Conclusion and perspectives
Warming and eutrophication are expected to alter the dynamics and simplify the structure of larger food webs (Brose et al. 2012), facilitating species invasions and increasing their impact on invaded systems (Sentis et al. 2021). We have shown how body size and trophic position determine the fate of species invasions and that species invasions can mitigate or amplify the negative effects of environmental stressors on local communities. Our predictions showed that smaller species are particularly likely to invade communities in warmer, nutrient-limited environments, while communities facing cold temperatures and nutrient enrichment are vulnerable to invasions by larger predators. Invaders can also fill vacant niches when resident species disappear. For example, the predicted poleward shift of smaller zooplankton species may benefit warming Arctic habitats (Evans et al. 2020). Invading predators may also buffer local communities against eutrophic effects at lower temperatures (as in Hughes et al. (2013)). Therefore, invasive species may not always need to be eradicated or controlled (Simberloff 2009; Glen et al. 2013), especially if the associated costs are too high. On the other hand, our findings support active management and eradication of invaders with negative impacts on local communities, including those that destabilise local communities such as small consumers in cold, nutrient-rich habitats (Robertson et al. 2020). Overall, we predict that species invasions may contribute to the downsizing of food webs (Young et al. 2016), as successful invaders will include smaller competitors and comparatively small predators.
Acknowledgements: This research was supported by the Grant Agency of the Czech Republic (Grant no. 21-29169S). NAP was supported by the University of Oulu and the Academy of Finland Profi4 Grant 318930 Arctic Interactions (ArcI). AS was supported by the ANR project EcoTeBo (ANR-19-CE02-0001-01) from the French National Research Agency (ANR). Computational resources were supplied by the project “e-Infrastruktura CZ” (e-INFRA CZ ID:90140) supported by the Ministry of Education, Youth and Sports of the Czech Republic. The authors have no conflict of interest to declare.