Niche-based mechanisms mediating the impacts and mitigation of biological invasion

Biological invasions drive species extinctions and population declines, prompting costly mitigation efforts. To evaluate and thereby improve the mitigation efforts, it is essential to understand the invasion process and the effects of the removal effort on the invading species. In this study, we use a trait- and niche-based theoretical approach to study such processes and mechanisms. We show that the degree of ecological specialisation of both the resident community and invading species, as well as the niche position of the invader, are key mediators of the negative impact of invasions. More specifically, generalist invaders tend to be particularly negative, especially when invading central niche positions of communities that are mainly composed of specialist species. Interestingly, our analyses also show that the optimal level of removal effort differs among diversity indices, emphasising that control programs should align their effort levels with clearly defined biodiversity objectives. Moreover, timing emerges as an important variable in mitigating potential negative effects. These results thus provide a fundamental understanding of the invasion process itself, the effect that ecologically different invaders may have when invading different types of communities, and how different degrees of removal effort can mitigate negative effects on the invaded community. Such an understanding can act as a stepping-stone for future efforts that aim to increase the effectiveness of human measures against biological invasion.