Contributions by Host Trees and Insect Activity to Bacterial Communities in Dendroctonus valens (Coleoptera: Curculionidae) Galleries, and Their High Overlap With Other Microbial Assemblages of Bark Beetles.

Bark beetles are associated with a diversity of symbiotic microbiota that can mediate interactions with their host plants. Dendroctonus valens LeConte is a widely distributed bark beetle in North and Central America, and initiates solitary attacks on several species of Pinus in the Great Lakes region. In this study, we aimed to further characterize the bacterial community associated with D. valens feeding galleries using next-generation sequencing, and the possible contributions of both tree-resident and insect-associated bacteria to these consortia. We found that D. valens galleries harbor a diversity of microbial associates. Many of these associates were classified into a few taxonomic groups, of which Gammaproteobacteria were the most abundant class. Of the Gammaproteobacteria detected, many formed clades with 16S-rRNA sequences of bacteria previously associated with D. valens Many of the bacteria sequences detected in the galleries were similar to bacteria that function in detoxification, kairomone metabolism, and nitrogen fixation and cycling. The abundance of bacteria in galleries were 7× and 44× higher than in the surrounding uninfested tissues, and that were not attacked by D. valens, respectively. This suggests that the bacteria present in beetle galleries are largely introduced by D. valens and proliferate in this environment.