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Abstracts - Guilherme Pinheiro

EFFECTS OF INDUCED PLANT DEFENSES ON THE ASSOCIATED COMMUNITY OF ARTHROPODS IN A NATURAL SYSTEM


Guilherme Pinheiro1*, Thaís Silveira1, Gustavo Romero1 and Mônica Kersch-Becker1,2


1 Department of Animal Biology, University of Campinas, Campinas-SP, Brazil 2 Department of Biological Sciences, University of Alabama, Tuscaloosa-AL, USA; monikersch@gmail.com
* Correspondence: pinheiro.gperez@gmail.com


Plants actively defend themselves against herbivores and pathogens via constitutive defenses (level of defenses of an undamaged plant) or induced defenses (any defense induced after damage). Both constitutive and induced plant defenses can have a profound impact on the composition and organization of ecological communities through biochemical changes in the jasmonic acid and salicylic acid pathways. These two phytohormones may induce direct and indirect defenses, by conferring resistance against herbivores and recruiting the natural enemies, respectively. The jasmonic acid pathway often induces defenses against chewers. In contrast, the salicylic acid pathway induces resistance against sap-sucking insects and pathogens. This study explored the effects of chemical elicitors, which stimulate the jasmonic acid and salicylic acid pathways in plants, on the associated community of arthropods in a natural system. We carried out the experiments in the Serra do Japi Biological Reserve, Jundiaí-SP. We used 69 individuals of Trichogoniopsis adenantha (DC) (Asteraceae), a small perennial shrub associated with a rich community of arthropods. We randomly assigned each plant to one of the following treatments: (i) Control (distilled water + acetone), (ii) MeJA (1.0mM of methyl jasmonate + acetone) to stimulate the induction of the jasmonic acid pathway and (iii) BTH (1.2mM of benzo(l,2,3)thiadiazole-7-carbothioic acid(S)-methyl ester + acetone) to induce the salicylic acid pathway. We applied the treatments and recorded the abundance and richness of arthropods on T. adenantha weekly from April/2015 to August/2016. On a separate experiment we applied the same treatments once to 4-month old plant and quantified the concentration of pyrrolizidine alkaloids seven days later. The proportion of arthropod guilds differed among treatments, chewers were more abundant on BTH-sprayed plants while sap-sucking insects and natural enemies were more abundant on MeJA-sprayed plants. The concentration of pyrrolizidine alkaloids was higher on flowers and flower buds and MeJA-sprayed plants induced pyrrolizidine alkaloids in all tissues of the plants.These results demonstrated the importance of induced plant defenses in determining the abundance of arthropods and structuring ecological communities in natural systems.