'University of Pretoria - Department of Philosophy'
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.PhDMicrobiology and Plant PathologyUnrestricte
