SPOILS OF WAR AND PEACE: ENEMY ADOPTION AND QUEEN-RIGHT COLONY FUSION FOLLOW COSTLY INTRASPECIFIC CONFLICT IN ACACIA ANTS

Intraspecific conflict over vital limited resources can lead to costly fights. How winners compensate for costs and minimize the threat of Pyrrhic victory is not well known. This study tracked the outcomes of experimentally induced field conflicts between highly territorial Acacia ant Crematogaster mimosae colonies using molecular genetics, and discovered that fatal fights significantly decrease within-colony worker relatedness. We find that reduced relatedness can be explained by colonies increasing worker number via 1) non-kin enemy adoption or 2) queen-right colony fusion. We hypothesize that incorporating non-kin enemies can speed recovery from conflict when resource defense is paramount. In the case of queen-right colony fusion, territorial defense benefits could outweigh fitness costs. We provide evidence that winners of colony fights have reduced worker forces to defend larger territories. Field assays indicate that post-fight colonies are more vulnerable to heavy browsing of host trees by mega-herbivores and takeover by competitors following conflict. We discuss the implications of our findings for ant colony cohesion and recognition systems.