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1 The University of Alabama, Tuscaloosa, AL
2 Dept of Biological Sciences, The Univ of Alabama, Box 870344 / 319 Biology, Tuscaloosa, AL, 35487-0344
3 Dept of Biological Sciences, Univ of Alabama, 319 Biology, Box 870344, Tuscaloosa, AL, 35487, United States of America
4 Yetminster, 18 St.Osmund Close, Sherborne, Dorset, DT9 6LU, United Kingdom
5 University of Maine, Orono, Maine
6 N 181 Ln 482, Ta T'ung Rd Sec 2, Tainan, 702, Taiwan
The order Spizellomycetales was delineated based on a unique suite of zoospore ultrastructural characters and currently includes five genera and 14 validly published species, all of which have a propensity for soil habitats. We generated DNA sequences from small (SSU), large (LSU) and 5.8S ribosomal subunit genes to assess the monophyly of all genera and species in this order. The 53 cultures analyzed included isolates on which all described species were based, plus other spizellomycetalean cultures. Phylogenetic placement of these chytrids was explored using maximum parsimony and maximum likelihood analyses, both of which yielded comparable topologies. Kochiomyces, Powellomyces, and Triparticalcar were monophyletic, while Gaertneriomyces and Spizellomyces were polyphyletic. Isolates, distinct from described species, clustered among each of the five genera, indicating that species diversity in genera is greater than currently recognized. One isolate formed a clade that included no described species, representing a new genus. Zoospore ultrastructural features and architecture seem to be good indicators of phylogenetic relationships, but finer scrutiny of characters such as kinetosome-associated structures (KAS) is needed to understand more clearly the diversity within this order as it is revised.
Key words: chytrid, Gaertneriomyces, Kochiomyces, Powellomyces, Spizellomyces
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