Neidiopsis hamiltonii sp. nov., N. weilandii sp. nov., N. levanderi and N. wulffii from western North America

Abstract

Neidiopsis hamiltonii sp. nov. and Neidiopsis weilandii sp. nov. are described from a stream, lakes and ponds in western North America. The new species are readily distinguished from the three other published species of Neidiopsis by valve size, valve shape and the nature of the proximal raphe ends. In both new species, loculi along the valve margins are continuous and form hollow longitudinal canals, as in Neidium. Diagnostic features common to all five Neidiopsis species include: (1) a mix of uniseriate and biseriate striae; (2) striae arranged in two offset ranks; (3) distal raphe fissures simple (not bifurcate); (4) habitat restricted to cold oligotrophic streams, lakes and ponds with low conductivity; and (5) distribution limited to the Arctic, sub-Arctic and alpine zones of temperate regions in the northern hemisphere. Considerable variation in valve shape, including apical shape, is demonstrated in Rocky Mountain populations of N. hamiltonii, N. levanderi (Hustedt) Lange-Bertalot & Metzeltin and N. wulffii (Petersen) Lange-Bertalot. A comparison of morphometric data for various populations of N. levanderi and N. wulffii indicates that valves from the Rocky Mountains tend to be larger than valves from European and more northerly North American populations.

Keywords:

• diatoms
• Neidiopsis
• Neidium
• Cascade Mountains
• Rocky Mountains
• North America
• Colorado
• Montana
• Washington
• Canada
• Bacillariophyceae
• taxonomy

Acknowledgements

I thank Mark Edlund and Eileen Cox for their valuable comments and generous assistance. Two anonymous reviewers provided several helpful suggestions for improving the paper. Marge Penton, John Pierce, and Craig Weiland collected the type materials. Jim Driver assisted with the capture of SEM images. Electron microscopy services and resources were provided by the Electron Microscopy Facility, Division of Biological Sciences, University of Montana, Missoula. The EM Facility is supported, in part, by grant #RR-16455-04 from the National Center for Research Resources (Biomedical Research Infrastructure Network program), National Institutes of Health.