Phycological Research 2006; 54: 99–103 Blackwell Publishing AsiaMelbourne, AustraliaPREPhycological Research1322-08292006 Japanese Society of PhycologyJune 200654299103Original Article Fragilaria rumpensA. Tuji and D. M. Williams *To whom correspondence should be addressed. Email: tuji@kahaku.go.jp Communicating editor: K. Okuda. Received 24 June 2005; accepted 26 October 2005. Examination of the type material of Synedra rumpens = Fragilaria rumpens, Bacillariophyceae Akihiro Tuji 1 * and David M. Williams 2 1 Department of Botany, The National Science Museum, Tokyo 4-1-1, Amakubo, Ibaraki, 305-0005, Japan; and 2 Department of Botany, The Natural History Museum, London, Cromwell Road, London, SW7 5BD, UK SUMMARY Fragilaria rumpens (Kütz.) G. W. F. Carlson is assumed to be a cosmopolitan species, and is often reported from ponds and lakes. Nevertheless, this species is similar to both Fragilaria capucina Desm. and Fragilaria vaucheriae (Kütz.) J. B. Petersen and, as a conse- quence, the taxonomy of all three species has been confusing. In an attempt to solve the taxonomic prob- lems within this group, we have examined the type material of Synedra rumpens and discuss the differ- ences between it and some of those species said to be similar. Key words: Fragilaria rumpens, morphology, nomencla- ture, Synedra rumpens, taxonomy. INTRODUCTION Synedra rumpens Kütz. was described by Kützing (1844) from ‘Brackwasser der oldenburgschen Küste’. Carlson (1913) transferred this taxon to genus Fragi- laria. Hustedt (1930) presented this taxon in his famous monograph. However, the form presented in this monograph was quite different from type individu- als (see Krammer & Lange-Bertalot 1991 table 110, fig. 22). Patrick and Reimer (1986) also presented this taxon using the US material. This taxon is presumed to be a cosmopolitan and common tychoplanktonic-benthic species, reported from many freshwater lakes or ponds or slow-flowing streams (Patrick & Reimer 1986). Yet, the species is very similar to both Fragilaria capucina Desm. and Fragilaria vaucheriae (Kütz.) J. B. Petersen, and, hence, its taxonomy has been confusing. For example, Lange-Bertalot in Krammer and Lange-Bertalot (1991) examined the type materials of these taxa and consid- ered F. rumpens to be part of the F. capucina complex, which at that time was composed of 14 ‘Sippen’. Although the new combination ‘Fragilaria capucina var. rumpens (Kützing) Lange-Bertalot’ was proposed, it is not validly published as no basionym was cited. Later, Lange-Bertalot (1993) proposed a different combina- tion, Fragilaria capucina ssp. rumpens (Kütz.) Lange- Bert. and, later still, Lange-Bertalot, in the revised edition of Krammer and Lange-Bertalot (1991, 2000), used the specific name Fragilaria rumpens (Kütz.) Carlson for this taxon. Nomenclature aside, the morphological variation of F. rumpens was thought to be very large (Krammer & Lange-Bertalot 1991), although it was acknowledged that ecologic difference between F. rumpens and F. capucina existed: F. rumpens is a tychoplanktonic- attached species, whereas F. capucina is attached. Therefore, it is important to be able to distinguish these species if they are significant for ecologic studies. In the present paper, we report and document the morphology of F. rumpens as understood from the type material. We also discuss the differences between it and similar, presumably related, taxa. MATERIALS AND METHODS Two samples were examined: 1 Original type material (isotype) from the labeled packet 194 in the Kützing collection in the Dr Henri Van Heurck Museum, Antwerpen (AWM) and the Department of Botany, the Natural History Museum, London (BM). 2 Slide BM 18357 prepared from material in Kützing packet 194. RESULTS Fragilaria rumpens (Kütz.) G. W. F. Carlson (1913). Basionym: Synedra rumpens Kütz., Bacill. 69. pl. 16. f. VI. 4, 5. Synonyms: Fragilaria capucina var. rumpens (Kütz.) Lange- Bertalot in Krammer et Lange-Bertalot (1991) (nom. invalid). Fragilaria capucina ssp. rumpens (Kütz.) Lange- Bertalot (1993).