Morphology, taxonomy, biogeography and ecology of Micrasteriasfoliacea Bailey ex Ralfs (Desmidiales, Zygnematophyceae)

Micrasteriasfoliacea (Desmidiales, Zygnematophyceae) is an interesting desmid species as its filamentous life form is quite different from all other species within the genus. Due to the large size of the filaments and cells, accurate species identification is easy. After its original description from Rhode Island (USA) it was recorded from five continents, but no record could be found of its presence in Europe. In this paper a review of the worldwide distribution of M.foliacea (Desmidiales, Zygnematophyceae) is presented, together with notes on the species' ecology. In addition to its currently known geographical distribution, the paper also records the species' presence at two new locations in southern Africa, namely Botswana (Okavango River) and Mozambique (Palma, Cabo Delgado). The paper presents a discussion of taxonomical levels of intraspecific taxa, based on morphological characteristics. It is proposed that the taxonomical status of M.foliaceaBailey ex Ralfsf.nodosa should be raised to the variety, as its nodular cell wall thickenings are unique morphological features.