Temperature interacts with jack pine host defences to influence the growth of mountain pine beetle‐associated fungi

Abstract During the recent outbreak in western Canada, mountain pine beetle (MPB) Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae) and its associated fungi expanded their geographic and host ranges to include jack pine, Pinus banksiana Linnaeus (Pinaceae), in the boreal forest. While previous research indicates that MPB and its symbiotic fungi can infest and induce chemical host defences in jack pine, it is uncertain how jack pine defences will impact MPB‐associated fungi, particularly under novel climatic conditions. We investigated the growth response of the three known MPB fungal symbionts ( Grosmannia clavigera (Robinson‐Jeffrey and Davidson), Ophiostoma montium (Rumford) and Leptographium longiclavatum (Lee, Kim and Breuril)) in media amended with constitutive and fungal symbiont‐induced jack pine monoterpene profiles from jack pine at three temperatures (18, 23 and 30°C). While the impact of host monoterpene defence profile on fungal growth only marginally varied between temperatures there were significant effects of temperature on optimal growth of fungal species. Fungal growth was facilitated by host monoterpene profiles induced by other species of MPB‐associated fungi, suggesting indirect host‐mediated interspecific interactions between MPB fungal symbionts that may assist in maintaining redundant symbioses. Since the species forming the community of symbiotic fungi have different requirements regarding both optimal temperature ranges and host monoterpene composition, the ongoing climate change may alter the suitability of jack pine as a host, potentially impacting the establishment of MPB populations in these forests.