Analysis of the type of Fragilaria construens var. subsalina (Bacillariophyceae) and description of two morphologically related taxa from Europe and the United States

Abstract

Cejudo-Figueiras C., Morales E.A., Wetzel C.E., Blanco S., Hoffmann L. and Ector L. 2011. Analysis of the type of Fragilaria construens var. subsalina (Bacillariophyceae) and description of two morphologically related taxa from Europe and the United States. Phycologia 50: 67–77. DOI: 10.2216/09-40.1

Fragilaria construens var. subsalina is a common diatom found in a wide variety of aquatic systems worldwide. It was described by Hustedt (1925) from brackish waters in Oldesloe, Germany; a lectotype specimen was established by Simonsen (1987). We analysed the ultrastructure of specimens from the lectotype material by means of light (LM) and scanning electron microscopy (SEM) and show that this taxon should be placed at the species level within the genus Pseudostaurosira (as Pseudostaurosira subsalina). A similar but distinct taxon from the United States, found in waters with low electrolyte content, is proposed as a new species of Pseudostaurosira, namely Pseudostaurosira americana sp. nov. We also describe a second new species from Spain (Pseudostaurosira alvareziae sp. nov.), found in waters with moderate conductivity, which was misidentified as P. subsalina in the past. A morphometric analysis of the valve shape supports the morphological separation between the three species. The present study clarifies the taxonomy, ecology and systematic position of these three taxa and provides a comparison with other, similar taxa.

Key Words::

• Bacillariophyta
• Diatoms
• Fragilariales
• Lectotype
• Morphometry
• New species
• Pseudostaurosira

ACKNOWLEDGMENTS

This study was financed by the Public Research Centre – Gabriel Lippmann (Luxembourg), the University of León (Spain) and the Duero Basin Water Agency (Confederación Hidrográfica del Duero, CHD). Type material of P. subsalina was obtained from F. Hinz (Alfred-Wegener-Institut für Polar- und Meeresforschung) and the type material of P. americana from the United States was collected by Study Unit Biologists of the NAWQA program and kindly provided by Dr M. Potapova, ANSP Diatom Herbarium. We thank C. Bouillon and M.H. Novais for technical and SEM assistance. EAM thanks the CRP-Gabriel Lippmann, especially L. Ector, for the opportunity provided for a short visit to do taxonomic work. Support provided by the Administrative Council of the Association des Diatomistes de Langue Française to assist to the 27th Colloquium ADLaF in Dijon, France, made in part such a visit possible. EAM also thanks the Academy of Natural Sciences of Philadelphia, especially Dr D. Charles, for continued support. Dr K. Sabbe and two anonymous referees are thanked for their valuable comments on the manuscript.