Cultural Eutrophication Mediates Context-Dependent Eco-Evolutionary Feedbacks of a Fish Invader
Eco-evolutionary dynamics are typically depicted as direct reciprocal interactions between ongoing trait change and ecological change, but environmental context is increasingly recognized for its potential role in mediating evolution's effects on ecology and vice versa. Indeed, environmental context might be considered a third major player within any given eco-evolutionary dynamic, which may at times be determined by strong external drivers but also potentially dynamically remodeled by feedbacks from evolution's effects on ecology. In this study, we test for the environmental context effects of lake trophic state, a condition that is strongly shaped by both external and internal processes of aquatic systems. Specifically, we test whether and how oligotrophic or eutrophic conditions influence the community and ecosystem effects of recent phenotypic divergence of invasive White Perch (Morone americana) populations. Using a factorial treatment design, perch from oligotrophic and eutrophic lake sources were stocked into oligotrophic and eutrophic mesocosms to quantify their effects on pelagic and benthic communities as well as nutrient limitation and system productivity. Perch source influenced benthic invertebrates, primary production, and nutrient limitation, supporting the presence of a phenotype-to-ecology feedback. Importantly, effect size modeling revealed that these perch source effects varied with background trophic conditions and across pelagic versus benthic compartments, supporting context dependence. The specific context-dependent effects we observed suggest that remodeling of environmental context within eco-evolutionary dynamics might facilitate alternate stable state transitions initiated by cultural eutrophication.
The role of environmental context in mediating eco-evolutionary dynamics. Environmental context is depicted here as a ‘lens' or ‘filter' that modulates the degree to which any potential ecological response (ΔEi) is influenced by changes in a given trait or combination of traits (ΔXi), and vice versa. Environmental context effects on the evo-to-eco link include processes like ability of resource limitation and density conditions to environmentally modulate how much population abundance, community composition, or primary production change due to contemporary evolution of trophic specializations. Environmental context effects on the eco-to-evo link include ways in which the realized environment mediates the patterns and strength of selection, the heritabilities and genetic correlations of traits determining evolutionary responses to that selection, and the relative importance of phenotypic plasticity. Existing eco-evolutionary frameworks frequently ignore an explicit role of environmental context or implicitly treat it as fixed, but in theory it is likely to be dynamically remodeled by external drivers or internal feedbacks associated with emerging eco-evolutionary processes themselves.
Least squares means of gross primary production (GPP), ecosystem respiration (ER), and relative response ratio (+SE). Significance of each fish source (low productivity: LP; high productivity: HP) by community type (low productivity: LENV; high productivity: HENV) contrast against no fish treatments (NO) is shown by ** is P < 0.01, * is P < 0.05, and † is P < 0.10.
Effect sizes (Cohen's d) of fish additions relative to the NO fish controls for ecosystem and community metrics. Effect sizes are presented for each fish type (LP [dashed line and open circle] versus HP [solid line and closed circle]) and by background community type (low productivity [LENV] or high productivity [HENV]). Significance of each effect size is indicated (comparison of treatment to NO fish control) where ** is P < 0.01, * is P < 0.05, and † is P < 0.10. Horizontal line is NO baseline.
Overall effect size differences (absolute value of Cohen's d) between the two fish sources in alternate community (low productivity: LENV; high productivity: HENV) and habitat types (benthic or limnetic).
Contributor Notes
Associate Editor: D. M. Green.
From “Eco-Evolutionary Dynamics in Cold Blood,” an ASIH-sponsored symposium at the 2016 Joint Meeting of Ichthyologists and Herpetologists in New Orleans, Louisiana.