Document: CON-3-48-36

Preference and performance of a generalist herbivore on Q. agrifolia and Q. engelmannii seedlings from a southern California oak woodland.

DUNNING, C.E.* ¹, T.D.PAINE ¹ and R.A.REDAK ^1,2

University of California, Riverside, CA 92521 USA ¹
Center for Conservation Biology, Riverside, CA 92521 USA ²

Abstract:
Once established as seedlings, oaks face potential herbivory by mammals and phytophagous insects. Knowledge of the impact that insects have on oak seedlings planted in restoration programs is important for land managers and those interested in understanding the regeneration of oak species. To determine potential damage of a common generalist insect herbivore on oak seedlings , we conducted performance and preference tests with a grasshopper and two species of oaks occurring in a southern California oak grassland. To quantify herbivore performance, we measured leaf area of 30 Quercus agrifolia and 30 Quercus engelmannii seedlings and caged them individually within acetate feeding arenas. Sixty fourth-instar Melanoplus sanguinipes were collected from Santa Rosa Plateau Ecological Reserve and placed in the individual feeding cages. We measured final dry weights of all frass and grasshoppers after a 20-day feeding period. To determine preference between the two species of seedlings, we placed 30 M. sanguinipes into paired feeding chambers and measured extent of leaf area feeding damage after 14 days. M. sanguinipes consumed significantly more leaf area and produced significantly more frass when feeding only on Q. agrifolia (P<0.001). Additionally, grasshoppers feeding on Q. agrifolia gained significantly more biomass (P<0.001), whereas those feeding on Q. engelmannii actually lost biomass. This research determined the preference and performance of M. sanguinipes when provided with only oak seedlings upon which to feed and indicates potential damage this common grasshopper can do in restoration studies with the threatened Engelmann oak.

Keywords: oak, restoration, seedling, insect, herbivory, preference, performance, Quercus engelmannii

This abstract is being presented at: 10:45 AM in session:
Oral Session #26: Invertebrate Herbivore - Plant Interactions.