PARENT SESSION
Oral Session #6: Insect Population and Community Ecology: Interactions, foodwebs.
Presiding: M. Hunter
Monday, August 5. 8:00 AM to 11:30 AM. Apache Meeting Room, TCC.
Interspecific competition and herbivorous insects: The importance of competition in the seed-feeding guild of wild sunflower.
PAULSEN, M.*,1, Pilson, Diana1, 1 University of Nebraska- Lincoln, Lincoln, NE
ABSTRACT- The role of interspecific competition in structuring herbivorous insect communities has been the subject of debate. Current opinion, which is based on recent reviews of experimental work, appears to favor competition as a widespread and frequent process. However, many studies have examined only a few species pairs within larger multi-species assemblages. In addition, the frequency of competitive interactions at the population level has not been evaluated by comparison with typical herbivore abundances. Thus, the importance of competition as a process structuring herbivorous insect communities remains unclear. We examined interspecific competition among 16 species pairs within the seed-feeding insect guild of wild sunflower, Helianthus annuus. In density manipulation experiments using typical high densities of herbivores we found that only 2 of 16 pairs of herbivores interacted competitively in the field. Moreover, an experiment examining the population-level impact of these negative effects suggests that herbivore populations are only infrequently (~ every 5-10 yr) regulated by competitive interactions. Our findings suggest that interspecific competition may have strong negative effects when it does occur, but that it is uncommon when all potential species pairs are evaluated, and is infrequent when natural densities are considered.
KEY WORDS: competition, insect, Helianthus