The causes and consequences of temporal variation in the abundance of organisms constitute a central theme in ecological inquiry. Rapid evolution can occur over ecological time scales, potentially resulting in altered temporal variation in abundance and complicating inferences about the consequences of temporal variation. We used 2-species models to generate predications about the effects of evolution on temporal variation of species’ abundances in competitive and predator-prey interactions. We then assessed whether evolution altered the temporal variability in species’ abundances by comparing founder populations and their evolved descendants in experimental communities of ciliates and rotifers following invasion by a novel species. Models suggest that 1) populations of species that evolved improved competitive ability will experience increased variability in abundance with increasing population size, while populations of inferior competitors will experience decreased abundance and variability in abundance, and 2) if evolution results in higher attack rates, predators will exhibit decreased abundance and slightly decreased temporal variability in abundance, and prey will exhibit decreased abundance and increased temporal variability in abundance. We used ANOVA and MANOVA to assess the effect of evolution on dynamics.
Results/Conclusions
Differing evolutionary histories resulted in significant differences among treatments in abundances and temporal variation in abundances of both resident and invading species. Naïve invaders in communities with experienced residents had the lowest invasion success, but abundances of resident species differed significantly from uninvaded controls indicating that the invader still influenced community dynamics. Experienced invaders in naïve communities did not uniformly outperform naïve invaders in comparable communities, supporting the emergence of increased biotic resistance as one consequence of evolution during invasions. Increased abundance and decreased temporal variation for one invader are consistent with evolution resulting in reduced attack rates on the invader in the novel community. Increased temporal variability in populations of resident species after biological invasions may predispose those populations to extinction, while decreased temporal variability in invader abundance could facilitate invader persistence. These effects on community dynamics may provide one mechanism to explain how evolution can exacerbate invasions in some communities and ameliorate invasions in others. Evolutionary history alone can affect temporal variation in the abundances of species, generating important consequences for interspecific interactions among species and complicating inferences about the consequences of temporal variability in biological communities.