NEW SPECIES AND NEW COMBINATIONS IN THE GENUS SEMINAVIS (BACILLARIOPHYTA)

Abstract

A previous study, leading to the redefinition of Seminavis ventricosa (Gregory) Garcia-Baptista and some related taxa, made it clear that a considerable number of species exist within Seminavis D.G. Mann. Many species are still classified under Amphora Ehrenberg, although they clearly share common morphological features with Seminavis. Some of these species are described as new or transferred here, whereas others are only mentioned because of insufficient evidence, lack of original material, or poor documentation, so that taxonomic changes would be unwise at present. The species S. basilica Danielidis sp. nov., S. heidenii D.G. Mann sp. nov., S. strigosa (Hustedt) Danielidis & Economou-Amilli comb, nov., S. latior (A. Schmidt) Danielidis & D.G. Mann comb, et stat. nov., and S. obtusiuscula (Grunow) Danielidis & D.G. Mann comb. nov. all share the characteristic valve shape, areola structure and raphe constraction of typical Seminavis. Furthermore, in those species where fresh material was available, two plate-like, girdle-appressed chloroplasts were evident, as in other Seminavis and in almost all members of the Naviculaceae Kützing emend. D.G. Mann. The identity of S. cymbelloides (Grunow) D.G. Mann is discussed, although original material has not been available to us and may not exist. Lectotypes for A. angusta var. angustissima Van Heurck, A. diducta A. Schmidt, S. latior (A. Schmidt) Danielidis & D. G. Mann, and S. obtusiuscula (Grunow) Danielidis & D.G. Mann are also designated.