Evaluating the effect of American mink, an alien invasive species, on the abundance of a native community: is coexistence possible?

Loss of biodiversity due to biological invasions is one of the most critical issues our society is facing. American mink is one of the most nefarious invasive non-native species and has major consequences for diversity, ecosystems and economics. A project to evaluate the impact of American mink has been carried out in Catalonia since 2000 under the aegis of regional and national government and a European LIFE programme. In this study, we tested whether temporal variations in the relative abundance of native species were related to American mink. In addition, we compared the abundance of natives before and after mink arrival. Among the competitors spotted genet and European polecat, mink abundance and arrival had a significant negative effect on their populations. However, among black rat and fish prey only three native fish species had a negative temporal relation with the abundance of mink and three fish species showed a significant difference in their abundance before and after mink arrival. The effect of mink was significant among species with a higher niche overlap (polecat and genet versus mink). The persistence and coexistence of the alien and native species seems to depend on heterogeneity, in terms of the based on niche segregation among these species.