Selection for uniformity: xenophobia and invasion success

One reason why ants fascinate us is the seemingly bipolar nature of their social interactions: harmonious cooperation within, and extreme aggression across, colonies. Recent work by Giraud and colleagues and by Tsutsui and colleagues explores a behavioral outlier in this dichotomy, the invasive Argentine ant Linepithema humile. Introduced L. humile often form unicolonial societies in which conflict between colonies is absent. Using theoretical, laboratory and field-based research, these researchers address an evolutionary paradox: the evolution of indiscriminate altruism.