Investigations of the type materials of Achnanthes parallela J.R.Carter and Achnanthes petersenii Hustedt (Bacillariophyceae) with comments on the genus Rossithidium Round & Bukhtiyarova

ABSTRACT

Achnanthes parallela J.R.Carter was described from Lindean, Scotland, a freshwater species widely distributed in lochs of the southern Scottish uplands. It is currently regarded as a synonym of Achnanthes petersenii Hustedt first described from Svalbard. Investigation of type material for both taxa using light and scanning electron microscopy revealed that they are distinct species, and they can be distinguished using light microscopy alone. Current records of A. petersenii suggest a wider distribution in North America, Europe and Russia, but Achnanthes parallela and A. petersenii have not been distinguished in the past hence some records might require corrections. Based on our own observations, current discussions and a literature review, it is concluded that the two genera Rossithidium Round & Bukhtiyarova 1996 and Achnanthidium Kützing 1844 cannot yet be unambiguously defined on the basis of morphological criteria (discriminating characteristics) and there is insufficient molecular evidence to either support or reject the separation of these genera. On the basis of valve morphology and the match of characters with those in other species of Achnanthidium we propose the following combinations: Achnanthidium parallelum J.R.Carter ex Jüttner, D.M.Williams, Ector & C.E.Wetzel, sp. nov. and Achnanthidium petersenii (Hustedt) C.E.Wetzel, Ector, D.M.Williams & Jüttner, comb. nov.

KEYWORDS:

• Achnanthes
• Achnanthidium
• Bacillariophyta
• morphology
• Rossithidium
• type material

Acknowledgments

We would like to thank the curators at the diatom collections of the Natural History Museum, London, and at the Hustedt Collection, Alfred-Wegener Institute, Bremerhaven, for providing the loans of the type materials.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Funding was provided in the framework of the DIATOMS project (LIST - Luxembourg Institute of Science and Technology).

Notes on contributors

Ingrid Jüttner

Ingrid Jüttner is Principal Curator Botany at Amgueddfa Cymru-National Museum Wales and serves as the Secretary of the International Society for Diatom Research. Diatom applications in environmental assessments of freshwaters and taxonomic, ecological and biogeographical studies of the diatom flora of Britain and Ireland, the Himalaya and the Falkland Islands are the core of her research. She currently works on river restoration projects in Britain, and on high altitude lakes in the Himalaya.

Carlos E. Wetzel

Carlos E. Wetzel is a botanist and a researcher at the Luxembourg Institute of Science and Technology. He has authored and co-authored over 100 scientific articles dealing with diatoms in rivers, lakes and soils worldwide. Carlos has been teaching numerous training courses on diatom ecology and taxonomy designed for biologists, technicians and ecologists, contributing to the continuous improvement in the Water Framework.Directive implementation in Europe.

David M. Williams

David M. Williams is a diatomist at the Natural History Museum, London (BM), and he is President of the Systematics Association. He has authored nearly 200 papers and 10 books, mostly on diatom taxonomy, systematics and biogeography, as well as on systematic and biogeographic theory. He regularly teaches courses on diatom taxonomy and ecology to undergraduate and postgraduate students.

Luc Ector

Luc Ector is a botanist and senior researcher at the Luxembourg Institute of Science and Technology. He has written over 210 articles and worked on diatoms in rivers, lakes and soils for the last 30 years. He was the President of the “Association des Diatomistes de Langue Française (ADLaF)”. He organizes and teaches numerous training courses on diatom ecology and taxonomy designed for biologists, technicians and ecologists, contributing to the continuous improvement in the Water Framework Directive implementation in Europe.