Traditional taxonomy and analysis of the 18S rDNA, ITS2 and rbcL sequences of species of the freshwater microalgae family Selenastraceae

Abstract

This project proposes the use of traditional methods of taxonomy and analysis of sequences of the 18S rDNA, ITS2 and rbcL of species of freshwater microalgae family Selenastraceae. The main objective is to provide a basis for taxonomic identification of these organisms, whose biodiversity is currently scattered in "complex" Ankistrodesmaceae / Selenastraceae / Chlorellaceae / Oocystaceae, a taxonomically problematic group. For species level resolution, obtaining DNA barcode is a powerful tool, but it does not obviate the practices of traditional taxonomy: morphology, chemotaxonomy, and other collateral information (Hajibabaei et al. 2007). Organisms must be preliminarily entered into a reliable taxonomic system even if, in some groups, it may not be enough to differentiate the species without errors (as is the case of microalgae with their high morphological convergence rates, high incidence of polymorphism and cryptic species). In these cases, the DNA barcode associated with traditional methods of the taxonomy may be the definitive factor in the proper identification of the species. A relatively sound taxonomic base, based on morphological characters, 18S rDNA phylogenetic analysis and specific biochemical profiles is a great starting point for the provision of "vouchers" for obtaining DNA barcodes, but stil need complementary information. In coccoid green algae, the morphological features, although subjective, are extremely useful and necessary as a starting point, and in many cases might be determinants for differentiation (Fawley et al. 2005). However, morphological differences between the species are often only detectable through the cultures, and therefore the species employed in this study will be grown and sampled at various growth stages . (AU)