Theoretical Population Biology 74 (2008) 34–45 Contents lists available at ScienceDirect Theoretical Population Biology journal homepage: www.elsevier.com/locate/tpb Ecological consequences of evolution in plant defenses in a metacommunity N. Loeuille a,b,∗ , M.A. Leibold a a Section of Integrative Biology, University of Texas, Austin, TX 78712, USA b Laboratoire d’écologie, UMR7625, Université Paris VI, 75005 Paris, France article info Article history: Received 11 May 2007 Available online 29 April 2008 Keywords: Plant defenses Quantitative and qualitative defenses Metacommunity Food web structure Adaptation Evolution abstract Dispersal can affect the assembly of local communities in a metacommunity as well as evolution of local populations in a metapopulation. These two processes may also affect each other in ways that have not yet been well studied and that may have novel effects on community structure. Here, we illustrate the interaction of these two processes on community structure with a model of adaptive evolutionary dynamics of plant defenses in a metacommunity food web involving multiple patches along a productivity gradient. We find an enhanced suite of adaptive plant types in our metacommunity model than is predicted in the absence of dispersal. We also find that this, and the movement of nutrients among patches via dispersal, alters patterns of food web architecture, trophic structure and diversity along the productivity gradient. Overall, our model illustrates that evolutionary and metacommunity dynamics may influence communities in complex interactive ways that may not be predicted by models that ignore either of these types of processes. © 2008 Elsevier Inc. All rights reserved. 1. Introduction It is increasingly being recognized that ecological interactions in local communities can be strongly affected by spatial effects due to the influence of dispersal from other such local communities. One approach to understanding these effects is the concept of metacommunity which is defined as a set of local communities that are connected by dispersal (see Leibold et al. (2004) and Holyoak et al. (2005)). Metacommunity theory identifies at least two ways by which community dynamics are altered by dispersal: – altered community assembly where dispersal is important by providing colonists that can increase when rare and thus fuel the rate of composition change. – mass effects in which emigration from some sites supports higher population sizes at other sites than would exist in isolated local communities with possible consequences for the rest of the community. Current work on metacommunities is altering the inter- pretation of numerous ecological phenomena including trophic structure, patterns of biodiversity, compositional change along gradients, and food web structure (Leibold et al., 2004; Holyoak et al., 2005). Here, we evaluate if such phenomena may also depend on how adaptive evolution interacts with dispersal. Spatial effects related to gene flow and dispersal have also been understood to affect evolutionary dynamics for a long ∗ Corresponding author. E-mail address: nicolas.loeuille@normalesup.org (N. Loeuille). time (Wright, 1969), but the influence of such evolution on metacommunities has not yet been evaluated. The effects are most likely to be important when they affect adaptive evolution and there is a solid body of work that has examined the role of dispersal on adaptive traits, albeit while ignoring metacommunity ecology. It shows that dispersal can play two major roles that affect how local adaptation occurs. First, dispersal can provide genetic variants that may enhance the rate of evolution if they help maintain genetic variability on which selection can act and, second, they can inhibit adaptation when gene flow by individuals that are not adapted to local conditions is sufficiently strong to counteract local selection. Both of these effects can be important in affecting the common assumption in metacommunity ecology that species traits are fixed across local communities and both effects are roughly parallel in nature to those that affect metacommunity dynamics. Adaptive dynamics in spatially structured populations and community assembly in metacommunities may thus interact with each other such that community assembly affects adaptive evolution and coevolution (e.g. Thompson (2005)) and evolved differences in a given species affects community assembly (e.g. Whitham et al. (2003)). Recent observations that adaptive evolution and ecological dynamics in many local communities can occur on similar time scales (Hairston et al., 2005) makes the likelihood of such an interaction especially compelling. In this paper, we consider how evolutionary and metacommu- nity dynamics interact as a function of dispersal in a tractable food web ’module’. Our goal is to illustrate by example the potential in- teraction of these effects on both evolutionary and ecological pre- dictions. For illustrative purposes, we focus on the evolution of 0040-5809/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.tpb.2008.04.004