The ants nest as extended phenotype of the queen

By Branden Holmes (Surroundx) on November 28, 2010

The Hymenoptera, or social insects (ants, bees and wasps), have a very unusual family structure. In many species there is only a single female, the queen, which produces all other members of the nest. She controls the production of sterile female workers and males; this special system is called haplodiploidy. The colony as a whole functions as one superorganism with a specific division of labour amongst the various castes, or types, of social insect within a given nest. As only the queen reproduces, and the rest of the colony are all sterile, it is the genetic ability of the queen to create a highly organized colony which is being selected. Any colony which breaks out into mutiny will not produce a new queen to fly off and found a new colony. Thus only those females which successfully propagate a new generation of queens, pass on their genes.

The way that I like to look at an ant colony (or bee colony, or wasp colony for that matter) is that all of the workers and soldiers etc. are all parts of the queens extended phenotype: they are all a manifestation of her genes. Thus, even though this is far more extreme than what Richard Dawkins would consider to be an extended phenotype, it is the correct way to look at the relationship between all of the different individuals which make up an ant colony. (paragraph). Each sterile female worker has exactly the same genes as the queen. What makes the queen different from a worker is her diet. A worker will turn into a queen with a specific dietary change. But why is this? Because a queen can't decide when she dies, thus she cannot give instructions for a new queen to be created when she is a bout to die. The alternative, the colony producing another queen at an arbitrary time would result in two queens and a lot of confusion. The communication would soon breakdown as the two queens, being immobile egg producing factories, would be separated from each other. An agreed quota would not be reached and an excess of eggs would likely follow, and the extinction of the nest. (paragraph). The hierarchy of an ant colony, or the division of labour, is the same process that we humans went through, permitted to happen in our case by the agricultural revolution. Thus because there are significant parallels, solving one would to some degree solve the other. We know a great deal more about our own shift from the hunter-gatherer lifestyle to the specialized job lifestyle. Admittedly however, although we have queens, reproduction is shared amongst many women. The social insects have gone one step further than us. What started us off on the course towards specialized jobs for everybody, was the permanence that growing our own food allowed. Instead of mobile shelters, we could afford to put the effort into permanent homes because a regular food source was guaranteed. Thus I believe that we need to find the myrmecological equivalent of the catalyst for agriculture (some species of ants, namely species in the genera Atta do grow their own fungus in species gardens within the nest. Other species of ants farm aphid ‘[dairy] cows’, massaging the aphids gently with their antennae, convincing the aphid to give up some of its honeydew, which the aphid creates when it feeds on plant sap). (paragraph). The most fundamental difference between our own society and that of ants is the fact that one or a few queens are responsible for all reproduction in the colony. Because this is so, the queens have become so specialized that evolution has turned them into egg-producing machines. The queens have however paid for this by giving up their mobility. They must be attended to, and cared for, by the workers. This is reminiscent of the story of the sperm and the egg, except the parallel is not quite valid because the queen can regulate reproduction rates. Thus queens became immobile not to compensate for the ever less investment by sperms as eggs did, but for some other reason. Perhaps queens did take up the reproductive slack, the result of most female ants being too busy with their job to worry about producing offspring. But this notion is negated by the fact that the whole reason for existence is to reproduce. The decline in reproductive rates would have occurred much too fast for some of the females to evolve adaptations to counter this. But of course fecundity selection would have expunged the genes of the slow-reproducing ants.

About Branden Holmes
I am an amateur evolutionist interested in the theoretical side of the subject.

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