Range expansion of an invasive species through a heterogeneous landscape - the case of American mink in Scotland

© 2015 John Wiley & Sons Ltd. Aim: The impact of invasive species is one of the main causes of biodiversity loss world-wide, and as a result, there is much interest in understanding the pattern and rate of expansion of species outside their native range. We aimed to characterize the range expansion of the American mink (Neovison vison) invading from multiple introduction points through a varied landscape bounded by coastline to better understand and manage its spread. Location: Scotland, UK. Method: We collated and used records of mink presence to calculate the historical range and rate of range expansion at successive time intervals. We used a presence-only model to predict habitat suitability and a newly developed individual-based modelling platform, RangeShifter, to simulate range expansion. Results: Records showed that mink were distributed throughout Scotland, except in the far north. We found that the rate of spread varied both spatially and temporally and was related to landscape heterogeneity. Habitat suitable for mink in west Scotland is restricted to the coast. Main conclusions: We concluded that temporal and spatial variation in range expansion is attributable to heterogeneity within the landscape and also demonstrated that the potential for long-distance dispersal does not necessarily facilitate range expansion when availability of suitable habitat occurs in narrow strips and/or is fragmented. We have highlighted methodological gaps in calculating rates of expansion in invasive species but have demonstrated alternative methods that successfully utilize presence-only data. Our study reaffirms that invasive species will colonize less favourable habitats and highlights the need to remain vigilant of their potential for expansion even when distribution appears to be static for a time.