The spread of invasive species is a global environmental problem that generates large societal and ecological costs. There is large variation between different natural communities in their susceptibility to invasion, and despite a long history of research in this area we still lack an empirically based understanding of the mechanisms underlying this variation.
In this project we use information about introductions of exotic fish species to lakes to examine what properties of ecological communities that make them resistant to invasive species. The project will generate knowledge that can be used in management, e.g., to identify lakes that are particularly susceptible to invasion by exotic fish species, but it will also contribute to the development of general theory within this field.
To develop an empirically verified theory for biotic resistance, i.e., a theory that can be used to predict how well ecological communities resist invasive species.
1. Biotic resistance of an ecological community is determined by its species richness.
2. Biotic resistance is determined by the saturation of the community, i.e., the number of species relative to the maximum number of species that can coexist.
3. Resident species vary in their contribution to resistance. An estimate of saturation should therefore be based on a weighted sum of the number of species, where the weight for each species describes its contribution to the resistance.
4. Invading species vary in their responses to habitats and resident species.
Information about >1200 introductions of fish species in lakes are used to test these hypotheses.