Morphological and molecular phylogenetic studies on Fistulifera saprophila

Abstract

Accurate taxonomic identification provides the foundation for a number of diatom applications, such as the ecological monitoring of waters and the reconstruction of past environments. Despite significant recent developments in diatom taxonomy and phylogenetics, to date, only a few taxa have been studied extensively using a wide range of techniques. In this paper, data gained from intensive research on the morphology of live and cleaned diatom cells of two Fistulifera saprophila (Lange-Bertalot & Bonik) Lange-Bertalot strains isolated from the Gulf of Gdańsk are discussed. This study suggests that because specimens of F. saprophila have very delicate frustules prone to dissolution, the species has not been fully investigated and, therefore, a revised description is presented. Data on live cells and colony morphology, as well as interesting findings on the discrepancies between measurements of wet-mounted, dried and Naphrax-mounted diatom cells are also shown. The geographical distribution and ecological tolerance of F. saprophila is probably much wider than previously reported, but needs further investigation. The results of molecular phylogenetic analyses confirm the clear separation of Fistulifera Lange-Bertalot from Navicula Bory, also showing that its sister genera are Craticula Grunow, Eolimna Lange-Bertalot and Stauroneis Ehrenberg. Surprisingly, genera considered to have similar morphological characteristics, such as Mayamaea Lange-Bertalot and Sellaphora Mereschkowsky fall on a separate phylogenetic branch.