Factors influencing establishment success of insect and weed biological control introductions in Hawaiʻi

Predicting the likelihood of establishment, or naturalization, of species in new environments is complex, but could prove particularly useful in biological control research and implementation. Things like competition with extant species and number of releases made are potentially important mediators of the establishment process. Insects introduced for biological control in Hawaiʻi provide a unique opportunity to study the impact of these factors as records of attempted introductions and establishment are reasonably complete. Here, we analyze the establishment rate of insect and weed biological control agents purposefully introduced to Hawaiʻi over the past century to determine the potential roles played by hosts and competitors present in the environment on the success of establishment of these introduced species. Historic release and establishment records maintained by the Hawaiʻi Department of Agriculture were used, while data on host range, types of hosts attacked in Hawaiʻi, and introduction history of alternative pest hosts and indigenous species attacked in Hawaiʻi were obtained from literature sources. Preliminary analyses show that a higher number of related species in the environment negatively impacted the likelihood of establishment for insect biocontrol but not weed biocontrol agents. Further analyses will help to determine important ecological attributes of potential biological control agents that should be considered when planning future introductions.