Research Interests

My research involves the study of aquatic ecosystems, and the development of mathematical frameworks to understand species interactions and their consequences to food web structure and dynamics. Animal species representing diverse taxa in disparate systems are confronted with and respond similarly to common ecosystem processes. By representing such processes with conceptual and mathematical frameworks, they are made explicit, are clarified, and comparison between systems that can yield additional insight is facilitated. I perform controlled experiments to validate model predictions, to help illustrate their connection with natural systems, and to expose unforeseen processes when experimental results do not match model predictions. As model experimental systems used in mesocosm work, I use a tadpole/larval dragonfly system and zooplankton communities from Michigan ponds.

A principal goal of my research program is to develop methodology to integrate what we learn from field observation and experimental studies with both theory, and models required to inform the management and stewardship of ecosystems.

Graduate Student Kevin Pangle taking a zooplankton net tow with Scott Peacor aboard the RV Shenehon

Current Research Projects

(Note: Abstracts to our papers are available on publications page)

Food web disruption by Bythotrephes in Lake Michigan: nonlethal effects of an invasive species

Collaborators: Kevin Pangle (Michigan State University)

The invasive predatory cladoceran Bythotrephes longimanus has been implicated as a serious threat to Great Lakes ecosystems by "disrupting" the food web, including negatively affecting fish recruitment. For example, there have been dramatic unexplained decreases in zooplankton densities in Lake Huron recently with associated effects on fish production- our work may help to explain these decreases. We are examining potential nonlethal effects of Bythotrephes in Lake Michigan, which arise primarily from induced vertical migration in prey to deeper, colder waters. The work combines field observations with laboratory and mesocosm studies (including studies of Bythotrephes predation rates as a function of light level and prey density, induced effects of Bythotrephes on prey vertical migration as a function of light level and prey density, competition of zooplankton prey, and other processes pertinent to observed field patterns). Our goal is to construct models that evaluate the indirect effects of Bythotrephes on fish, with a focus of the role of nonlethal effects.

Invasive predatory cladoceran Bythotrephes longimanus

This project is developing methods to evaluate predator nonlethal effects in natural field populations (which requires different methodology than in controlled venues), and to elucidate nonlethal effects in large, complex, aquatic systems. For example, we expect to couple physical processes (currents, mixing, temperature distribution) with predator-induced changes in prey spatial distribution in the next generation of forecasting models of fish recruitment used in management. In addition to experimental and field work, there is also a theoretical component of this research, in which the optimal behavior of Bythotrephes prey is modeled, and the ensuing population and community level effects examined.

A goal of this research is to improve how predator-prey relationships are represented in models, and therefore improve forecasting models of Great Lakes food web dynamics including alteration of fish production.

Daphnia

The origin of size variation in animal cohorts.

Collaborators:
Jim Bence (Michigan State University)
Earl Werner and Luis Schiesari (University of Michigan)
Cathy Pfister (University of Chicago)

Huge variation in size and growth rate is seen even in for sibling organisms born at the same time. And whereas (a) ecological and evolutionary biologists have long recognized that body size influences virtually every aspect of the relations between an organism and its internal and external environments, and (b) there is much evidence that variation in size can have large effects on ecological processes (such as e.g. stability), we know surprising little about the origin of size variation. We are using experimental studies, using tadpoles, to examine the size variation, and the effect of factors such as competition and predator presence on this variation. We are also examining this question theoretically, using individual based models and mathematics borrowed from statistics. This research has implications for how ecologists and fishery managers model populations and ecosystems.

Digital Organisms in a Virtual Ecosystem (DOVE): a tool to study food webs processes.

Collaborators:
Katrina Button, Eric Goodman, Bill Punch, Stefano Allesina (Michigan State University)
John Holland, Mercedes Pascual, Rick Riolo, Earl Werner, (University of Michigan)
Tim Hunter (Great Lakes Environmental Research Laboratory)

We are developing a computational system, called "DOVE" for "Digital Organisms in a Virtual Ecosystem" to address general food web problems, such as assembly rules, invasive species, and the effect of phenotypic plasticity on food web structure and dynamics. Our method draws on new computational techniques (e.g. individually based models, genetic algorithms and classifier systems sensu John Holland, Hidden Order 1995). We will build "virtual ecosystems" composed of populations of "digital organisms" to use as a tool to reveal and examine how species interactions scale up to affect community level patters. For example, in DOVE the digital organisms, like their real organism counterparts, face a tradeoff between acquiring resources and being preyed upon when they move to search for resources. Some species will likely solve this problem by conserving resources and avoiding risk, while others will move rapidly in order to attain high reproductive rates at the cost of high mortality due to predation. The basic premise is that if we can build artificial systems that capture features of natural systems not included in conventional theory, and we have unlimited knowledge and ability to manipulate and probe such artificial systems, then we can gain insight into, and discover processes affecting, food webs. It is our intention that some properties that are discovered using DOVE will be more examined in more detail with traditional modeling approaches. Initial results have revealed processes by which phenotypic plasticity affects species invasion and the stability of competitive interactions.
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Nonlethal predator effects on community level patterns.

Collaborators:
Earl Werner and Clay Cressler (University of Michigan)

When predators induce changes in prey traits, this can have large "nonlethal" effects on prey growth and survival, and indirectly on species the prey interacts with (trait-mediated indirect interactions). We are extending previous work that primarily examines the predator effect in simple (~ 3 species) systems on short (within generation) time scales, to community wide responses on long (multiple generation) time scales, using pond zooplankton communities. Experimental work is performed in mesocosms combined with laboratory studies to elucidate processes.

Theory of Harmful Algae Blooms (HABs) in the Great Lakes.

Collaborators:
Ace Sarnelle (Michigan State University)
Jingjie Zhang (Great Lakes Environmental Research Laboratory)

The central goal of this project is to enhance understanding of how nutrients and exotic herbivores ( Dreissena mussels) interact in promoting the abundance and relative dominance of harmful phytoplankton in the Great Lakes. In this project, we seek to understand the factors driving recent dramatic increases in the frequency and intensity of HABs in the Laurentian Great Lakes, and in particular the relationships between nutrient loading, HABs and food web dynamics, and the ecological bases for bloom formation. In collaboration with with investigators examining this problem experimentally, our goal is to develop theory to examine how invasive mussels affect HABs; We will use both "mechanistic" models based on recent theory that examines how tradeoffs affect competition, and more "realistic" structurally dynamic models. This is important, both to inform management policies (e.g. those that affect nutrient loading), and in order to develop predictive models that allow HABs forecast.

Scott Peacor, Assistant Professor
Department of Fisheries and Wildlife
Michigan State University
10D Natural Resources
East Lansing, MI 48824-1222
Phone: (517) 353-1910
Email:

Last updated: 2008-02-29