Outnumbering all other non-native animals, insects are extremely successful invaders, with more than 7,000 species established outside their native range. Insects are often introduced accidentally alongside ornamental plants, prompting the hypothesis that plant introductions may predict insect invasions.
Analysing records of 16,000 insect establishments and 54,000 plant naturalizations derived from GBIF-mediated occurrences and other sources, researchers tested this hypothesis using generalized linear mixed models. In their analysis, they investigated the predictive power of several candidates for the ability to explain current insect flows between biogeographical regions.
Comparing early and late introductions, they found that the current distribution of non-native insects was more correlated to the distribution of nonnative plants from 1900 than 2010, suggesting that plant introductions preceed insect invasion by an extensive time lag. They also found that plant naturalizations were a better predictor of insect invasions than the flows of both plant trade and general trade.
Based on the observed time lag between plant and insect flows, the authors estimated a global debt of 3,442 insect introductions—an increase in potential invasions of 35 per cent in a near future. The significance of this debt was largest in the Afrotropics, the Neotropics and Indomalaya, where their analysis predicted an expected 10 to 20-fold increase in nonnative insect discoveries.
With evidence of a strong link between plant and insect invasions, the study highlights the importance of limiting the spread of nonnative plants in order to prevent future insect introductions and their potentially devastating impacts on both ecosystems and human societies.