Caractérisation morphométrique et statistique de deux populations d' Aphanizomenon du groupe Aphanizomenon ovalisporum Forti des lacs de Nemi et Albano (Italie).

Two populations of filamentous Cyanophyta with elliptic akinetes from the lakes of Nemi and Albano (Latium, Italy) have been characterized morphometrically and statistically. These populations have been attributed to the genus Aphanizomenon on the basis of the subsymmetric structure of the trichomes. The Albano population resembles Aphanizomenon ovalisporum Forti and the Nemi population resembles Anabaena bergii Ostenfeld var. minor Kisselev. Their attribution to these species is however incertain. To avoid a wrong diagnosis or the uncontrolled creation of new species, an alternative method is proposed , based on an auxiliary concept, that is, the concept of "statistical species". This term does not indicate a species in the current meaning of the term but a population statistically defined, provisorily considered as a species and thus able to be designated with a name that distinguishes it from other populations.