The diversity of Scenedesmus and Desmodesmus (Chlorophyceae) in Itasca State Park, Minnesota, USA

Abstract Species of Scenedesmus and Desmodesmus are ubiquitous in freshwater ecosystems. However, phenotypic plasticity coupled with the minute variations between named species make the identification of taxa by light microscopy extremely difficult, especially from field samples. As a result, the actual level of diversity and distributions of these genera are not known. In this study, the diversity of Scenedesmus and Desmodesmus from Itasca State Park (ISP), Minnesota, USA was studied using culture techniques followed by light microscopy and internal transcribed spacer (ITS-2) rDNA sequence analysis. From 100 characterized isolates of Scenedesmus, Desmodesmus and allied isolates, 34 different sequence types were detected, 24 of which are different enough from each other to correspond to distinct taxa. This diversity greatly exceeds that described for these genera in previous studies of ISP algae using light microscopy alone. The sequences of five ISP isolates identically matched those of previously descri...

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