Using semiochemicals to predict biotic resistance and facilitation of invading phytophagous insects

Invasive species are leading causes of biodiversity loss and economic
damage. Allocating limited resources towards prevention and management of
invasions requires risk assessments based on ecological knowledge for
species of potential concern. Interactions of potentially invasive species
with heterospecifics in a novel community will contribute to biotic
resistance and facilitation experienced by the invader, and thus the
likelihood of establishment. To experimentally predict heterospecific
interactions, we conducted field experiments using synthetic
aggregation-pheromone lures to measure the response of ecologically
relevant species (possible predators, competitors, and facilitators) to
the simulated presence of two potentially invasive spruce bark beetles,
the North American Dendroctonus rufipennis (tested in Norway) and the
European Ips typographus (tested in eastern Canada). The Canadian beetle
community responded strongly to I. typographus lures, suggesting potential
for considerable biotic resistance, whereas D. rufipennis lures prompted
little response by the Norwegian beetle community. D. rufipennis was
attracted to I. typographus lures, suggesting potential facilitation
between these species through cooperative mass attack on trees. Our
findings will inform invasive-species risk assessments for I. typographus
and D. rufipennis and highlight useful methods for assessing interactions
among other taxa that rely heavily on semiochemical communication.