Abstract
Clavicipitalean fungi have evolved to survive as saprophytes, degrading organic material, as well as biotrophs of plants, fungi, nematodes, and insects. They have become particularly successful as epibionts and endophytes of grasses. We believe that the associations between clavicipitalean fungi and their hosts constitute unique biotrophic symbioses where the stages of physiological adaptation to the plant host may be examined to gain an understanding of how evolution among these fungi has progressed.