Chemical communication strategies of Capnodis tenebrionis (L.) (Coleoptera: Buprestidae): ecological implications for intraspecific and host interactions

This study focuses on several aspects of communication strategies adopted by adults of the Mediterranean flat-headed root-borer Capnodis tenebrionis (Coleoptera: Buprestidae). Morphological studies on the structures involved in mate recognition and acceptance revealed the presence of porous areas in the pronota in both sexes; these areas were variable in shape and size, but proportionally larger in males. Moreover, the presence of chaetic, basiconic and coeloconic sensilla in the antennae of both males and females was verified. Bioassays revealed stereotyped mating behavior in males, and, in females, the presence of pronotal secretions in mate recognition and acceptance. During the mating assays, the females pronotum was covered by a biologically inert polymeric resin (DenFilTM), which prevented males from detecting the secretions and allowed for the collection of chemical compounds. Preliminary GC-MS analysis of the resin suggested it may be used to retain compounds from insect body surfaces, and revealed sex-specific chemical profiles in the cuticles. Since adult Capnodis tenebrionis may use volatile organic compounds (VOCs) emitted from leaves or shoots for short-distance orientation, the VOC emission profiles of apricot trees were characterized; several volatiles related to plant-insect interactions involving fruit tree species of the Rosaceae family and buprestid beetles were identified. To improve understanding of how VOCs are perceived, candidate proteins involved in chemoreception (odorant-binding proteins and chemosensory proteins) were identified using tissue and sex-specific RNA-seq data. The implications for chemical identification, physiological and ecological functions in intraspecific communication and insect-host interactions are discussed and potential applications for monitoring presented.