The phylogenetic relationships of "predatory water-fleas" (Cladocera: Onychopoda, Haplopoda) inferred from 12S rDNA.

Within the Cladocera, the water-fleas, four major taxa can be distinguished: Anomopoda, Ctenopoda, Haplopoda, and Onychopoda. Haplopoda and Onychopoda are called "predatory water-fleas." The Haplopoda is monotypic; its only representative, Leptodora kindtii, is common in palearctic and nearctic freshwater bodies. The Onychopoda show a remarkable geographic distribution. Most of the described species are restricted to the Caspian Sea, the Aral Sea, and peripheral areas of the Black Sea, including the Sea of Azov--all remnants of the Eastern Paratethys. The remaining onychopods are either freshwater inhabitants or marine animals, widespread in the world oceans. We present molecular evidence for a sister group relationship between Haplopoda and Onychopoda within the Cladocera. The Onychopoda and its three families are monophyletic. We suggest an independent invasion into the Ponto-Caspian basin at least three times, twice originating in the palearctic freshwater bodies and once starting from the world oceans. Copyright 2001 Academic Press.