title: Ribosomal DNA sequence variation among sympatric strains of the Cyclotella meneghiniana complex (Bacillariophyceae) reveals cryptic diversity.
abstract: Cyclotella meneghiniana Kützing is one of the most commonly found and intensively studied freshwater diatom species. However, it is considered taxonomically problematic because of its unusually wide ecological range and large frustule ultrastructural variation. As part of a study of morphological and genetic variation in this morphospecies, we surveyed nucleotide variation in the hypervariable D1/D2 regions of the 28S rDNA, in the ribosomal internal transcribed spacer region (containing ITS1, the 5.8S rDNA and ITS2) and in the 18S rDNA in a collection of 20 sympatric strains. High genetic variability and strong indications of genetic structure among the Cyclotella meneghiniana strains were found. Representatives of four genetically distinct--apparently reproductively isolated--groups were revealed among them. The random distribution of ITS variation within these four groups indicated that the genetic structure in Cyclotella meneghiniana can probably be explained by the presence of cryptic sexual species rather than by the lack of allogamous sexual reproduction. The morphological features traditionally used for species identification in this group cannot distinguish these putative cryptic species.
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany. bbeszteri@awi-bremerhaven.de
authors.forename: Bánk
authors.initials: B
authors.lastname: Beszteri
authors.forename: Eva
authors.initials: E
authors.lastname: Acs
authors.forename: Linda K
authors.initials: LK
authors.lastname: Medlin
mesh_terms: D000818:Animals; D044822:Biodiversity; D021903:DNA, Ribosomal Spacer / Q000235:genetics / Q000302:isolation & purification; D017377:Diatoms / Q000145:classification* / Q000235:genetics*; D014644:Genetic Variation; D005858:Germany; D008969:Molecular Sequence Data; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics / Q000302:isolation & purification; D012339:RNA, Ribosomal, 28S / Q000235:genetics / Q000302:isolation & purification; D011995:Recombination, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D021903:DNA, Ribosomal Spacer; D012337:RNA, Ribosomal, 18S; D012339:RNA, Ribosomal, 28S