Resident Parasitoids and Biotic Resistance to Invasive Species in Hawaiʻi, and Implications for Biological Control Programs

Hawai'i is subject to disproportionately high rates of biological invasion, including adventive insects. These alien species have been the targets of numerous biological control efforts. The contribution of native species preventing adventives from becoming invasive has received little attention. We analyzed numbers of invasive species utilized by native parasitoids, showing that resident natural enemies infrequently attack alien species, but in some cases, exert significant population control. Purposefully introduced biological control agents likely also contribute to mitigating new invasions. Certain taxa, such as Coleoptera, should be considered priority targets for importation biological control, as they appear highly unlikely to accumulate resident natural enemies.