Temperature-dependent effects on mutualistic, antagonistic, and commensalistic interactions among insects, fungi and mites

The relative abundance and nature of associations between symbiotic species can be affected by abiotic conditions with consequences for population dynamics. We investigated the effects of temperature on the community of mites and fungi associated with the southern pine beetle, Dendroctonus frontalis, an important pest of pine forests in the southern United States. First, we determined whether the growth rates of mutualistic and antagonistic fungi associated with D. frontalis differed in their responses to temperature. Second, we tested the effects of temperature on the abundance of, and interactions among, fungi, mites and beetles within D. frontalis-infested trees. Fungi differed in their growth responses to temperature, resulting in changes in fungal-beetle associations. Mite species associated with D. frontalis also differed in their responses to temperature, resulting in different mite communities associated with bark beetle progeny. The effects of temperature on beetle reproduction could not be assessed because of high wood borer density, but inter-relations among surviving beetles, mites and fungi were altered by temperature. Results support the hypothesis that temperature can produce direct and indirect effects on the web of mutualistic and antagonistic relationships within the community of D. frontalis and their symbiotic mites and fungi.