PARENT SESSION
Organized Oral Session 45: Evolution in metacommunities: A new framework for species coexistence
Organizer(s): MC Urban and MA Leibold
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 516 A, Level 5, Palais des congrès de Montréal
Evolution of plant defenses within metacommunities.
Loeuille, Nicolas*,1, Leibold, Mathew1, 1 Section of Integrative Biology, University of Texas at Austin, Austin, Texas, USA
ABSTRACT- We study the evolution of plante defenses in a metacommunity whose patches vary in terms of nutrient supply. Four species are present initially in the metacommunity: two species of plantes and two species of herbivores (one specialist and one generalist). Two types of plante defenses are considered. Qualitative defenses (such as toxins) efficiently reduce the consumption of the plante by the generalist herbivore while it has no effect or may even attract the specialist herbivore. Quantitative defenses (such as digestibility reducing compounds) are efficient against all types of herbivores, but are costly in terms of growth. We compare the evolution of these defenses in the different patches considered separately (local adaptation), and then in the metacommunity context. We pay a particular attention to the distribution the defense levels and to the structure of the community in the different patches. We also study the alpha (patch-level) and gamma (metacommunity-level) diversity of defensive strategies depending on the amount of dispersal in the metacommunity. Consistently with previous studies, we find that the amount of defenses is high in rich patches and low in poor patches, independently of the dispersal. As a consequence of the high level of defenses, the interaction between the plante and the generalist herbivore tends to be very small in rich patches. The community then consists of two independent food chains instead of the food web unit presents in the other patches. While gamma diversity decreases monotically with dispersal, the variation of the alpha diversity depends on the patch. In poor and intermediate patches, the relation between alpha diversity and dispersal is unimodal, while is richer patches, diversity is constant and low.
Key words: metacommunity, adaptive dynamics, anti herbivore defenses, alpha and gamma diversity