Examination of the type materials of diatoms described by Hohn and Hellerman from the Atlantic Coast of the USA

Abstract

In 1966, Matthew Hohn and Joan Hellerman described 44 diatom species from one freshwater and several coastal habitats along the Atlantic coast of the USA. The goal of our study was to examine the type materials of these species and to evaluate their taxonomic status. Type specimens of 32 taxa were located and documented with light microscopy, and of these, 16 were investigated further with scanning electron microscopy. Twelve taxa described by Hohn and Hellerman (Achnanthes recava, Amphiprora incompta, Amphora bicapitata, A. delapunctata, A. pleniluna, Coscinodiscus bulla, Navicula bifax, N. scala, N. taraxa, Nitzschia sigma var. undulata, N. cryptostriata and Synedra ridica) were found to be taxonomic synonyms of diatoms described prior to 1966, whereas five taxa (Amphora allanta, Biddulphia inusitata, Cocconeis nugalas, Fragilaria silendum and F. virescens var. torus) were re-described later by other authors. Four new combinations are made here: Neodelphineis silenda (Hohn & Hellerman) Desianti & Potapova, Pleurosira inusitata (Hohn & Hellerman) Desianti & Potapova, Staurophora agmastriata (Hohn & Hellerman) Desianti & Potapova and Staurophora cumvibia (Hohn & Hellerman) Desianti & Potapova. Lectotypes are designated for Amphora adumbrata, A. delapunctata and Gyrosigma incompta. An epitype is designated for Surirella striatula var. spinifera. Taxonomic placement of seven taxa documented here (Achnanthes radiatus, Coscinodiscus litos, Cymbella cassidula, Fragilaria pelta, Navicula delastriata, N. impertila and N. lumbricastriata) remains unclear because their type populations are extremely sparse and type specimens do not provide sufficient morphological data. This study is a necessary step in clarifying species identities and describing diatom diversity in coastal habitats.

Keywords:

• type material
• ANSP
• coastal
• diatoms
• new combinations

Acknowledgements

We are thankful to Dr Michael Sullivan for his help with some taxonomic issues and two anonymous reviewers and associate editor Dr Mark Edlund for their constructive comments that greatly helped to improve this paper. The use of the Centralized Research Facilities, Drexel University, for the SEM is gratefully acknowledged.