Lac Hertel

Fussmann Lab
Department of Biology

Chemostats

Eco-evolutionary dynamics in chemostats

Brachionus calyciflorus with eggs The planktonic rotifer Brachionus calyciflorus

The theme

A central goal of our research is to better understand the relationship between the diversity and the dynamics of ecological communities. Many species of lake plankton (rotifers, water fleas) reproduce parthenogenetically so that multiple clonal lines of one species coexist during the growing season.

As a result, lake plankton communities are not only diverse at the species level but also within species (genetic diversity). Genetic diversity opens the door for rapid evolutionary changes through selection of genotypes.

 
Chemostats Chemostats containing experimental predator-prey cultures. Setup at the University of Potsdam.
The questions
  • How do ecological and evolutionary processes co-determine the dynamics in plankton communities?
  • How does genetic diversity of predator populations affect predator-prey dynamics?
  • How does stress (through high temperature or cyanotoxins) alter the dynamics of evolvable (multiple clones) vs. evolutionarily static (monoclonal) populations?
 
Satorius chemostats Sartorius chemostat in the Fussmann lab, funded by CFI.
The system

We tackle these questions by running controlled chemostat experiments in the laboratory. Chemostats are glass vessels that contain nutrients and aquatic microbial populations, in our case often food chains of phytoplankton and rotifers. Chemostats are bioreactors that are operated as flow-through systems, i.e. input and output can be controlled by the experimenter. Chemostats are uniquely suited to studying the population dynamics of model organisms. Another advantage is that the experimental system can easily be formulated as a dynamic mathematical model.

Our chemostat cultures contain simple food webs: phytoplankton species such as Chlorella, Scenedesmus, Monoraphidium and their predators, rotifer zooplankton such as Brachionus calyciflorus, B. havanaensis or Asplanchna priodonta.

We are in the process of developing DNA-based molecular techniques that allow us to track the genetic diversity of rotifers of the species Brachionus calyciflorus over the course of our experiments.

 

Nature cover Rapid prey evolution. Cover with green algae (Chlorella) and the rotifer Brachionus calyciflorus used in a study by Yoshida et al

What we know already

We have shown previously how rapid evolution of the prey can dramatically alter a classic ecological phenomenon, predator-prey cycling. We now turn to predator evolution, predator-prey co-evolution and evolutionary dynamics in more complex, food-web communities.

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The people
  • We collaborate closely with the Cornell Chemostat Group on this topic.
  • Postdoc Alison Derry runs chemostats with rotifers and cyanobacteria.
  • Grad student Caolan Kovach-Orr (with assistant Noah Dewar) has started theoretical and experimental work in the fall 2008.

 

Working group Fussmann lab at work ...
The funding