Four new species of Nitzschia sect. Tryblionella (Bacillariophyceae) resembling N. parvula

In the course of research on the diatoms from surface sediments sampled in the marine littoral and sublittoral worldwide, and in some freshwater localities in central Europe, several problematic taxa were encountered resembling Nitzschia parvula. We therefore undertook a light and scanning electron microscopical study of five species of Nitzschia belonging to the section Tryblionella. After a period of misidentification, one of the taxa studied, N. parvula, is now known from the type preparation. The remaining taxa are either new to science or have previously lacked formal descriptions. The first of them is found in freshwater habitats and is described here as N. beyeri Lange-Bertalot, whereas the second, from the tropical marine littoral, is described as N. schweikertii Witkowski, Lange-Bertalot, Ruppel & Kociolek. The third species is known in the literature by the manuscript name ‘Nitzschia subconstricta Grunow’. However, this name was not validly published and subconstricta has recently been used for another species, described by Desikachary & Prema (1987). Grunow's species is validly described here as N. ligowskii Witkowski, Lange-Bertalot, Kociolek & Brzezinska. It inhabits the marine littoral and is characterized by a very wide geographical distribution. The fourth new taxon, described here as N. buschbeckii Witkowski, Lange-Bertalot & Ruppel is known so far only from the Antarctic.