The genus Marstoniopsis (Gastropoda : Rissooidea): intra- and intergenericphylogenetic relationships

Marstoniopsis scholtzi (A. Schmidt, 1856) and M. insubrica (Kuster, 1853), have been commonly accepted as distinct species, partly because of their al lopatric distribution patterns, but there appear to be no morphological dif ferences between them. Also the phylogenetic relationships of the genus Mar stoniopsis van Regteren Altena, 1936 remain enigmatic. In the present study the authors sequenced a fragment of the mitochondrial cytochrome oxidase I gene in representatives of three populations of M. scholtzi and one popula tion of ref insubrica to access the degree of genetic differentiation betwe en those taxa. A phylogenetic analysis was performed with representatives o f the families Hydrobiidae. Amnicolidae and Cochliopidae in order to test t he taxonomic position of Marstoniopsis. The specimens from the three populations of Marstoniopsis scholtzi differ f rom each other in only one or two observed substitutions in 638 by (= 0.152 -0.304%). Each one of them also differs from the specimen of Ill. insubrica in one or two observed substitutions (= 0.152-0.304%). Based on the extrem ely low genetic divergence and the lack of morphological differentiation we consider all populations to belong to one species, Marstoniopsis insubrica . Maximum likelihood analysis places the genus Marstoniopsis in the family Amnicolidae, close to the genera Erhaia and Amnicola.