Symbiotic Associations of Bark Beetles

A vast community of organisms occurs on and within bark beetles and bark beetle-infested trees. The large diversity of symbiotic species covers a breadth of functional roles that are often redundant or substitutable. Symbiotic associations can be facultative or obligatory, and vary from antagonistic to mutualistic depending on the context at which the interactions occurs. Most symbiotic organisms are phoretic, and thus are transferred from tree to tree by bark beetles or other arthropods. Symbionts influence bark beetle communication, reproduction, nutrition and population dynamics, as well as tri-trophic interactions, competition among species, and host-tree utilization by bark beetles. Taxa considered symbiotic with bark beetles include fungi, bacteria, viruses, algae, mites, protozoa, and nematodes, among others. Interactions among symbionts are often mediated by host plant chemistry, abiotic factors such as temperature, or other phoretic organisms. Some of the symbionts, such as fungi, amplify our view of bark beetles as pests, as they may be tree pathogens or influence the coloration and texture of wood or plant products. However, some symbionts may also provide a solution to bark beetle population outbreaks and range expansion, as some symbiotic species are harmful to bark beetles and could be used as biological control agents.