Unicolonial ants: where do they come from, what are they and where are they going?

Unicolonial ant populations are the most extensive cooperative units known in nature, forming networks of interconnected nests extending sometimes hundreds of kilometers. Within such a supercolony, worker altruistic behavior might be maladaptive, because it seems to aid random members of the population instead of relatives. However, recent genetic and behavioral data show that, viewed on a sufficiently large scale, unicolonial ants do have colony boundaries that define very large kin groups. It seems likely that they are family groups that continue to express their kin-selected behavior as they grow to extreme sizes. However, at extreme sizes, kin selection theory predicts that these behaviors are maladapted and evolutionarily unstable, a prediction that is supported by their twiggy phylogenetic distribution.