Herbivore intraspecific variation and evolutionary divergence drive trophic cascade strength

Trophic cascades, the indirect effect of predators on non-adjacent lower trophic levels, are important drivers of the structure and dynamics of ecological communities. However, the influence of intraspecific trait variation on trophic cascade strength remains largely unexplored, which limits our understanding of the mechanisms underlying ecological networks. Here we experimentally investigated how herbivore intraspecific genetic variation and evolutionary divergence related to host-plant specialization influences trophic cascade strength in a terrestrial tritrophic system. We found that the occurrence and strength of the trophic cascade are strongly influenced by herbivore intraspecific variation and evolutionary divergence but are not associated with density-dependent effects mediated by herbivore population growth rate. Our findings stress the importance of intraspecific trait diversity and evolutionary adaptations as drivers of trophic cascade strength and underline that intraspecific variation should not be overlooked to decipher the joint influence of evolutionary and ecological factors on the functioning of multi-trophic interactions.