Abstract
Understanding species invasion is a central problem in ecology because invasions of exotic species severely impact ecosystems, and because invasions underlie fundamental ecological processes. However, the influence on invasions of phenotypic plasticity, a key component of many species interactions, is unknown. We present a model in which phenotypic plasticity of a resident species increases its ability to oppose invaders, and plasticity of an invader increases its ability to displace residents. Whereas these effects are expected due to increased fitness associated with phenotypic plasticity, the model additionally reveals a new and unforeseen mechanism by which plasticity affects invasions: phenotypic plasticity increases the steepness of the fitness surface, thereby making invasion more difficult, even by phenotypically plastic invaders. Our results should apply to phenotypically plastic responses to any fluctuating environmental factors including predation risk, and to other factors that affect the fitness surface such as the generalism of predators. We extend the results to competition, and argue that phenotypic plasticity's effect on the fitness surface will destabilize coexistence at local scales, but stabilize coexistence at regional scales. Our study emphasizes the need to incorporate variable interaction strengths due to phenotypic plasticity into invasion biology and ecological theory on competition and coexistence in fragmented landscapes.
Highlights
Understanding invasion of habitats by new species is a critical ecological problem due to the enormous impact invasive nonnative species are having on ecosystems worldwide [1,2,3,4]
When resident species were plastic, plasticity caused a steeper fitness surface that effectively acted as a barrier to invasion, even by invaders that were themselves plastic. These results suggest that phenotypic plasticity can strongly affect invasion biology, and we argue that the fitness surface–based mechanism invoked here has implications for competitive interactions in metacommunities
The results described above show how phenotypic plasticity of a resident species can effectively act as a barrier to invasion
Summary
Understanding invasion of habitats by new species is a critical ecological problem due to the enormous impact invasive nonnative species are having on ecosystems worldwide [1,2,3,4]. The ecological processes that affect an invader’s success are the same factors that affect the fitness of a resident species Both resident and invasive species (or populations) must balance risks of mortality and energy gain in the face of environmental variability, in which the densities of interacting species (e.g., resources, competitors, and predators) and abiotic environmental factors change due to both endogenously and exogenously driven factors [5]. Prey (animals and plants) from many taxa in disparate systems adaptively modify phenotype (e.g., behavior, life history, and physiology) in response to changes in variable biotic and abiotic factors [10,11,12] with profound effects on community structure and dynamics [15,16,17]
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