Phenotypic and community consequences of captive propagation in mosquitofish

Intraspecific variation in a predator changes intertidal community through effects on a foundation species

Intraspecific variation is an important form of biodiversity that can alter community and ecosystem properties. Recent work demonstrates the community effects of intraspecific variation in predators via altering prey communities and in foundation species via shaping habitat attributes. However, tests of the community effects of intraspecific trait variation in predators acting on foundation species are lacking despite the fact that consumption of foundation species can have strong community effects by shaping habitat structure. Here, we tested the hypothesis that intraspecific foraging differences among populations of mussel-drilling dogwhelk predators (Nucella) differentially alter intertidal communities through effects on foundational mussels. We conducted a 9-month field experiment where we exposed intertidal mussel bed communities to predation from three Nucella populations that exhibit differences in size-selectivity and consumption time for mussel prey. At the end of the experiment, we measured mussel bed structure, species diversity, and community composition. While exposure to Nucella originating from different populations did not significantly alter overall community diversity, we found that differences in Nucella mussel selectivity significantly altered foundational mussel bed structure, which in turn altered the biomass of shore crabs and periwinkle snails. Our study extends the emerging paradigm of the ecological importance of intraspecific variation to include the effects of intraspecific variation on predators of foundation species.

Inconsistent evolution and growth-survival tradeoffs in Gambusia affinis

Growth-survival tradeoffs may be a generalizable mechanism influencing trajectories of prey evolution. Here, we investigate evolutionary contributions to growth and survival in western mosquitofish (Gambusia affinis) from 10 populations from high- and low-predation ancestral environments. We assess (i) the degree to which evolutionary components of growth and survival are consistent or inconsistent across populations within ancestral predation environments, and (ii) whether growth and survival trade off at the population level. We measure growth and survival on groups of common-reared mosquitofish in pond mesocosms. We find that evolution of growth is consistent, with fish from low-predation ancestral environments showing higher growth, while the evolution of survival is inconsistent, with significant population-level divergence unrelated to ancestral predation environment. Such inconsistency prevents a growth-survival tradeoff across populations. Thus, the generalizability of contemporary evolution probably depends on local context of evolutionary tradeoffs, and a continued focus on singular selective agents (e.g. predators) without such local context will impede insights into generalizable evolutionary patterns.

The Importance of Eco-evolutionary Potential in the Anthropocene

Humans are dominant global drivers of ecological and evolutionary change, rearranging ecosystems and natural selection. In the present article, we show increasing evidence that human activity also plays a disproportionate role in shaping the eco-evolutionary potential of systems—the likelihood of ecological change generating evolutionary change and vice versa. We suggest that the net outcome of human influences on trait change, ecology, and the feedback loops that link them will often (but not always) be to increase eco-evolutionary potential, with important consequences for stability and resilience of populations, communities, and ecosystems. We also integrate existing ecological and evolutionary metrics to predict and manage the eco-evolutionary dynamics of human-affected systems. To support this framework, we use a simple eco–evo feedback model to show that factors affecting eco-evolutionary potential are major determinants of eco-evolutionary dynamics. Our framework suggests that proper management of anthropogenic effects requires a science of human effects on eco-evolutionary potential.

Prey adaptation along a competition-defense tradeoff cryptically shifts trophic cascades from density- to trait-mediated

Trophic cascades have become a dominant paradigm in ecology, yet considerable debate remains about the relative strength of density- (consumptive) and trait-mediated (non-consumptive) effects in trophic cascades. This debate may, in part, be resolved by considering prey experience, which shapes prey traits (through genetic and plastic change) and influences prey survival (and therefore density). Here, we investigate the cascading role of prey experience through the addition of mosquitofish (Gambusia affinis) from predator-experienced or predator-naïve sources to mesocosms containing piscivorous largemouth bass (Micropterus salmoides), zooplankton, and phytoplankton. These two sources were positioned along a competition-defense tradeoff. Results show that predator-naïve mosquitofish suffered higher depredation rates, which drove a density-mediated cascade, whereas predator-experienced mosquitofish exhibited higher survival but fed less, which drove a trait-mediated cascade. Both cascades were similar in strength, leading to indistinguishable top-down effects on lower trophic levels. Therefore, the accumulation of prey experience with predators can cryptically shift cascade mechanisms from density- to trait-mediated.

Eco-evolutionary feedbacks link prey adaptation to predator performance

Eco-evolutionary feedbacks may determine the outcome of predator-prey interactions in nature, but little work has been done to quantify the feedback effect of short-term prey adaptation on predator performance. We tested the effects of prey availability and recent (less than 100 years) prey adaptation on the feeding and growth rate of largemouth bass (Micropterus salmoides), foraging on western mosquitofish (Gambusia affinis). Field surveys showed higher densities and larger average body sizes of mosquitofish in recently introduced populations without bass. Over a six-week mesocosm experiment, bass were presented with either a high or low availability of mosquitofish prey from recently established populations either naive or experienced with bass. Naive mosquitofish were larger, less cryptic and more vulnerable to bass predation compared to their experienced counterparts. Bass consumed more naive prey, grew more quickly with naive prey, and grew more quickly per unit biomass of naive prey consumed. The effect of mosquitofish history with the bass on bass growth was similar in magnitude to the effect of mosquitofish availability. In showing that recently derived predation-related prey phenotypes strongly affect predator performance, this study supports the presence of reciprocal predator-prey trait feedbacks in nature.