Herbivore-induced changes in fruit-frugivore interactions

1. Herbivore attack can induce dramatic changes in plant chemical defences. These responses protect plants against future herbivory, but can also have important physiological and ecological costs. Ecological costs of defence have received recent theoretical attention; however, many proposed costs have not yet been demonstrated empirically. In particular, field data are lacking as to whether induced responses in leaves can lead to correlated changes in fruit palatability that reduce fruit removal by mutualist seed dispersers. 2. Using the tropical shrub, Hamelia patens (Rubiaceae), we examined changes in fruit removal, palatability and maturation time following various treatments to the subtending leaves, including herbivory, mechanical damage and/or application of methyl jasmonate (MeJA). 3. Fewer fruits were removed from herbivory- and MeJA-treated branches than from controls, and results from three bioassays with ants and fungi suggested that this response was mediated by changes in fruit palatability. In addition, fruits from MeJA-treated branches matured more quickly than those from control branches. 4. Synthesis. Taken together, our results provide novel evidence that induced responses to herbivory can affect fruit-frugivore interactions through two mechanisms: changes in fruit palatability and changes in fruit development time. This highlights the importance of physiological linkages between leaf and fruit traits in determining the overall costs of plant defence and the fitness outcomes of multispecies interactions.