 Since the mid-1980s, the population of "P. dominula" has expanded to rather cooler regions, especially towards northern Europe.Global warming is speculated to have raised temperatures of certain areas, allowing "P. dominula" to expand to originally cooler regions.The first North American occurrence of "P. dominula" was reported in Massachusetts in the late 1970s, and by 1995, this species had been documented throughout the northeastern USA.