Scale Biogenesis in Synurophycean Protists: Phylogenetic Implications |
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Authors: | James L Wee Dr Robert A Andersen |
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Institution: | 1. Department of Biological Sciences , Loyola University , New Orleans, Louisiana, 70118, USA;2. Bigelow Laboratory for Ocean Sciences , P.O. Box 475, McKown Point, West Boothbay Harbor, Maine, 04575, USA |
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Abstract: | The Synurophyceae is a class of golden-brown, freshwater, photosynthetic flagellates with a world-wide distribution. A well-developed taxonomy exists where genera and species are distinguished by colony or cell morphology or by the siliceous scales that cover the cells. However, phylogenetic relationships within the class are poorly understood, and incongruous taxonomic concepts occur. This study reviews scale morphology from field-collected samples and controlled culturing experiments as well as from studies of scale biogenesis. The information is used to identify homologous silicification surfaces among taxa and to document the diversity of the resulting scale structures. Thirty-two character states are coded into 11 characters in a cladistic analysis of 13 pivotal taxa. Colonial species are emphasized. One most-parsimonious phylogenetic tree is found (HI = 0, CI = 1). Synura lapponica is shown to be most closely related to Tessellaria volvocina. S. sphagnicola emerges at the base of the tree. Mallomonas caudata and the S. petersenii clade emerge from within Sectio Synura. Chrysodidymus synuroideus appears as an ancestral taxon in the Synura spinosa-like clade (i.e., Series Spinosae). The poorly understood developmental bases for some characters, especially secondary scale structures, are identified and may help focus future research. |
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Keywords: | heterokont algae cladistic analysis scale development scale morphology Synura Mallomonas Tessellaria Chrysodidymus |
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