Introduction

Ecologists interested in how traits mediating species interactions evolve have increasingly recognized that trait evolution is a consequence of multiple interacting species (Miller and Travis 1996; Strauss and Ambruster 1997; Thompson 1999; Strauss and Irwin 2004; Haloin and Strauss 2008). Species may alter the evolution of traits affecting multiple species through a number of direct or indirect pathways; examples include exerting conflicting selection pressures on the same traits (Siepielski and Benkman 2007a; Manzaneda et al. 2009) and predators indirectly altering the strength of species interactions (Werner and Peacor 2003). Although our understanding of the community context of species interactions has sharpened in the past decade (e.g., Strauss and Irwin 2004; Bascompte and Jordano 2007; Johnson and Stinchcombe 2007), particularly with regards to spatial dynamics (e.g., Thompson 2005; Urban et al. 2008), a number of outstanding questions remain. For example, to what extent do interactions evolve because of adaptive evolution of traits mediating other species interactions? Similarly, how does the loss of an interacting species (e.g., relaxed selection) affect the evolution of other interactions? Finally, when and to what extent is variation in community and ecosystem patterns and processes influenced by adaptive evolution of traits mediating species interactions? Answers to these questions have important implications for our understanding of major topics in evolutionary biology including the evolutionary outcome of selection in multispecies interactions, the geographic mosaic of coevolution and even patterns of adaptive radiation.