Response of the western pine beetle (Dendroctonus brevicomis) to variation in host phytochemistry

Variable defensive phytochemistry of pine trees may shape associated herbivore communities in a way that can drastically affect ecosystem properties. We sampled oleoresin from pines in Arizona across a landscape scale, and assessed monoterpene composition. From these data we identified four common phytochemical phenotypes in terms of relative monoterpene compositions. We introduced western pine beetles (Dendroctonus brevicomis) into host material of two phenotypes and assayed host selection, reproductive performance, and offspring fitness. Our experiments show that beetles differentially selected host phenotypes for constructing oviposition galleries. Interestingly, indicators of parent reproductive performance were not found to be consistent with host selection. Also, offspring fitness was not found to vary significantly across host tree phenotype. These results are partially consistent with previous studies by the authors that demonstrated a strong incidental effect of tree phenotype on bark beetle oviposition behavior. We are currently reciprocally transplanting offspring from each phenotype into new host material to determine if beetles select host phenotypes that correspond to their natal phytochemical environments.