Daphnia (Ctenodaphnia) mediterranea Alonso, 1985 (Crustacea: Cladocera) as a Mediterranean species penetrating also the Ponto-Caspian region, a rare case for the cladocerans

The aim of this communication is to report on our discovery of a population of Daphnia (Ctenodaphnia) mediterranea Alonso, 1985 in the Kalmyk Republic representing a new record for the fauna of Russia and demonstrating the presence of this Mediterranean taxon in the Ponto-Caspian Region. Genetic information on our D. (C.) mediterranea from Kalmykia was obtained from a single specimen subjected to a complete genome study.

Previously it was shown that D. (C.) mediterranea belongs to the Major Clade 2 of D. (Ctenodaphnia). Here we have demonstrated, based on two mitochondrial loci (fragments of 12S + COI genes), the existence within the latter of a remarkable Sub-clade 2, containing at least three species with very distant distribution ranges but with a similar biology: they inhabit mainly “refugial” brackish waters, and D. (C.) mediterranea belongs there.

Evolution of the latter seems to be related to Paratethys basin evolution. We can hypothesize that the lowlands around Paratethys (and its subsequent remains) have provided the populations of aquatic invertebrates with numerous shallow water bodies with different salinities, including those with a high mineralization, which now represent a home of D. (C.) metiterranea.