Ontogenetic trajectories in plant defenses and nutritional quality cascade to alter tri-trophic interactions

QUINTERO, C.; LAMPERT, E. C.; BOWERS, M. D.

Buenos Aires

Simposio; 32nd New Phytologist Symposium: Plant interactions with other organisms: molecules, ecology and evolution; 2013

The New Phytologist Trust

Plant-herbivore-natural enemy interactions vary markedly in space and time. However, studies assessing changes in the direction and magnitude of these interactions have traditionally examined the role of spatial variation more than the role of temporal change. Using four ontogenetic stages of Plantago lanceolata (Plantaginaceae) and the specialist herbivore Junonia coenia (Nymphalidae), we showed that increasing leaf physical and chemical defenses but decreasing nutritional quality with age significantly influenced all species interactions. Female butterflies showed a strong oviposition preference for younger stages of P. lanceolata over older ones and caterpillars feeding on those juvenile plants showed faster relative growth rate and increased digestive efficiency than those feeding on reproductive stages. The implications to the third trophic level also vary since caterpillars feeding on younger stages acquired lower levels of sequestered chemical defenses, which could render them: (i) more susceptible to predation due to low unpalatability, but (ii) more resistant to parasitoids due to its higher ability to mount an immune response against simulated parasitoid eggs. These results demonstrate that plant ontogeny can strongly alter tri-trophic interactions both directly and indirectly, emphasizing the importance of plant ontogenetic trajectories in regulating temporal shifts in herbivore population dynamics and community structure.