Abstract:
Exotic insects can have a range of ecological, economic and social impacts in a new area. Preventing an unwanted species from establishing is the best long-term management option as eradication is very costly and often impossible once establishment is achieved. This study examines: i) the taxonomic composition of all exotic insect species accidentally introduced into New Zealand, and ii) the spatial and temporal distribution of establishment for these species. The first recorded location and date of arrival for each exotic species served as proxies for establishment, and were obtained from the Ministry of Primary Industries, literature searches, and specimen examination at the New Zealand Arthropod Collection. Spatial and temporal data was analysed with regression trees, using a binary recursive partitioning approach against a range of quantifiable factors that define a particular location or time period which may have affected establishment (e.g. disturbance, propagule pressure, biogeography, search effort). As of December 2015, 1477 exotic insect species have successfully established in New Zealand across 16 orders, 234 families and 1017 genera. Coleoptera is the largest order and Aphididae (Hemiptera) is the largest family established. Regions with the highest number of exotic species first established were Auckland (448 species, 40.4%), and Nelson-Tasman (143 species, 12.9%). The lowest number occurred in the West Coast of the South Island (6 species, 0.54%). The number of tourists is the primary factor explaining spatial patterns of exotic insect establishment followed by exotic vegetation land cover. Gross domestic product best explained the temporal patterns of establishment, indicating variables associated with human disturbance have a key influence on the number of species establishing into New Zealand over time. The current trajectory from the 1980’s indicates less species are establishing, and suggests biosecurity efforts may be effective at reducing rates of establishment. Analyses of very large numbers of species has allowed a better understanding of what factors enable new insect species to successfully establish. This will enable targeted sampling efforts and improve management practises; ultimately reducing the number of potentially invasive insect species establishing in New Zealand. KEY WORDS Biological invasions, biosecurity, disturbance, detection, establishment, exotic insects, globalisation, invasive species, propagule pressure.