EVIDENCE OF COMPETITION IN A HERBIVOROUS, GALL-INHABITING MOTH (LEPIDOPTERA) COMMUNITY

The larvae of a number of Lepidoptera species inhabit galls induced by the rust fungus Ravenelia macowaniana on Acacia karroo in South Afric a, and the community appears to fulfill the conditions required for in terspecific competition. Therefore, the aim of this study was to deter mine if the predominantly polyphagous moth community utilizing this ep hemeral, patchily distributed, yet high quality, resource, showed evid ence of exploitative intraspecific and interspecific competition. The galls were found to be extensively utilized with over 93% of galls occ upied and between 50-80% of gall tissue consumed. Fewer than 0.6% of t he larvae were parasitized. Significant, positive intra- and interspec ific aggregation occurred in the galls and the mean number of species per gall was consistently greater than one. A threshold density of 13 individuals, representing a total moth biomass of 12.74 mg, was found above which body mass compensation occurred. Resources are therefore l imited in the community. The species were positively associated as a r esult of a common habitat affinity. Species abundances also covaried p ositively in a common response to resource conditions. Resource limita tion and 'non-specific' exploitative competition was thus found in the Lepidoptera community.