Food Webs

 

We also study the structure and dynamics of ecological networks describing 'who eats whom', at ecological and evolutionary time scales

In collaboration with Korinna Allhoff, we are developing food-web models that integrate evolutionary and ecological dynamics. The models start with a small food web exhibiting the simplest ecological processes: birth, death, and consumption rates. Within these ecological dynamics, we simulate speciation by allowing the offspring of existent species to randomly change/mutate some specific characteristics, which converts them in new species. These new species will survive or go extinct depending on the ecological context that they are subjected to, that is, their predators, competitors and/or resources. Using this type of modelling, we are evaluating: 1) the interplay between invasions and local mutations shaping community assembly and 2) the ecological/evolutionary conditions in which becoming a specialist or generalist is favored.

Effects of
ontogenetic diet
shifts on Food Webs
 
Body size determines key ecological and evolutionary processes of organisms. Therefore, organisms undergo extensive shifts in resources, competitors and predators as they grow in body size. In collaboration with Anna Kuparinen, we are developing theory on how ontogenetic diet shifts and rapid evolution of other life history traits affect food-web structure and dynamics
Impacts of fisheries on food-webs

Vast scientific research has demonstrated that overfishing causes species extinctions, decreases the abundance and body size of targeted populations and accelerates their maturation. However, we still lack good understanding and predictive power on how these impacts propagate through the trophic network, affect other species and alter the structure and dynamics of the whole community.

We help to develop such understanding by computationally evaluating effects of fisheries on complex communities using concepts and tools of complex networks.
Effects of artisanal fisheries on Chilean intertidal and subtidal food-webs
 
This project consist of evaluating the effects of artisanal fisheries on the structure and dynamics of complex food webs of the intertidal and subtidal ecosystems of Central Chile. To study those effects, we compiled data on trophic interactions and commercial loads to build the food webs and then simulate their community dynamics including human exploitation using “Allometric Trophic Network” models.
Finally, we are also developing theory that incorporates economic dynamics of fisheries into complex food web models. Stay tuned!
Fishing-induced life-history
changes degrade and destabilize
harvested ecosystems
Kuparinen et al. 2016, Scientific Reports
 
Fishing is widely known to magnify fluctuations in targeted populations. These fluctuations are
correlated with population shifts towards young, small, and more quickly maturing individuals.
However, the existence and nature of the mechanistic basis for these correlations and their potential ecosystem impacts remain highly uncertain. 
Here, we elucidate this basis and associated impacts by showing how fishing can increase fluctuations in fishes and their ecosystem, particularly when coupled with decreasing body sizes and advancing maturation characteristic of the life-history changes induced by fishing. More specifically, using an empirically parameterized network model of a well-studied lake ecosystem, we show how fishing may both increase fluctuations in fish abundances and also, when accompanied by decreasing body size of adults, further decrease fish abundance and increase temporal variability of fishes’ food resources and their ecosystem. In contrast, advanced maturation has relatively little effect except to increase variability in juvenile populations. Our findings illustrate how different mechanisms underlying life-history changes that may arise as evolutionary responses to intensive, size selective fishing can rapidly and continuously destabilize and degrade ecosystems even after fishing has ceased. This research helps better predict how life-history changes may reduce fishes’ resilience to fishing and ecosystems’ resistance to environmental variations.
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Dept. Ecology & Evolutionary Biology (EEB)

Ann Arbor, Michigan

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fsvaldov@umich.edu