Plant polyploidy and non-uniform effects on insect herbiwillow-feeding sawflies (Hymenoptera: Tenthredinidae

Genomic duplication through polyploidy has played a central role in generating the biodiversity of £ower-ing plants. Nonetheless, how polyploidy shapes species interactions or the ecological dynamics of communities remains largely unknown. Here we provide evidence from a 4 year study demonstrating that the evolution of polyploidy has reshaped the interactions between a widespread plant and three species of phytophagous moths. Our results show that polyploidy has produced non-uniform e¡ects, with polyploids less attacked by one insect species, but signi¢cantly more attacked by two other species. These results suggest that the evolution of plant polyploidy may not generally confer uniform resistance to multiple species of insect herbivores. In the absence of such a uniform release, the extreme evolutionary success of polyploid plants is probably due to factors other than escape from herbivory. Together, these results suggest that a primary consequence of plant polyploidy may be to shape the ecological structure of plant^ insect interactions, thereby providing opportunities for diversi¢cation in both plant and insect taxa