Tracing the dispersal route of the invasive Japanese beetle Popillia japonica

Abstract The Japanese beetle, Popillia japonica, is a highly polyphagous Scarabeidae native to Japan that colonized North America and Azores in the last century and has recently invaded Italy and Switzerland. Considering its economic impact to the horticulture and turfgrass industries, this species was ranked within the EU priority pests list in 2019. In order to reconstruct the source of introductions of this pest, we investigated the genetic variability of P. japonica in its native and invaded areas worldwide by analyzing 9 microsatellite loci and two mitochondrial genes, COI and CytB. There are two populations of Japanese beetles, from a limited area within central Japan, that are likely the source of the North American population. Moreover, the microsatellite data and resulting phylogeographic reconstruction suggests that the two European populations originated from independent introductions from southeast (Azores) and northeastern (Italy and Switzerland) North America (1). (1) For simplicity, in this paper North America refers to Canada and USA