PARENT SESSION
Oral Session # 53: Herbivory IV: Communities, Populations, and Genetics.
Presiding: JA Rudgers
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 103.

Inbreeding alters tolerance and resistance to herbivory in natural settings.

Ivey, Christopher^*,1, Carr, David¹, Eubanks, Micky², ¹ University of Virginia, Boyce, VA² Auburn University, Auburn, AL

ABSTRACT- Inbreeding is common in natural plant populations and is one of the most fundamental influences on plant biology. A few recent studies have reported that inbreeding also can alter ecological interactions with other species. We performed two experiments to test the effects of inbreeding on tolerance and resistance to herbivory in four populations of Mimulus guttatus in Napa County, California. Self- and outcross-fertilized plants were transplanted into field sites and scored for herbivore damage (resistance) and fitness at the end of the growing season. In a second experiment, self- and outcross-fertilized plants were transplanted into field sites, and half the plants were exposed to herbivory from a single spittlebug (Philaenus spumarius) nymph. Inbreeding increased resistance to herbivory in one population but had no effect in the other three. Inbreeding reduced tolerance to spittlebug herbivory in two populations, increased tolerance in a third, and had no effect in the fourth population. The presence of herbivores significantly magnified inbreeding depression for plant biomass in two populations and reduced inbreeding depression for plant developmental rate in a third population. Variation among populations in inbreeding effects is common and may reflect differences in inbreeding history. We also observed significant variation among plant families for inbreeding effects on tolerance, indicating the opportunity for selection by herbivores to improve population-level tolerance. These results emphasize that the indirect effects of inbreeding on fitness through altered ecological interactions are important to consider, especially for the management of small and fragmented populations where inbreeding risk is higher.

Key words: inbreeding, herbivory, plant defense, Mimulus guttatus