Establishment patterns of non-native insects in New Zealand

Abstract

Insects comprise the majority of non-native animal species established around the world. However, geographic biases in knowledge hamper an overall understanding of biological invasions globally. A dataset of accidentally introduced non-native insect species established in New Zealand was compiled from databases, entomological literature, and examination of specimens in the New Zealand Arthropod Collection. For each non-native species, the first recorded location and first recorded date of detection was obtained. Excluding intentionally introduced species, there are 1477 non-native insect species successfully established in New Zealand across 16 orders, 234 families and 1017 genera. Four orders (Coleoptera, Hemiptera, Hymenoptera and Diptera) contributed 77.5% of all established insect species. Herbivores represented the largest feeding guild (47.7%), comprised of polyphagous (48.3%) or oligophagous (39.7%) species. The majority of these species originated in the Australasian (36.7%) and Palearctic regions (24.8%). Regression trees, using a binary recursive partitioning approach, found the number of international tourist arrivals, exotic vegetation cover, and regional gross domestic product were the main factors explaining spatial patterns of recently established species. Gross domestic product best explained temporal patterns of establishment over the last century. Our findings demonstrate that broad-scale analyses of non-native species have important applications for border biosecurity by providing insight into the extent of invasions. In New Zealand, the current trajectory indicates fewer non-native species are establishing annually, suggesting biosecurity efforts are being effective at reducing rates of establishment.