Variation in plant-mediated intra-And interspecific interactions among insect herbivores: Effects of host genotype

Abstract

Many studies show that indirect interactions between insect herbivores via shared host plant are common and often mediated by plant-induce responses to damage. However, we lack some types o data that will be needed to model how plant-mediate interactions on individual plants contribute to th population dynamics of interacting herbivores. Specifically, there are few simultaneous characterization of both the intra-An interspecific effects that are mediated by the host plant, as well as host plant constitutiv resistance. Additionally, as herbivores are likely to move among plants that differ in quality, we mus consider how this set of intra-An interspecific effects differs among plant genotypes-that is, how plant-mediate effects genetically vary or covary. We examined how the set of intra-An interspecific indirec effects involving the insect folivores Leptinotarsa juncta and Manduca sexta varies across different genotype of a shared host plant, Solanum carolinense. We damaged 12 plant genotypes using both herbivore species then measured effects on the growth of both con-An heterospecifics, as well as constitutive resistance t each herbivore. We then tested for genetic variation and covariation in plant-mediate effects and constitutiv resistance among plant genotypes. We found that on average, there were significant negativ intraspecific plant-mediate effects on the growth rate of both herbivores, as well as asymmetric negativ interspecific effects of M. sexta on L. juncta. Both intra-An interspecific effects varied across plant genotypes For example, the interspecific effect of M. sexta on L. juncta ranged from significantly negative t significantly positive. Additionally, there were strong correlations among the individual effects mediate by S. carolinense, particularly between constitutive resistance and both intra-An interspecific effects. W find that these genetic correlations might limit the types and strength of interactions that take place acros multiple genotypes of the same plant species. Our results suggest that future models of plant-mediate interactions between herbivores should account for patterns of genetic variation and covariation whe scaling from individual interactions to population-leve processes. Copyright: