?

Interviewee – Amy Toth
So, a lot of them did, I would say follow up with an expectation we had. So, as I had mentioned before some of the genes that we chose were associated with foraging behavior in honeybees, and, in fact, a big part of being a worker or being a maternal foundress in these wasp colonies is foraging. And so we actually saw quite a few of the genes that were associated with foraging in honeybees. They also appeared to be turned on or turned off in specific ways in the brains of wasps that were foraging. And this foraging is an essential part of being maternal or being a worker.