Effects of the diet on the microbiota of the Red Palm Weevil (Coleoptera: Dryophthoridae)

Rhynchophorus ferrugineus (RPW) is regarded as the major pest of palm trees. Although studies of the microbiota associated with this species have been performed in the last years, little attention has been dedicated to the influence of the diet in shaping the host bacterial community. Here, we investigated the influence of food sources (i.e. palm tissues vs apple based substrate) on the microbial diversity associated with RPW that was compared with the microbiota associated with wild individuals of the sister species Rhynchophorus vulneratus. The bacterial characterization was performed using a culture independent approach, i.e. the 16S rRNA pyrotag, and a culture dependent approach for a subset of the samples, in order to obtain bacterial isolates from RPW tissues. The bacterial community appeared significantly influenced by diet and temperature of locations where the animals were sampled. Proteobacteria resulted the most abundant clade and was shared by all the members of the three weevil examined groups. Within Proteobacteria, Enterobacteriaceae were identified in all the organs analysed, including hemolymph and reproductive organs. The apple-fed RPWs and of wild R. vulneratus showed a second dominant taxon within Firmicutes that was scarcely represented in the microbiota associated with palm-fed RPWs. A comparative analysis on the bacteria associated with the palm tissues, highlighted that 12 bacterial genera out of the 13 identified in the plant tissues were also present in weevils, thus indicating that palm tissues present a source for bacterial acquisition.