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Zoospore ultrastructure and molecular phylogenetic analyses are revealing unrealized diversity among zoosporic fungi. The taxonomically challenging morphogenus Rhizophydium Schenk, with more than 220 described taxa, is now conceptually an order (Rhizophydiales Letcher) containing 10 families, 15 genera, and numerous undescribed isolates. Each family is a monophyletic group within which a unique suite of ultrastructural character states is found in the zoospore. Until now, the family Alphamycetaceae Letcher contained a single genus, Alphamyces Letcher. Herein we analyze zoospore ultrastructure and LSU and ITS1-5.8S-ITS2 rRNA gene sequences of 11 isolates in Alphamycetaceae from Australia and North, Central, and South America, and delineate two new genera, Betamyces and Gammamyces, each with a distinct zoospore subtype within the family. This work provides a blueprint for additional taxonomic revisions in Rhizophydiales, and the results indicate that sampling from diverse habitats and localities is necessary to reveal diversity among chytrids in Rhizophydiales. |
