PLANT FATTY ACIDS INFLUENCE BROOD DEVELOPMENT OF MOUNTAIN PINE BEETLE AND GROWTH OF ITS SYMBIOTIC FUNGUS: IMPLICATIONS TO HOST-RANGE EXPANSION OF AN HERBIVOROUS INSECT

Abstract

Nutritional composition of plants can affect the performance of insect herbivores and their associated microbial symbionts. Mountain pine beetle (Dendroctonus ponderosae) is an important bark beetle species that colonizes many species of Pinus within its historical range and encounter host species with different nutritional compositions. This insect has recently expanded its host range to jack pine (P. banksiana) forests, which is considered a novel host in terms of encounters with D. ponderosae. The nutritional aspects of selecting this new host are largely unknown. Here, I tested whether the recent host of D. ponderosae contains similar fatty acid concentrations as the beetle’s historical hosts and whether such similarity influenced the host expansion of D. ponderosae. I demonstrated that historical (lodgepole pine, P. contorta) and novel hosts are distinguished from a non-host (Populus tremuloides) species of D. ponderosae by concentrations of phloem fatty acids, such as linoleic and alpha-linolenic acids. Furthermore, the resulting information provides new insights into the biological roles of plant fatty acids in the survival of D. ponderosae larvae and establishment of the beetle’s symbiotic fungus, Grosmannia clavigera.