An analysis of ergot alkaloids in the Clavicipitaceae (Hypocreales, Ascomycota) and ecological implications

Fungi of family Clavicipitaceae (Hypocreales; Ascomycetes) were evaluated according to their ecological habits (free-living, insect parasite, epibiotic or endophytic) and trophic mode (saprotrophic/insect necrotroph; scale insect necrotroph/plant biotroph; or plant biotroph). In order to infer evolutionary relationships phylogenetic analysis on large subunit rDNA sequence data were used on taxa selected to represent a range of ecological habits and trophic modes in the family. The capacities of the fungi to produce ergot alkaloids (or ergoline structures) in culture were evaluated. In this study we found that production of ergot alkaloids was a feature of Clavicipitaceae that were biotrophs on plants. Ergoline alkaloid-producing plant biotrophs were distributed in two clades of the Clavicipitaceae that included plant biotrophic forms. This is the first study that links ergot alkaloid production in the Clavicipitaceae with plant biotrophy. To explain this linkage we offer the hypothesis that the abundance of nutrients in living plants may permit the plant biotrophic forms to produce ergot alkaloids for defensive purposes. The exposure of these fungi on the surfaces of plants increases their vulnerability to herbivory; production of ergot alkaloids reduces that vulnerability.