Utility of the CLIMEX ‘match climates regional’ algorithm for pest risk analysis: an evaluation with non-native ants in New Zealand

A fundamental question in biosecurity risk analysis is: Could the climate of a particular geographic region be suitable for the establishment of a potentially invasive species? Answers to this question can be sought by constructing species distribution models, which is often technically complex, time consuming, and uninformative for additional non-modelled species. A quicker, more broadly applicable approach involves using climate matching algorithms such as CLIMATCH and the ‘match regions’ function of CLIMEX (CLIMEX-MR). These algorithms generate indices of climatic similarity between different locations without reference to particular species. Several studies have shown the CLIMATCH algorithm provides biologically meaningful results, but the veracity of the CLIMEX-MR algorithm remains untested, despite its application in numerous published studies. We used CLIMEX-MR and high resolution New Zealand climate data to measure climatic similarities between New Zealand and the rest of the world. We then tested the veracity of the climatic match estimates by evaluating if their predictions regarding the suitability of New Zealand’s climate for 43 non-native ant species corresponded with empirical observations of those species in New Zealand. Non-native ants that are, or were once, established outdoors in New Zealand had overseas distributions that were climatically well matched with New Zealand. In contrast, species that either are established only indoors in New Zealand, or were observed to temporarily nest outdoors then die in New Zealand, had overseas distributions that were poorly matched. Species that are frequently intercepted in New Zealand, but are not established there, generally also had overseas distributions with low climatic similarities to New Zealand. We also measured climatic similarities between New Zealand’s 13 national parks and the rest of the world. The overseas distributions of the non-native ants showed poor climatic matches with New Zealand national parks, which is consistent with the absence of persistent outdoor non-native ant populations in those parks. Our results support the veracity of the CLIMEX match regions algorithm.