This reference analyzes the ecology, evolution, genetics, physiology, and taxonomy of this diverse group of fungi for identification of common biological, biochemical, and genetic features and discovery of potential medical and agricultural applications. It traces and reconstruct the evolution of various host-endoparasite systems and studies recent taxonomic research and DNA sequence analyses on plant-infecting clavicipitaleans. Providing a holistic view of the entire clavicipitalean family, the book compares morphologic, geographic, and host variations among various clavicipitalean populations and examines key discoveries and compounds obtained in clavicipitalean studies.