Climatic niche and range shifts of grey squirrels (Sciurus carolinensis Gmelin) in Europe: An invasive pest displacing native squirrels

BACKGROUNDAs an invasive pest from North America, grey squirrels (GSs; Sciurus carolinensis Gmelin) are displacing native squirrels in Europe. However, the climatic niche and range dynamics of GSs in Europe remain largely unknown. Through niche and range dynamic models, we investigated climatic niche and range shifts between introduced GSs in Europe and native GSs in North America. RESULTSGSs in North America can survive in more variable climatic conditions and have much wider climatic niche breadth than do GSs in Europe. Based on climate, the potential range of GSs in Europe included primarily Britain, Ireland, and Italy, whereas the potential range of GSs in North America included vast regions of western and southern Europe. If GSs in Europe could occupy the same climatic niche space and potential range as GSs in North America, they would occupy an area ca. 2.45 times the size of their current range. The unfilling ranges of GSs in Europe relative to those of GSs in North America were primarily in France, Italy, Spain, Croatia, and Portugal. CONCLUSIONOur observations implied that GSs in Europe have significant invasion potential, and that range projections based on their occurrence records in Europe may underestimate their invasion risk. Given that small niche shifts between GSs in Europe and in North America could lead to large range shifts, niche shifts could be a sensitive indicator in invasion risk assessment. The identified unfilling ranges of the GS in Europe should be prioritized in combating GS invasions in the future. (c) 2023 Society of Chemical Industry.

Automated summary

Grey squirrels from North America are displacing native squirrels in Europe but their climatic niche and range dynamics remain largely unknown. Through niche and range dynamic models, it was found that North American grey squirrels can survive in more variable climatic conditions and have a wider climatic niche breadth than European grey squirrels. If European grey squirrels occupied the same climatic niche space as North American grey squirrels, their potential range would be 2.45 times larger than their current range. The unfilling ranges of European grey squirrels compared to North American grey squirrels were primarily in France, Italy, Spain, Croatia, and Portugal. These findings emphasize the invasion potential of European grey squirrels and the importance of considering niche shifts in invasion risk assessment.