Pathways to parasitic strategies in ants

Abstract

Evolutionary biologists find delight in tracing their study topics back to Charles Darwin, and ant researchers are no exception. The dulotic habit of many ant species was highlighted by Darwin as one of the most sophisticated adaptive outcomes of natural selection (1). Dulotic ants raid nests of other ant species for pupae, so that when workers eclose from the raided pupae they start working for their dulotic host nest. Thus, dulotic ants gain work force with little investment, whereas the captured workers are deprived of evolutionary fitness. The wonderful ways in which ant species exploit each other’s behaviors to get their brood reared do not stop here, however. Some species are temporary social parasites whose queens infiltrate nests of other species and kill the resident queen, so that the host workers start rearing the parasite’s young, and the colony gradually turns into a colony of the parasitic species. So-called inquilines, workerless social parasites, live permanently in colonies of their host species alongside the host queens, relying on the host workers for rearing their offspring (2). Social parasitism is found outside ants as well, in wasps, bees, and even in birds such as cuckoos and cowbirds, but the diversity of such strategies is the highest in ants. In PNAS, Borowiec et al. (3) use phylogenomics to reconstruct the evolutionary routes to parasitic strategies taken by Formica ants and their connections to dispersal and nest-founding strategies more generally. Formica is a Holarctic ant genus that comprises the mound-building wood ants and their relatives, dominant in temperate and boreal ecosystems from coniferous forests to peat bogs to prairie. All the main types of social parasitism are found within the genus. In addition to diversity in social parasitism, Formica are remarkably diverse in their social ecologies: Some species live inconspicuous and submissive lives in … [↵][1]1 Email: heikki.helantera{at}oulu.fi. [1]: #xref-corresp-1-1