Food Web Ecology & Evolution in a Changing World
JOIN THE LAB!
I'm currently accepting applications from graduate students interested in joining the lab, so go ahead and shoot me an email! :)
Contact: jean.gibert at duke.edu
I'm currently accepting applications from graduate students interested in joining the lab, so go ahead and shoot me an email! :)
Contact: jean.gibert at duke.edu
What we do
We study how traits, trait variation, spatial structure and eco-evolutionary dynamics influence predator-prey interactions, and through those, the structure and dynamics of food webs in a changing world. To do so, we combine mathematical models and computational tools with experimental approaches and data from public databases across systems and taxa.
As a general rule, our science occurs at the interface between a number of things: 1) spatial and temporal processes, 2) ecological and evolutionary dynamics, 3) individual, population and community-level processes, and, 4) theoretical, empirical and computational ecology.
Below are some papers representative of what we do and how we do it.
We study how traits, trait variation, spatial structure and eco-evolutionary dynamics influence predator-prey interactions, and through those, the structure and dynamics of food webs in a changing world. To do so, we combine mathematical models and computational tools with experimental approaches and data from public databases across systems and taxa.
As a general rule, our science occurs at the interface between a number of things: 1) spatial and temporal processes, 2) ecological and evolutionary dynamics, 3) individual, population and community-level processes, and, 4) theoretical, empirical and computational ecology.
Below are some papers representative of what we do and how we do it.
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1) Phenotypic variation explains food web structure (PNAS, 2017) Food webs (i.e. networks of species and their feeding interactions) share multiple structural features across ecosystems. The factors explaining such similarities are still debated, and the role played by most organismal traits and their intraspecific variation is unknown. We assessed how variation in traits controlling predator-prey interactions (e.g., body size) affects food web structure. We showed that larger phenotypic variation increases connectivity among predators and their prey as well as total food intake rate. For predators able to eat only a few species (i.e., specialists), low phenotypic variation maximizes intake rates, while the opposite is true for consumers with broader diets (i.e., generalists). We also showed that variation sets predator trophic level by determining interaction strengths with prey at different trophic levels. Merging these results, we made two general predictions about the structure of food webs: 1) trophic level should increase with predator connectivity, and 2) interaction strengths should decrease with prey trophic level. We confirmed these predictions empirically using a global dataset of well-resolved food webs. Our results provide new understanding of the processes structuring food webs that include functional traits and their naturally occurring variation. |
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2) Environmental conditions impact prey traits, which determine population growth and predator-prey interactions (Ecology Letters, 2017) Population dynamics and species persistence are often mediated by species traits. Yet many important traits, like body size, can be set by resource availability and predation risk. Environmentally induced changes in resource levels or predation risk may thus have downstream ecological consequences. Using a series of microcosm experiments, we assessed whether quantity and type of resources affect the phenotype, the population dynamics, and the susceptibility to predation of a mixotrophic protist through experiments and a model. We showed that cell shape, but not size, changes with resource levels and type, and is linked to carrying capacity, thus affecting population dynamics. Also, these changes led to differential susceptibility to predation, with direct consequences for predator-prey dynamics. We thus described important links between environmental changes, traits, population dynamics and ecological interactions, that underscore the need to further understand how trait-mediated interactions may respond to environmental shifts in resource levels in an increasingly changing world. |
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3) Eco-evolutionary dynamics determine food web structure (Frontiers in Ecology and Evolution, in revision) Organismal traits and their evolution can strongly influence food web structure and dynamics. To what extent the evolution of such traits impact food web structure, however, is poorly understood. We investigated a simple three-species omnivory food web module where the attack rates of all predators evolve as ecological dynamics unfold, such that predator trophic levels were themselves dynamic. We assumed a timescale where other vital rates that govern population dynamics are constant and incorporate a well-known tradeoff between attack rates and the conversion of prey biomass into predator biomass as a consequence of increased metabolic costs. We showed that this eco-evolutionary model yields a surprisingly rich array of dynamics. Moreover, even small amounts of selection led to important differences in the abundance, trophic and biomass structure of the food web. Systems in which intermediate predators are strongly constrained by tradeoffs led to hourglass-shaped food webs, where basal resources and top predators have large abundances, but intermediate predators are rare, like those observed in some marine ecosystems. Such food webs are also characterized by a relatively low maximum trophic level. Systems in which intermediate predators have low weaker tradeoffs, led to pyramid-shaped food webs, where basal resources are more abundant than intermediate and top predators, like those observed in some terrestrial system. Such food webs had a relatively larger maximum trophic level as well. Overall, our results suggested that eco-evolutionary dynamics can strongly influence the abundance-, trophic-, and biomass-structure of food webs, even in the presence of small levels of selection, thus stressing the importance of taking traits and trait evolution into account to further understand community-level patterns and processes. |
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4) Temperature determines animal movement, which impacts predator-prey interactions (Global Change Biology, 2016)
A pressing challenge in ecology is to understand the effects of changing global temperatures on food web structure and dynamics. The stability of these complex ecological networks largely depends on how predator-prey interactions may respond to temperature changes. Because predators and prey rely on their velocities to catch food or avoid being eaten, understanding how temperatures may affect animal movement is central to this quest. Despite our efforts, we still lack a mechanistic understanding of how the effect of temperature on metabolic processes scales up to animal movement and beyond. We merged a biomechanical approach, the Metabolic Theory of Ecology and empirical data to show that animal movement displays multiple regimes of temperature dependence. We also showed that crossing these regimes has important consequences for population dynamics and stability, and that these effects depend on the parameters controlling predator-prey interactions. We argued that this dependence upon interaction parameters may help explain why experimental work on the temperature dependence of interaction strengths has so far yielded conflicting results. More importantly, these changes in the temperature dependence of animal movement can have consequences that go well beyond ecological interactions and affect, for example, animal communication, mating, sensory detection, and any behavioral modality dependent on the movement of limbs. Finally, by not taking into account the changes in temperature dependence reported here we might not be able to properly forecast the impact of global warming on ecological processes and propose appropriate mitigation action when needed. |
