INTERSPECIFIC INTERACTIONS IN PHYTOPHAGOUS INSECTS - COMPETITION REEXAMINED AND RESURRECTED

This review reevaluates the importance of interspecific competition in the population biology of phytophagous insects and assesses factors that mediate competition. An examination of 193 pair-wise species interactions, representing all major feeding guilds; provided information on the occurrence, frequency, symmetry, consequences, and mechanisms of competition. Interspecific competition occurred in 76% of interactions, was often asymmetric, and was frequent in most guilds (sap feeders, wood and stem borers, seed and fruit feeders) except free-living mandibulate folivores. Phytophagous insects were more likely to compete if they were closely related, introduced, sessile, aggregative, fed on discrete resources, and fed on forbs or grasses. Interference competition was most frequent between mandibulate herbivores living in concealed niches. Host plants mediated competitive interactions more frequently than natural enemies, physical factors, and interspecific competition. Sufficient experimental evidence exists to reinstate interspecific competition as a viable hypothesis warranting serious consideration in future investigations of the structure of phytophagous insect communities.