Print PageAfter over 50 years of intensive study on invasive species, there is no consensus about the mechanisms behind their success. When exotic species invade a new area, they leave behind their co-evolved communities and enter into new biotic interactions, which may be one of the major drivers of invasiveness. There is mounting evidence that exotic species interact with their invaded communities in novel ways, compared to in their native range or native species in their exotic range. However, altered biotic interactions for exotic species does not necessarily translate into increased performance and the potential to invade if the change in biotic interactions has minimal effects on invader fitness.
We conducted a meta-analysis with the goal of determining the fitness effects of altered biotic interactions during biological invasions. Our meta-analysis includes studies that test the fitness effects of key biological agents on exotic versus native species or on populations of exotic species verses populations in their native and introduced ranges. We predicted that invasive species would be less strongly affected by biotic interactions, compared to co-occurring native species, or conspecifics in their native range.
Results/Conclusions
While exotic species performance improved when herbivores were removed (24.0% increase in performance), meaning they are partially controlled by these biotic agents, native species benefitted more than twice as much (53.7%), indicating native species fitness is controlled to a much greater degree by herbivory. For other biotic interactions, such as predation and mutualism, exotic and native species were affected in similar ways. Both groups of species were harmed by the removal of mutualists (67% reduction in performance), and benefitted from the removal of predators (12% increase in performance). Our results indicate that biotic interactions change during the process of invasion, and may be responsible for the success of exotic species.
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