Lazy ants "social cancer" of colony

Lazy "cheater ants" have been observed to take advantage of the hard working members of their colony for their own evolutionary advantage, according to research published today in the journal Proceedings of the Royal Society B: Biological Sciences.

Scientists at the University of Tokyo found that larger ants in the colony laid more eggs, but hardly took part in any of the co-operative activities, thus resulting in a lower fitness of the colony as a whole. These larger ants have been identified as a distinct genotype that seems to represent a lineage that has specialized in cheating described as a "social cancer" of the colony.

An important first step in the field study was to find a system containing both co-operators and cheaters living together under natural conditions. In colonies of this particular ant, females reproduce asexually and there are very few males in the population as a result. The usual queen caste is absent and the females share reproductive and work duties over the course of their life.

Evidence of such cheating is rare in the animal kingdom, but co-operation within a species has always been vulnerable to strategies that exploit the benefits of co-operation without paying the fair cost. This discovery is an important step towards the major goal of evolutionary biologists to explain where co-operation originated and why it continues to thrive, despite the obvious opportunities for cheating.