Four new Navicula (Bacillariophyta) species from Swedish rivers

During an extensive survey of the diatoms of Swedish rivers, four new Navicula species (Bacillariophyceae) were found: Navicula antonioides sp. nov., N. ireneae sp. nov., N. scaniae sp. nov. and N. ceciliae sp. nov. The new species are described formally using light and scanning electron microscopy. All four species possess a unique set of morphological characters including the structure of the central raphe endings, the striation pattern, the valve dimensions and outline, which make it possible to separate them from similar Navicula taxa such as N. cryptocephala, N. radiosafallax or N. antonii. The ecological preferences of each species are briefly discussed. Finally, the distribution of Navicula s.s. taxa in European inland waters is briefly discussed.