Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Biology

Supervisor

Dr. Jeremy McNeil

2nd Supervisor

Dr. Graham Thompson

Joint Supervisor

Abstract

Although social insects generally live within defined colony boundaries that are defended against intruders, under certain conditions populations may form expansive supercolonies with no evidence of overt aggression. Supercolony formation may be the result of an introduction event, where colonies lack aggression and possibly nestmate recognition, or may be related to the amount of resource abundance. In the case of the eastern subterranean termite (Reticulitermes flavipes) there are conflicting reports in the literature with regards to whether there is intraspecific aggression between colonies, some studies suggesting that aggressive behavior is displayed towards non-nestmates while others have concluded that it is a non-aggressive species. R. flavipes was first reported over 80 years ago in Toronto, where populations exhibit characteristics suggestive of supercolonies. However, more recently, genetically different populations have been found near Point Pelee where they form discrete colonies. The purpose of this thesis was to investigate the level of aggression and nestmate recognition within and between geographically different populations. If aggressive behavior exists then the level of intercolony aggression and mortality would be expected to increase with increasing geographic distance between colonies. Overall, no overt aggression was observed in any nestmate or non-nestmate pairings in 5-minute Petri dish trials (varying both caste and density). However, in two and seven-day resource design pairings the incidence of mortality was high in the non-nestmate assays when colonies from Toronto and Pelee Island were paired. Furthermore, in these assays nestmates readily intermixed while non-nestmates did not. These results indicate that R. flavipes recognizes kin from non-kin, regardless of their geographic origin or whether they form individual or supercolonies. Although they probably reduce aggressive interaction through the avoidance of non-kin, the high mortality observed in Toronto-Pelee pairings suggest that they express aggression under certain ecological conditions, possibly when foraging galleries intersect. It is also clear from this study that the design of the bioassay used can significantly affect the outcome observed, so care should be taken to test under conditions that are most reflective of field conditions.

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