Fragilaria radians (Kützing) D.M.Williams et Round, the correct name for F. gracilis (Fragilariaceae, Bacillariophyta): a critical analysis of this species complex in Europe

Fragilaria gracilis is one of the most reported Fragilaria species in Europe, observed in a broad range of water bodies, ranging from (ultra)oligotrophic rivers to even eutrophic lakes. A revision of this im-portant taxon based on the analysis of the morphology of a large number of historic and recent populations was highly needed. In the present study, type material of Fragilaria gracilis and several related taxa such as Synedra radians, Fragilaria pseudolaevissima, S. utermoehlii, F. aquaplus, F. boreomongolica and F. tridentina together with more than 10 modern populations were investigated using LM and SEM observations. The results based on these comparisons show that Fragilaria (Synedra) radians is the name for the taxon formerly known as F. gracilis. Moreover, detailed analysis demonstrated that F. pseudolaevissima and Synedra utermoehlii are conspecific with F. radians and should be considered as heterotypic synonyms. The observations made in this study also resulted in the description of several new species, often with distinct ecologies and distribution ar-eas: Fragilaria huerlimannii Van de Vijver sp. nov., F. acerosa Van de Vijver, C.E.Wetzel, Jarlman et Ector sp. nov., F. neglecta Van de Vijver, C.E.Wetzel, Jarlman et Ector sp. nov., F. heudreana Van de Vijver, C.E.Wetzel et Ector sp. nov., F. eutraphenta Van de Vijver, Kusber et D.M.Williams sp. nov., and F. mertensiana Van de Vijver, C.E.Wetzel et Ector sp. nov. Using an analysis of the associated diatom flora, the ecological preferences of each taxon are briefly discussed

Validation of five diatom novelties published in “Freshwater Benthic Diatoms of Central Europe” and taxonomic treatment of the neglected species Tryblionella hantzschiana

In July 2017, Lange-Bertalot et al. (2017) published a revised and translated version of Hofmann et al. (2013)’s book on freshwater benthic diatoms of Central Europe. The revised edition includes a few nomenclatural novelties which neither conform to the Melbourne Code (McNeill et al. 2012) nor to the upcoming Shenzhen Code (see Turland et al. 2017). The treatment of Tryblionella gracilis W.Sm. and T. hantzschiana Grunow shows how nomenclatural and taxonomic data can sometimes be confusing. This paper validates five names invalidly published in Lange-Bertalot et al. (2017) whilst the valid but previously neglected name T. hantzschiana is proposed to replace Tryblionella tryblio Cantonati et Lange-Bert., nom. inval. The registration numbers refer to PhycoBank (Kusber et al. 2017) a registration system on algae (Barkworth et al. 2016) which recently went online