GENETICS OF RESISTANCE OF SALIX SERICEA TO A DIVERSE COMMUNITY OF HERBIVORES

We measured resistance of Salix sericea, the silky willow, to a diverse assemblage of 12 herbivores. We investigated the potential for multispecies coevolution among these herbivores by measuring genetic correlations between pairs of herbivores interacting within the component community. After measuring herbivore attack on half-sib families of potted S. sericea during three years, we found significant narrow-sense heritabilities of resistance to Phyllonorycter salicifoliella and Phyllocnistis sp. in 1991. Thus, there is the potential for selection on resistance to these two herbivores. Despite the many significant phenotypic correlations between herbivore abundances within a year, most genetic correlations between herbivore abundances within a year were not significant. The genetic and phenotypic correlation structure varied from year to year in this three-year study. Thus, it appears that there is the potential for evolution of resistance to the two herbivores for which we found significant heritabilities, but multispecies coevolution seems unlikely.