Population structure and predation in the harvester termite, Trinervitermes trinervoides (Sjöstedt).cwwpirk@zoology.up.ac.za

Abstract

Little information is available on the termite species in southern Africa, especially Trinervitermes trinervoides (Sjöstedt). This is an endemic, non-detrimental harvester termite that performs vital ecosystem functions in the semi-arid grassland ecosystem of southern Africa. T. trinervoides is the only termite species that does not compete with grazers for foraging material since they harvest litter grass. T. trinervoides are highly eusocial, mound-building, nasute termites. The ability to construct mounds has facilitated colonies in obtaining a population of thousands of individuals. Nevertheless it is unclear if T. trinervoides is monodomous (single mound) or polydomous (several mounds). The large population sizes in terms of individuals per mound and mound density of T. trinervoides have allowed for predator specialisation. In southern Africa the most destructive predator of T. trinervoides is the aardvark, Orycteropus afer (Pallas). In order to determine the impact of predation from the aardvark, the social structure of T. trinervoides first has to be understood. Using aggression as a proxy for nestmate recognition I found that each T. trinervoides colony occupies a single mound. The aggression structure was uniform across the population and most likely driven by resource competition. Aardvark predation risk was highest in the wet season, but predation severity was also uniform across the population. Predation from the aardvark may be driving T. trinervoides social structure towards monodomy in this area. Polydomy may decrease colony survival as resources are spread throughout a wide area. Furthermore this study reveals that large scale studies are important in ecological studies as small scale studies over emphasise variance in data that is reduced on a large scale.