The Japanese beetle (Popillia japonica) is a severe invasive insect pest of turf, landscapes, and horticultural crops. Originally from Japan, this insect has successfully colonized much of the United States over the last hundred years and has recently established in mainland Europe. With over 300 reported host plants, this highly polyphagous insect thrives in both urban and agricultural landscapes. Climate change is expected to exacerbate agricultural losses from the Japanese beetle by lengthening its growing season and altering its potential geographic distribution. In this study, a process-oriented bioclimatic niche model for P. japonica was developed using CLIMEX, to examine its potential global distribution under both current climatic conditions and possible future climate under the RCP 8.5 emission scenario for the year 2050. Simulated changes in its life cycle duration (voltinism) were also examined.
Results/Conclusions
The CLIMEX model was validated with independent widespread distribution data in its non-native US range, as well more limited data from Europe. Under current climatic conditions, the bioclimatic niche model agreed well with all credible distribution data. Model projections indicate a strong possibility of further range expansion throughout mainland Europe under both current and future climates. In North America, projected increases in temperature would enable northward range expansion across Canada while simultaneously shifting southern range limits in the United States. In Europe, the suitable range for P. japonica would increase by 23% by mid-century, especially across portions of the UK, Ireland, and Scandinavia. Under the RCP 8.5 scenario, cumulative growing degree-days increased, thereby reducing the probability of bi-annual life cycles in northern latitudes where they can occur, including Hokkaido, Japan, northeastern portions of the United States and southern Ontario, Canada. The results of this study highlight several regions of increasing and emerging risk from P. japonica that should be considered routinely in ongoing biosecurity and pest management surveys.