Forecasting the potential distribution of invasive leafminer pests, Liriomyza spp. (Diptera: Agromyzidae), and their natural enemies

Three species of polyphagous Liriomyza leafminers (Diptera: Agromyzidae), Liriomyza huidobrensis, L. sativae, and L. trifolii, are internationally significant pests of vegetable and nursery crops that have each been recently detected on the Australian mainland. Due to the early stages of these invasions in Australia, it is unclear how climatic conditions are likely to support and potentially restrict the distribution of these species as they expand into novel ranges and threaten agricultural production regions. Additionally, it is unclear how natural enemies, particularly parasitoid wasps, will mitigate the impacts of these pests. Here, we predicted the future establishment potential of L. huidobrensis, L. sativae and L. trifolii in Australia, as well as two cosmopolitan parasitoid wasps known to provide control of the flies in both field and glasshouse settings, Diglyphus isaea (Hymenoptera: Eulophidae) and Hemiptarsenus varicornis (Hymenoptera: Eulophidae). Global distribution data spanning 42 countries were compiled and used to validate a process-based model of establishment potential based on intrinsic population growth rates. The modelling approach successfully captured the international distribution of the three Liriomyza species based on environmental variables and predicted the high suitability of non-occupied ranges in Australia. The largely unfilled climatic niche available to these pests demonstrates the early stages of their Australian invasions and highlights locations where vegetable production regions are at particular risk. In addition to Australia, our results highlight many regions globally where L. sativae, L. trifolii and L. huidobrensis have the potential to spread in the future. Within Australia, D. isaea and H. varicornis are predicted to have a large spatial and seasonal overlap with each Liriomyza species and thus are expected to influence the future spread of these pests and play an important role in local pest management programs.