Taxonomy and phylogeny of Ophiostoma spp. with Sporothrix anamorphs and their generic relationships in the Ophiostomatales

Abstract

The ophiostomatoid fungi included more than 450 species of ascomycetes specifically adapted for insect dispersal. Many of these species have a significant economic impact as sapstaining fungi or tree pathogens harmful to forestry industries, but some are also as opportunistic human pathogens. DNA based studies in recent years have shown that the majority of these fungi belonged in either the Ophiostomatales or Microascales (Sordariomycetes), with a few Sporothrix spp. grouping in the Microstromatales (Ustilaginomycetes). However, most phylogenetic studies have focussed on restricted numbers of taxa sharing similar morphology. The aim of the studies in this thesis was to reconsider the taxonomy of all the ophiostomatoid fungi at the order and family levels, and the status of genera and species with sporothrix-like anamorphs in the Ophiostomatales and Microstromatales. All available published sequence data were screened for reliable sequences representing as many species as possible, and new data were generated where necessary for ex-type or other isolates. The resulting phylogenies enabled the formal redefinition of the Ophiostomatales and Ophiostomataceae, and the description of two new families, the Graphiaceae (Microascales) and Quambalariaceae (Microstromatales). Problems relating to the delineation of Ophiostoma s.l., Leptographium s.l., and Raffaelea s.l. were exposed and discussed, 18 species complexes were defined in the Ophiostomatales, and four genera were formally redefined: Sporothrix, Graphium, Graphilbum and Knoxdaviesia. Forty six new combinations were made, primarily in Sporothrix, Ophiostoma, Graphilbum and Knoxdaviesia. One nomen novum was erected in Ceratocystis and one new Quambalaria species was described. A comprehensive nomenclator for 596 ophiostomatoid species including references to all descriptions, synonymies and phylogenetic data was also compiled. This study represents the first comprehensive, all-inclusive assessment of the taxonomy and nomenclature of the ophisotomatoid fungi based on phylogenetic relationships and the one fungus one name principles. Finally, the immediate and indiscriminate application of the one fungus one name principles in Ophiostoma s.l. and Leptographium s.l. might result in many unnecessary name changes. Thus, several recommendations have been made to ensure nomenclatural stability in these genera in the immediate future and until more robust phylogenies become available that can refine the delineation of these genera.