ABSTRACT
Determination of the processes that maintain biological diversity is one of the primary aims of community ecology (Morin 1999). Although early research focused on negative interactions (e.g., competition and predation) as the main biotic factors structuring plant communities and regulating biological diversity (e.g., Grime 1973; Connell 1978; Tilman 1982), more recent studies have started to examine the importance of positive interactions on community structure and biological diversity (Bruno, Stachowicz, and Bertness 2003; Michalet et al. 2006). Positive interactions are defined as nontrophic interspecific interactions that increase the average individual fitness of one species (Bertness and Callaway 1994; Callaway 1995; Bruno, Stachowicz, and Bertness 2003; Callaway 2007). Therefore, the presence of one plant species enhances the chances that another species co-occurs in the same place, indicating that positive interactions may determine biological diversity.
