New colony formation in the "highly inbred" eusocial naked mole-rat: outbreeding is preferred

If the adaptive significance of sexual reproduction derives from genetic recombination, then sexual organisms that severely inbreed minimize the benefits of sexuality without fully escaping its costs. Local populations of the eusocial naked mole-rat are extremely genetically uniform, and colonies have the highest inbreeding coefficient known for wild mammals. Because nonbreeding workers cooperate to rear the queen's offspring, researchers have speculated that the inclusive fitness benefits of close relatedness outweigh the benefits of genetic recombination, thus leading to the adaptive avoidance of outbreeding. However, I show that in laboratory colonies in which each individual had an equal number of familiar siblings and unfamiliar distant kin (UDK) as potential mates, mating pairs were significantly more likely to consist of UDK. Some form of kin recognition must have been used in order for this pattern to result. Aggression was not mitigated by relatedness, however, as both fighting and cooperation occurred as frequently between siblings as between UDK. By studying the early stages of colony development I was able to investigate col relations between physical characteristics of workers and success in attaining breeding status. I also observed allonursing, hitherto unseen in this species, and suggest that it is less likely to occur later in colony development.