ABSTRACT
During the past two decades biologists have accumulated a substantial understanding of the pair-wise interactions between endophyte-infected grasses and their herbivores, the evolutionary origins of the endophytes, and the biochemistry and physiology of infection (Clay, 1996; White and Morgan-Jones, 1996; Saikkonen et al., 1998; Craven et al., 2001; Clay and Schardl, 2002). Despite this progress, the higher-level community and ecosystem consequences of grass-endophyte associations are not well resolved. Although fungal endophytes can have strong effects on their host plants, the importance of these plant symbionts in structuring pathogen and herbivore assemblages or guilds of predators and parasitoids is unclear. Endophyte infection of one dominant grass can alter the diversity and abundance of co-occurring plant species (Clay and Holah, 1999), but it is not known how widespread these effects are. Here, we explore how endophyte-grass symbioses might affect the structure and function of terrestrial communities, including mediation of both above-and belowground interactions. We also discuss the potential for endophytes to modify the properties of ecosystems, such as productivity and decomposition. Finally, we examine the role of variation among endophyte genotypes (particularly in chemical profiles) in mediating species interactions at the community level.
