REVSYS: Phylogenetics and Taxonomic Revision of the Rhizophydium Clade (Chytridiomycota)

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Chytrids are microscopic fungi with flagellated (motile) life stages ("zoosporic fungi") that are nearly ubiquitous in nature, yet are poorly known and often unrecognized. Some of the most important chytrid fungi are members of the Rhizophydium clade or lineage, including the deadly amphibian parasite Batrachochytrium dendrobatidis, numerous algal parasites, and soil-inhabiting degraders of refractory materials such as pollen grains, cellulose, chitin, and keratin. The current taxonomic classification, published in 1960, is out of date and is based primarily on obscure morphological features that exhibit plasticity, making it difficult to identify genera and species. Modern biological techniques in gene sequencing and electron microscopy provide an opportunity to re-evaluate these organisms using phylogenetically informative characters, both morphological and molecular. Recent analyses of nuclear ribosomal DNA sequences have helped define membership and revealed unexpected genetic diversity within the Rhizophydium clade, indicating that the biodiversity of this group has been under-appreciated. Drs. Martha Powell and Peter Letcher at the University of Alabama propose to use molecular and zoospore ultrastructural (cell-anatomical) characters to revise the taxonomy of this group. They will expand the geographic areas and habitats sampled to include temperate and tropical rainforests in both hemispheres, the number of genes analyzed, and the details of ultrastructural characters of zoospores. Their goals are to make identification of chytrids easier, document their occurrence in nature by geographic region and habitat, provide laboratory cultures authenticating classical species names, and train a graduate student who is an underrepresented minority student, and work with other collaborators in chytrid systematics and taxonomy. The outcome of the project will be a modern systematic synthesis of the Rhizophydium clade. The work will be the first monographic synthesis of a large group of chytrids based on both molecular and ultrastructural characters. Through collaboration with scientists in Australia, Argentina, and Costa Rica, the investigators will reveal chytrid diversity in tropical and temperate forests, habitats that are rapidly being degraded by deforestation and other anthropogenic activities. Tools that make chytrid systematics more accessible will be added to an existing web site with digital images, a database of chytrid laboratory cultures, and interactive identification keys. Molecular sequences added to GenBank will be valuable for studies exploring the functional role of chytrids in nature. Working in concert with the Center for Communication and Educational Technology, the graduate student trainee will learn about video production, interactive web education, and appropriate content for students at different levels. Newly produced materials will introduce numerous middle-school students in the Alabama system to fungal biology and chytrid diversity through print and digital formats. Once introduced to chytrids, most students, teachers, and laypersons find these organisms fascinating.