Date of Award
Shannon M. Murphy
Competition can have far-reaching consequences for the fitness and distribution of many organisms. In herbivorous insects, competition mediated by a third organism is more common than direct competition and has a strong effect on insect communities; yet most research on indirect competition among herbivores focuses on dietary specialists, and those studies that do include generalists tend to rear them on agricultural crops. My project examines species interactions at three levels: intraspecific competition (within species), interspecific competition (between species), and ecosystem engineering effects at the community level. I studied competition and community interactions of two temporally-separated species of herbivorous insects, western tent caterpillars (Malacosoma californicum) and fall webworms (Hyphantria cunea) on their shared host plant, chokecherries (Prunus virginiana). Within species, I found that time-lagged intraspecific competition reduced larval fitness, that plants that had been fed upon by tent caterpillars the previous season were tougher than plants that had not been fed upon by tent caterpillars, and that there were fewer tent caterpillar egg masses on plants that had tent caterpillars earlier in the season than plants without tent caterpillars. Between species, I found that bottom-up fitness effects on tent caterpillars and both top-down and bottom-up fitness effects on fall webworms which demonstrates that competition can take place in temporally separated generalists through both bottom-up and top-down effects. At the community level, tent caterpillars altered the arthropod community associated with their host plant primarily by increasing predator density by creating structural diversity on their host plants that survives and continued to alter the community into the next year.
My results suggest that dietary generalist insects can have strong competitive and community effects outside of outbreak and agricultural conditions.
Barnes, Elizabeth Ellen, "Competition and Community Interactions of Two Generalist Herbivores" (2017). Electronic Theses and Dissertations. 1366.
Recieved from ProQuest
Elizabeth Ellen Barnes