A fungal endosymbiont of the grass Bromus setifolius: Distribution in some Andean populations, identification, and examination of beneficial properties

Endophyte infection levels were estimated in populations of the grass Bromus setifolius at several sites in the Andes Mountains in South America. The endophyte was identified as pertaining to the Neotyphodium tembladerae clade using sequence data. A high percentage of grass individuals infected by the endophyte was found in populations located in communities that contained leaf-cutting ants (Acromyrmex sp.). N. tembladerae was found to produce two mycotoxins (ergovaline and peramine) that are known to be toxic to insect herbivores. Feeding experiments demonstrated that fall armyworms preferred endophyte-free B. setifolius over endophyte-infected B. setifolius when given the option of both. The results of this investigation support the defensive mutualism hypothesis that defense of the host from herbivores is a basis for the mutualistic association between clavicipitaceous endosymbionts and host grasses.