Distinct defense strategies allow different grassland species to cope with root herbivore attack

Root-feeding insect herbivores are of substantial evolutionary, ecological and economical importance. Plants defend themselves against insect herbivores through a variety of tolerance and resistance strategies. To date, few studies have systematically assessed the prevalence and importance of these strategies for root-herbivore interactions across different plant species. Here, we characterize the defense strategies used by three different grassland species to cope with a generalist root herbivore, the larvae of the European cockchafer Melolontha melolontha. Our results reveal that the different plant species rely on distinct sets of defense strategies. The spotted knapweed (Centaurea stoebe) resists attack by dissuading the larvae through the release of repellent chemicals. White clover (Trifolium repens) does not repel the herbivore, but reduces feeding, most likely through structural defenses and low nutritional quality. Finally, the common dandelion (Taraxacum officinale) allows M. melolontha to feed abundantly but compensates for tissue loss through induced regrowth. Thus, three co-occurring plant species have evolved different solutions to defend themselves against attack by a generalist root herbivore. The different root defense strategies may reflect distinct defense syndromes.