The genus Navigiolum (Bacillariophyceae) in Mediterranean and North African rock pool habitats: description of four new species from Algeria

Four new species of the recently established genus Navigiolum (Naviculaceae, Bacillariophyceae) are described from samples collected in ephemeral rock pools of Algeria (North Africa). These species are compared with three similar taxa, recently described from comparable habitats In Sardinia (Italy). With a single exception, Navigiolum is Currently composed of species that can be considered endemic elements of the circum-mediterranean region and Of Unusual autecology. They are living in small freshwater pools that are Subject to extreme fluctuation. The seven Populations and several more from Sardinia and Algeria appear closely related under light microscopy but can be clearly distinguished in the scanning electron microscope. Four new species, Navigiolum marvanii, N. algeriense, N. simplex and N. densistriatum are proposed.