Successful Invasions and Failed Biocontrol: The Role of Antagonistic Species Interactions

Abstract

Understanding the successes and failures of nonnative species remains challenging. In recent decades, researchers have developed the enemy release hypothesis and other antagonist hypotheses, which posit that nonnative species either fail or succeed in a novel range because of the presence or absence of antagonists. The premise of classical biological control of invasive species is that top-down control works. We identify twelve existing hypotheses that address the roles that antagonists from many trophic levels play during plant and insect invasions in natural environments. We outline a unifying framework of antagonist hypotheses to simplify the relatedness among the hypotheses, incorporate the role of top-down and bottom-up influences on nonnative species, and encourage expansion of experimental assessments of antagonist hypotheses to include belowground and fourth trophic level antagonists. A mechanistic understanding of antagonists and their impacts on nonnative species is critical in a changing world.

Effect of Drosophila suzukii on Blueberry VOCs: Chemical Cues for a Pupal Parasitoid, Trichopria anastrephae

“…In a broader sense, studies on these local parasitoid populations at the regional level may offer opportunities to manage SWD in Latin America without new introduction of exotic species. Hence, a nonnative organism such as SWD in Latin America may become controlled by a regulating mechanism in the introduced range, which limits its density and expansion (Schulz et al 2019).…”

Eradicating the large white butterfly from New Zealand eliminates a threat to endemic Brassicaceae

“…Nelson's topography probably also helped to reduce emigration rates because ocean lies to its northwest, the mountains to its east contained few host plants, and arguably the sole benign pathway for natural dispersal was across the agricultural plains to its south. Moreover, the abundant and diverse P. brassicae natural enemies in New Zealand might have reduced the chance that emigrants could found new populations due to biotic resistance [76][77][78].…”

The Hierarchy-of-Hypotheses Approach: A Synthesis Method for Enhancing Theory Development in Ecology and Evolution

“…In addition, the nested, hierarchical structure invites looking for connections upward: Figure 4 shows the escalation hypothesis as one variant of an even broader hypothesis, positing that “Species interactions direct evolution.” This in turn can enhance the future search for patterns and mechanisms across unconnected study fields. A respective example can be found in Schulz and colleagues ( 2019 ). In that article, the authors used the HoH approach to organize twelve hypotheses each addressing the roles that antagonists play during species invasions.…”