UBC Theses and Dissertations
Taxonomic investigation of selected species of Staurastrum meyen and Staurodesmus teiling from lakes of the Lower Fraser Valley, British Columbia Contant, Hélêne
An investigation of selected taxa of Staurastrum and Staurodesmus (Desmidiaceae, Desmidiales, Chlorophyta) was undertaken to help clarify their taxonomy. The study was conducted on samples collected in the lower Fraser Valley (British Columbia). Sampling was done over a 2 1/2 year period in four main lakes (Jacobs, Munday, Lost and Como Lakes) with physico-chemical analyses (pH, temperature, irradiation, alkalinity, dissolved oxygen, calcium, nitrate, phosphate) used to characterize the habitats. Observations of field material revealed nine new records and 56 new distribution records of Staurastrum for British Columbia. One hundred and thirty-six clones comprising 18 taxa of Staurastrum and two taxa of Staurodesmus out of 310 clones of desmids successfully isolated in culture were studied. Morphological variation of the clonal isolates was studied with the light microscope and the scanning electron microscope (SEM). Cell dimensions and cell radiation were measured in each of the 136 clones studied and the length:width ratio (L/l), standard deviation and coefficient of variation were calculated for each. For the 199 taxa studied, more than 350 publications were consulted. These included original descriptions, records of distribution of taxa studied as well as infraspecific and related taxa. Comparison of variations observed in culture and field material were made with the literature and 33 synonyms were proposed. Growth and morphological studies in different environmental conditions (medium, irradiation, temperature, pH) were carried out with a triradiate clone of Staurastrum inflexum Brebisson (clone HC 18). Growth rate varied in the different environmental conditions tested but morphological variation was usually not affected. An analysis of variance showed no significant difference between cell size or cell radiation in different conditions, although higher pH (6.20 compared to 4.62) produced more tetraradiate cells. Attempts to induce sexual reproduction in different environmental conditions were unsuccessful. Control clones of St. gladiosum Turner and Cosmarium botrytis Meyen ex Ralfs from culture collections did show conjugation in similar conditions.
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