Fungal endophytes: A continuum of interactions with host plants

Endophytic fungi living asymptomatically within plant tissues have been fou nd in virtually all plant species. Endophytes are considered plant mutualis ts: They receive nutrition and protection from the host plant while the hos t plant may benefit from enhanced competitive abilities and increased resis tance to herbivores, pathogens, and various abiotic stresses. Limited evide nce also indicates that endophytes may influence population dynamics, plant community diversity, and ecosystem function. However, most of the empirica l evidence for this mutualism and its ecological consequences has been base d on a few agronomic grass endophytes. More recent studies suggest that end ophyte-host plant interactions are variable and range from antagonistic to mutualistic. A more comprehensive view of the ecology and evolution of endo phytes and host plants is needed. This article discusses how life history t raits-such as fungal reproduction and pattern of infections and genotypic v ariation and ecological factors-influence the direction and strength of the endophyte-host plant interaction.