Specificity of plant-insect interactions: volatile and non-volatile responses of Piper species induced by weevil attack

Recent studies suggest that the biodiversity of an ecosystem is correlated to the richness in plant species. This correlation is clearly evidenced in quantitative terms, given that plants are the primary producers (i.e. the more energy, the more organisms a system can support). However, it is less understood in qualitative terms, that is to understand the functional diversity of how species interact and what makes them functionally exclusive and unique. Here we study the chemical basis of how weevil herbivores of the Atlantic Forest exploit different plant species of Piper, as well as the level of specialization of such interactions. A small collection of weevils which occur in Piper species is currently being built, identified, and described for anatomy and sexual dimorphism. So far, at least three weevil species were found in four different collection sites in São Paulo State: Peridinetus zinckeni, Ambates sp., and Vossius sp. Among these, P. zinckeni is the most frequently found weevil associated with Piper sp. In nature, P. zinckeni seems to have a preference towards P. gaudichaudianum, and, even within the same plant species, it is observed that P. zinckeni tends to occur in P. gaudichaudianum individuals that were not attacked by larvae of Eois sp. – a specialist herbivore of Piperaceae. To test whether there are differences in inter- and intraspecific attractiveness of Piper sp. to P. zinckeni we performed two experiments where we measured the herbivore damage as well as collected plant-derived samples to analyze the herbivore-induced responses. In a field experiment, we assigned P. gaudichaudianum individuals as attractive or non-attractive according to the presence or absence of P. zinckeni foliar damage traces. We bagged local, systemic adjacent and systemic distal leaves of plants with or without P. zinckeni individuals previously collected in the same site, and that were starved for 3 days prior to the experiment. Photos of the leaves were taken to digitally quantify the leaf area loss; and volatile blends and leaf tissue were sampled and are currently under analysis by GC-MS and HLPC-DAD, respectively. An additional greenhouse experiment was performed under similar experimental manipulation, but in which we compared potted individuals of P. gaudichaudianum and P. malacophyllum – two naturally co-occurring Piper species. We predict that the preference loosely observed in the field will reflect in different levels of herbivore damage and/or distinct profiles of volatiles and non-volatiles produced in response to P. zinckeni attack.