Colony-mate recognition in the weaver ant Oecophylla smaragdina

Understanding recognition systems is at the heart of a range of evolutionary, biological and social processes, including the immune response, reproductive barriers, mate choice, kin selection and the evolution of parasitism. Among social insects, nestmate or colony-mate recognition may evolve as a proxy for kin recognition, as social insect colonies usually consist of a family group. I sought to advance our understanding of recognition systems by studying colony-mate recognition in the arboreal weaver ant, Oecophylla smaragdina. In particular, I explored the effects of spatial and temporal variation in recognition cues, and variability in the capacity of individual ants to recognise non-colonial conspecifics, on the effectiveness of recognition systems. I used a novel technique for studying colony odour: near-infrared reflectance spectroscopy (NIRS). I found that colonies of weaver ants had distinctive spectral profiles, but that there were also significant differences in the profiles of nests within colonies. Significantly, the spectral characteristics differentiating colonies from each other and nests from each other were different. The level of aggression between colonies was positively correlated with the spectral distance between colonies, especially when only those spectral characteristics that differentiated between colonies were used to calculate spectral distance. I also found that the spectral characteristics of colonies changed over time. However, the spectra of a colony and an isolated nest from that colony did not diverge significantly over time, suggesting that these spectral changes may reflect genetically programmed seasonal changes. I detected no increase in aggression over time between colonies and their corresponding isolated fragment; however, the level of trophallaxis did increase. Neither spatial nor temporal variation in colony odour appears to impair the effectiveness of colony-mate recognition in weaver ants. I also explored the effect of spatial relationships on the levels of aggression ...