Studies in the Diatom Genus Hantzschia 3. Infraspecific Variation in H. virgata

Infraspecific variation has been investigated in the marineepipelic diatom Hantzschia virgata using light and electronmicroscopy. Although the variation pattern in this species iscomplex and to some extent discontinuous, allowing the recognitionon phenetic grounds of four or five discrete infraspecific taxaincluding vars. virgata (= H. insolita), gracilis, leptocephala(= capitellata) and wittii (= intermedia), it is concluded thatto split the species would be imprudent. Variation has beenfound not only in characters such as valve outline and size,or stria density, but also in ‘qualitative’ characterssuch as raphe, fibula and girdle structure, characters whichhave often been assumed to be constant within species, generaor taxa of higher rank: previous generalizations about the usefulnessof certain characters in distinguishing taxa of a given rankare seen to have been incautious. Hantzschia virgata (Roper) Grun., diatom taxonomy, infraspecific variation