The type of Nitzschia intermedia , an often-misidentified diatom in Europe with the description of a new Nitzschia species (Bacillariaceae, Bacillariophyceae)

Nitzschia intermedia is often misidentified due to a lack of good knowledge of its type population and the former grouping of species as synonyms in the early 1970s. The present contribution analyses and illustrates the type material of N. intermedia from Dresden and compares the observed results with published images of all presumed synonyms. In addition, a recently collected population from Flanders (Belgium), identified as N. intermedia, is also studied using light and scanning electron microscopy. Comparison with the type of N. intermedia showed that the Flemish should be separated from the type population and be described as a new species, N. intermediafalsa, based on differences in stria density, valve outline, areola structure on the keel and fibula density. For both species, the accompanying diatom flora is used to determine their ecological preferences.