Food Web Interactions in Community Assembly

The types of species that live in a given locality is a function of the environmental conditions present in that habitat, the spatial context within which that locality is embedded, and the history in which species arrive at a given community.  I have surveyed many wetland communities in order to observe patterns of local and regional species diversity of aquatic invertebrates and plants.  Using these data, we showed that the seeming paradox between patterns of species diversity and different spatial scales could be solved by considering the different spatial scales simultaneously (Chase and Leibold 2002).  We found that at local spatial scales, diversity first increased, and then declined with productivity, whereas at regional spatial scales, diversity increased monotonically with increasing productivity.  This result follows rather simply from the fact that with increasing productivity, the divergence in community structure from site-to-site (beta-diversity) increased.  I have also used similar analyses to show that patterns of disturbance (wetland drying) and dispersal rate (distance among wetlands) have different effects on species diversity and local and regional spatial scales (Chase 2003). 

From these patterns, colleagues and I have developed a series of theoretical models that predict when history should play a role in community organization, and create disparity in community composition among similar localities, and when it should not.  In 1000 liter cattle tanks, I have established communities of plants and animals that are otherwise identical in environmental conditions, but vary in the timing in which species entered.  In previous work, I have found that these communities can reside in alternative stable equilibria and have maintained themselves for over 5 years.  More recently, I have established a cattle tank experiment at Washington University’s Tyson Research Center to explicit test a variety of hypotheses abut the relative effects of environment, region, and history.  This project is funded by the National Science Foundation.

Overall View

Individual Tank

Another Individual Tank