Patterns in mussel beds may reflect interaction between individual behavior and emergent environmental patternsPosted 09 Sep 2011 / 0
Mussel beds off of Polzeath, United Kingdom (photo by Andy F)
Natural selection is often oversimplified as the effect of the outside environment on the survival and reproduction probability of individual organisms. In the end this perspective has some value: individual organisms either survive and reproduce or they do not. But along the way, an important feedback occurs: the behaviors of individual organisms scale up to produce emergent changes in the environment, which means that in small or sometimes even dramatic ways individual organisms alter the selective regime they face.
A research report in the June 24th edition of Science entitled “Lévy Walks Evolve Through Interaction Between Movement and Environmental Complexity” elegantly reveals how this interplay between individual behavior and emergent social patterns influences the manner in which natural selection shapes behavior. The researchers involved (Monique de Jager,Franz J. Weissing, Peter M. J. Herman, Bart A. Nolet, and Johan van de Koppel) show that mussel beds are formed by opposing forces, as spatial aggregation allows mussels to cooperate to reduce risk from waves and predators but also increases competition for the algae they filter out of the water for food. Using a very elegant combination of mesocosm tank experiments with real mussels and an individual-based model assessing the the optimal behavior of virtual mussels, the researchers show that optimal movement is shaped not only by what provides immediate benefits but also by the effect that particular movement strategies have on emergent social patterning.
This is a really amazing study for two reasons. First, it is a great example of how individual-based models and real-system experiments can be used in concert to fully understand observed natural patterns. Second, it emphasizes that the phenomenon of emergence makes the long-suffering controversy over whether organisms are subject to individual selection alone seem silly: selection results from the interaction between individual and social optima.
In addition to the research article, Science also features a short summary of the importance of the work called “Why Did You Lévy?“.Behavioral Ecology, Competition, Cooperation, Emergence, Individual-based Models, Intertidal Zones, Population Growth, Spatially Explicit Modeling