Indirect interaction webs on tall goldenrod: Community consequences of herbivore-induced phenotypes and genetic variation of plants

Tall goldenrod, Solidago altissima, was introduced from North America 100 years ago, and it has become widely distributed all over Japan. We have been investigating plant-based indirect interaction webs on the tall goldenrod in Japan and the US. We found that arthropod communities on Japanese goldenrods are organized via plant- and ant-mediated indirect effects caused by the dominant aphid, Uroleucon nigrotuberculatum, which came from the US in the early 1990s. The aphid also generated bottom-up cascading effects on temporally separated communities. Our results highlight the importance of herbivore-induced plant phenotypes in determining the structure of indirect interaction webs. We review our ongoing research that focuses on the effect of plant genotypic variation on the formation of indirect interaction webs. Our findings of the genotypic effects on aphid population dynamics and herbivore community composition provide a more complete understanding of the community consequences of plant genotypic diversity, as well as herbivore-induced plant phenotypes.