Numbers count: caste-specific component Allee effects and their interactions.

A queen and worker of the Argentine ant Linepithema humile. The numbers of queens and of workers in a colony each have positive relationships with components of fitness. Photo and copyright: Alexander Wild. In Focus: Luque, G., Giraud, T. & Courchamp, F. (2013) Allee effects in ants. Journal of Animal Ecology,. 82, 956-965. Allee effects, positive relationships between fitness and the number or density of conspecifics, are surprisingly widespread and are of profound importance for understanding ecological dynamics. Lucque et al. (2013) provide the first explicit demonstration of Allee effects in a social insect. Using laboratory colonies of the Argentine ant, they show that there are component Allee effects of both workers and queens which interact with negative frequency-dependent effects. Such Allee effects are central to the ecology and evolution of social insects, the societies of which provide a rich, experimentally tractable resource for understanding the mechanisms and impact of Allee effects.