PARENT SESSION
Symposium #21: Effects of inbreeding and loss of genetic diversity on interactions with natural enemies.

Organized by: CT Ivey, DE Carr, and MD Eubanks
Wednesday, August 7. 1:00 PM to 4:30 PM. Crystal Ballroom, TCC.

Ecological and evolutionary consequences of genetic variation for interactions with natural enemies.

Ivey, Christopher^*,1, ¹ University of Virginia, Boyce, VA

ABSTRACT- Although interactions with natural enemies are among the most widely studied phenomena in ecology, remarkably little is known about how genetic variation can shape the outcome of these interactions. We examined the effect of inbreeding and the concomitant loss of genetic diversity in Mimulus guttatus on its interaction with the xylem-feeding spittlebug, Philaneus spumarius. Spittlebugs reduced flower number and biomass of plants. On experimentally inbred plants, however, the negative impact of spittlebugs was exacerbated. Inbreeding in host plants also significantly affected the fitness (adult biomass and development time) of spittlebugs. These findings pointed to a genetic basis to these interactions that was altered by a loss of heterozygosity from inbreeding. To examine the extent to which these interactions might evolve in response to natural selection, we then explored the genetic architecture of tolerance and resistance to herbivory, using a 15-family full diallel cross among plants. Despite the negative effects of herbivory on plants, we found almost no additive genetic variation for tolerance to herbivory, indicating little ability for tolerance to respond to natural selection. Furthermore, despite our earlier observations of significant inbreeding depression for tolerance to herbivory, dominance variation was minimal, which suggests that deleterious recessive alleles vary among family lines. In contrast, we found evidence for significant additive genetic variation for resistance to herbivory. This suggests that tolerance and resistance to herbivory are not genetically correlated, and that they can respond independently to natural selection. In sum, we found that interactions with natural enemies can have a complex genetic basis, and that the loss of genetic diversity through inbreeding can have important and unforeseen ecological consequences for these interactions.

KEY WORDS: inbreeding, species interactions, herbivory, genetic variation