J Huisman Universiteit van Amsterdam
Thursday 30th October 2014 - 09:30 to 10:05
INI Seminar Room 1
Co-authors: Elisa Beninca (University of Amsterdam), Stephen Ellner (Cornell University) Many ecological studies have focused on equilibrium dynamics. Examples in microbial ecology are provided by chemostat studies in which species interactions are investigated until steady state is reached. In this presentation, I will take a different perspective by highlighting non-equilibrium dynamics in ecological communities. First, I will show that interaction networks consisting of multiple species can produce permanent changes in community structure, with chaotic ups and downs in species abundances such that the species composition never reaches an equilibrium state. This is illustrated by several controlled laboratory experiments with microbial food webs. Next, I will discuss possible underlying mechanisms that may generate such complex dynamics. For instance, predator and prey species can display classical predator-prey oscillations. Analysis of experimental data shows that the coupling of several predator-prey systems can cause intriguing species fluctuations, in which the community shifts back and forth between different predator-prey cycles in a chaotic fashion. Finally, I present field data of a cyclic succession sustained by rock-paper-scissors dynamics over many years. Analysis of the population dynamics reveals that the cyclic species replacement moves back and forth between stabilizing and chaotic dynamics. The results are supported by a simple community model, which shows that seasonal variation is likely the environmental driver that pushes this cyclic succession to the edge of chaos. Microbial communities typically consist of numerous species, involved in a multitude of species interactions. Hence, this non-equilibrium perspective may find application in a wide range of different fields. Examples include studies of natural communities in terrestrial, freshwater and marine ecosystems, but also the microbial gut flora, microbial disease dynamics, or the use of microbial communities in wastewater treatment and other biotechnological applications.