Graduate Thesis Or Dissertation

 

Systematics of the genus Torrubiella Público Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/br86b6306

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  • Torrubiella is a genus of entomopathogenic fungi in the Clavicipitaceae (Ascomycota). Species of the genus produce superficial perithecia on a loose mat of hyphae that forms directly on the host. The genus is estimated to contain about 70 species. Torrubiella is hypothesized to be a close relative of Cordyceps because of morphological similarities in perithecia, asci and ascospores. However, unlike Cordyceps, species of Torrubiella do not produce stipitate stromata. The two genera also differ in their host range. Torrubiella spp. attack spiders and scale insects, which are notably depauperate in the host profile of Cordyceps. Recent molecular studies rejected the monophyly of Cordyceps and resulted in the reclassification of Cordyceps (Cordyceps s. s., Elaphocordyceps, Metacordyceps and Ophiocordyceps) and the Clavcipitaceae s.l. into three families. Molecular analyses also did not support the monophyly of Torrubiella, but insufficient taxon sampling made conclusions about the genus difficult. To test and refine evolutionary hypotheses regarding the placement of Torrubiella in Clavicipitaceae and its relationship to Cordyceps, phylogenetic analyses of the Clavicipitaceae with an emphasis on Torrubiella were conducted. The phylogenetic informativeness of anamorph genera and host affiliation was also addressed. Weighted parsimony analyses were conducted on sequence data from five nuclear loci including: nuclear small subunit ribosomal DNA (nrSSU), nuclear large subunit ribosomal DNA (nrLSU), the largest (RPB1) and second largest (RPB2) subunits of RNA polymerase II, and translation elongation factor 1 a (tef). The monophyly of Torrubiella was rejected by these analyses, with species of the genus present in each of the three families of clavicipitaceous fungi and often intermixed among Cordyeps species. The morphological characters traditionally used to define the genus are therefore not phylogenetically informative. Two new genera are proposed to accommodate two lineages of torrubiellioid fungi. In addition, five species of Torrubiella are reclassified into different genera based on these phylogenetic analyses.
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