Transgenerational consequences of plant responses to herbivory: An adaptive maternal effect?

Herbivory has many effects on plants, ranging from shifts in primary proces ses such as photosynthesis, growth, and phenology to effects on defense aga inst subsequent herbivores and other species interactions. In this study, I investigated the effects of herbivory on seed and seedling characteristics of several families of wild radish (Raphanus raphanistrum) to test the hyp othesis that herbivory may affect the quality of offspring and the resistan ce of offspring to plant parasites. Transgenerational effects of herbivory may represent adaptive maternal effects or factors that constrain or amplif y natural selection on progeny. Caterpillar (Pieris rapae) herbivory to gre enhouse-grown plants caused plants in some families to produce smaller seed s and those in other families to produce larger seeds compared with undamag ed controls. Seed mass was positively associated with probability of emerge nce in the field. The number of setose trichomes, a putative plant defense, was higher in the progeny of damaged plants in some families and lower in the progeny of damaged plants in other families. In a field experiment, pla nt families varied in their resistance to several herbivores and pathogens as well as in growth rate and time to flowering. Seeds from damaged parent plants were more likely to become infested with a plant virus. Although her bivory on maternal plants did not directly affect interactions of offspring with other plant parasites, seed mass influenced plant resistance to sever al attackers. Thus, herbivory affected seed characters, which mediated inte ractions between plants and their parasites. Finally, irrespective of seed mass, herbivory on maternal plants influenced components of progeny fitness , which was dependent on plant family. Natural selection may act on plant r esponses to herbivory that affect seedling-parasite interactions and, ultim ately, fitness.