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A phylogenetic systematics study of the red algal family Dumontiaceae

University of British Columbia

A cladistic analysis of the red algal family Dumontiaceae supports the hypothesis that the ancestor of the family was multiaxial, with narrow poorly differentiated axial filaments, small pit connections, narrow rhizoidal filaments, and irregularly branched assimilatory filaments of cylindrical, uninucleate cells. Secondary pit connections and a cuticle were probably lacking. The terete or slightly flattened, subtidal, ephemeral gametophyte may have alternated with a crustose tetrasporophyte with small, lateral, basally attached cruciate tetrasporangia. The long, straight carpogonial branches of slightly differentiated cells terminated in a carpogonium with a long, straight trichogyne. Spermatangia occurred in double whorls around spermatangial mother cells. Following fertilization, the carpogonium divided transversely, and the connecting filaments that developed after fusion to cells of the carpogonial branch were proximally septate but distally nonseptate. The auxiliary cell occurred proximally on a filament slightly differentiated from assimilatory filaments. The connecting filament divided adjacent to an auxiliary cell, and the distal segment continued on to contact other auxiliary cells. The proximal segment, after fusing with the auxiliary cell, cut off 2-5 gonimoblast initials that produced a compact cystocarp of many, small carposporangia. Enlargement of pit connections in the auxiliary cell branch did not exceed 5 µm, and fusions between cells of the auxiliary cell branch or between cells of the gonimoblast were lacking. Spores germinated in a diprotocellular pattern. The hypothesized ancestral condition in the Dumontiaceae supports the origin of the family from a species in the Helminthocladiaceae sensu lato. No evidence was found that any member of the Dumontiaceae is either a direct ancestor or descendant of any other families of the Cryptonemiales or Gigartinales with the possible exception of the Peyssonneliaceae, Polyidaceae, and Rhizophyllidaceae. As a result of the cladistic analysis, the tribes Farlowieae and Dumontieae are recognized as distinct lineages in the Dumontiaceae, and the genera Dudresnaya and Neodilsea are recognized to be paraphyletic. In addition, the following taxonomic changes were made: The genera Acrosymphyton and Neoabbottiella were removed from the Dumontiaceae. Farlowia irregularis was recognized to represent a distinct genus. Neodilsea inteqra was reinstated in Dilsea, and N. integra var. lonqissima was raised to specific rank. The discovery of older specific epithets for Neodilsea americana and Weeksia fryeana necessitated new species combinations for these taxa. A new genus and species was described from Alaska. The genus Thuretellopsis was synonymized with Dudresnaya and the following synonymies were suggested: Thuretellopsis japonica with Dudresnaya minima, Farlowia compressa with F. mollis, Pikea robusta with P. californica, Weeksia digitata with W. reticulata and possibly both of these species with the species formerly known as Weeksia fryeana.

Text

2010-06-17

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http://hdl.handle.net/2429/25834

Botany

University of British Columbia

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