@ARTICLE{TreeBASE2Ref19547, author = {Russell J.S. Orr and Anke St?ken and Thomas Rundberget and Wenche Eikrem and Kjetill S Jakobsen}, title = {Improved phylogenetic resolution of toxic and non-toxic Alexandrium strains using a concatenated rDNA approach.}, year = {2011}, keywords = {Alexandrium; phylogeny; PSP; PST; saxitoxin; STX}, doi = {}, url = {http://}, pmid = {}, journal = {Harmful Algae}, volume = {}, number = {}, pages = {}, abstract = {Dinoflagellates of the genus Alexandrium are known producers of paralytic shellfish toxins. Species within the genus have similar phenotypes making morphological identification problematical. The use of Alexandrium rDNA sequence data is therefore increasing, resulting in the improved resolution of evolutionary relationships by phylogenetic inferences. However, the true branching pattern within Alexandrium remains unresolved, with minimal support shown for the main phylogentic branch. The aim of this study is to improve phylogenetic resolution via a concatenated rDNA approach with a broad sample of taxa, allowing inference of the evolutionary pattern between species and toxins. 27 Alexandrium strains from 10 species were tested with HPLC for PSP toxin presence and additionally sequenced for 18S, ITS1, 5.8S, ITS2 and 28S rDNA before being phylogenetically inferred together with all available orthologous sequences from NCBI. The resulting alignment is the largest to date for the genus, in terms of both inferred characters and taxa, thus allowing for the improved phylogenetic resolution of evolutionary patterns there in. No phylogenetic pattern between PSP producing and non-producing strains could be established, however the terminal tamarensis complex was shown to produce more PSP analogues than basal clades. Additionally, we distinguish a high number of polymorphic regions between the two copies of A. fundyense rDNA, thus allowing us to demonstrate the presence of chimeric sequences within Genbank, as well as a possible over estimation of diversification within the tamarensis complex and the misidentification of numerous A. tamarense strains. } }

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