Using chemical ecology to predict establishment risk of non-native insects

Invasive species are a rising global concern, with the potential to cause serious economic and ecological damage. Preventing or mitigating future establishments of non-native and potentially invasive species is best done by allocating the limited resources available towards the species that pose the greatest risk. Among the many determinants of risk are the abilities of an introduced species to establish, which is influenced in part by ecological interactions with native species, e.g., predation and facilitation. Predicting these interactions may be very difficult, however, in cases where native and non-native species have yet to come into contact. Our research focused on two species of spruce bark beetles, one native to North America (Dendroctonus rufipennis), and another to Europe (Ips typographus), which may become invasive in the range of the other. By using beetle pheromones as a proxy for the presence of a non-native species, we were able to assess the responses of predators and competitors and use them as a basis for predicting ecological interactions between live insects. We found that D. rufipennis may avoid a degree of competition and predation by being semiochemically inconspicuous in Europe, and that both species may facilitate each other by cooperating in mass attacks. We propose that similar methods can be used for other species that rely heavily on chemical communication, and that the results may be of considerable value for invasive species risk assessments.