Phylogenetic Advances in Leotiomycetes, an Understudied Clade of Taxonomically and Ecologically Diverse Fungi

The class Leotiomycetes encompasses many fungi that were historically classified as inoperculate discomycetes. Molecular phylogenetics has changed our perception of the diversity of higher taxonomic lineages and morphologies in the class as well as our understanding of how these clades are related to one another. Leotiomycetes are found in all environments where researchers have explored and have myriad ecological strategies – including economically important pathogens (e.g., powdery mildews on various plants and the causal agent of the white-nose syndrome of bats), endophytes, saprobes, and mycorrhizae. In this article, we provide a summary of the morphological and ecological diversity of Leotiomycetes, and an overview of the taxonomic diversity and systematics. Major challenges in studying this group include historical biases in sampling outside of temperate Europe and North America and a lack of sequence data for many taxa especially in the sprawling mega-order Helotiales. With the help of environmental sequencing and genomic-scale data, researchers are beginning to reveal new perspectives on Leotiomycetes ecology, evolution, and systematics.