Mark Jewell

Student Speaker | Étudiant.e
Community dynamics are governed by two processes: species sorting and neutral drift. Much ink has been spilled in attempting to demonstrate that one of these processes is much more important than the other. The controversy is largely pointless, because both processes will be active at all times everywhere, and the main goal of community ecology should be to understand how the balance between them depends on the underlying physical and biotic characteristics of sites. The aim of the ABCD experiment is to estimate the contribution of species sorting and neutral drift to the dynamics of experimental communities of floating macrophytes. Species sorting and neutral drift will have directly opposed effects on the species composition of communities. Under species sorting, communities that initially differ in composition will converge on the same composition, which represents the stable equilibrium community for the conditions prevailing at a given kind of site. Under neutral drift, communities that are initially identical in composition will diverge over time. We report the results of this large-scale mesocosm experiment at McGill’s Large Array of Experimental Ponds (LEAP) installation at the Gault Nature Reserve. By manipulating initial relative abundances of species in highly replicated semi-natural aquatic communities and following community dynamics (changes over time in species composition), we can estimate the relative contributions of the opposing processes responsible for shaping communities.