Defending the nest: variation in the alarm aggression response and nest

摘要

A number of studies have found that ant colonies vary in many colony-level phenotypes, including the level of aggression towards non-nestmates. The extent of a colony's aggression and defense of the nest in response to attacks by predators is likely to affect its survival and reproduction, but the degree to which colonies vary in their defensive response is poorly known. We documented considerable variation in damage to the external nest mound of Pogonomyrmex occidentalis (Cresson) at our long-term study site in 2012. Heavily damaged colonies formed several spatial clusters, consistent with predation within a home range. We tested two competing hypotheses for the variation in nest damage: (1) colonies vary in their level of aggression, those with stronger defensive responses are better protected, and suffer less damage, versus (2) colonies have similar levels of aggression, but those that suffer predator-induced damage subsequently display a stronger defense response. We measured the alarm/aggression response in colonies exposed to a standardized stimulus and determined whether the level of aggression was correlated to the level of damage. Colonies with strong defensive responses were significantly less likely to exhibit damage than those with weak responses, suggesting that aggression level is a colony phenotype