| 2) These freshwater species can be classified in three artificial groups: (a) the G. pulex-group (species without dorsal carina and with dense setation on pereiopods 3 and 4 and uropod 3), (b) the G. balcanicus-group (species without dorsal carina and poorly setose pereiopods 3 and 4 and uropod 3) and (c) the G. roeseli-group (species with dorsal carina). These groups are merely artificial ones since transitive (intermediate) species do exist. Moreover, the origin of the species is not known, so that polyphyly is not excluded. 3) In the present work the Gammarus pulex-group is revised, based on rich material from Europe, North Africa, Asia minor and adjacent areas. 4) The taxonomic differences between the various species are usually small but distinct and... |
