Discovery of a New Species of Daphnia (Crustacea: Cladocera) from the Arabian Peninsula Revealed a Southern Origin of a Common Northern Eurasian Species Group

The biodiversity distribution patterns and their formation history in continental waters are studied based on some model groups such as Daphnia O.F. Müller (Crustacea: Cladocera). Most publications on this genus concern the subgenus Daphnia (Daphnia) while representatives of the subgenus Daphnia (Ctenodaphnia), inhabiting mainly temporary waters, are poorly studied. We found a new species of the D. (C.) sinensis complex in the deserts of the Arabian Peninsula, and our discovery allows us to resolve some problems concerning the history of these daphniids in the northern hemisphere. A formal description, illustrations (including numerous SEM photos) and a differential diagnosis of D. (C.) arabica Neretina, Al Neyadi & Hamza sp. nov. are provided. Phylogeny of D. (C.) similis complex is reconstructed based on three mitochondrial genes (12S, 16S and COI); a haplotype network based on short 12S fragments is also constructed. A monophyletic D. (C.) sinensis within the D. (C.) similis complex includes three earlier-derived locally distributed members: D. (C.) similoides, D. (C.) inopinata and D. (C.) arabica sp. nov. Our data suggest an old (Late Mesozoic) Gondwanan origin of the D. (C.) sinensis group and its Caenozoic differentiation in North Africa and the Middle East. This region then became a center of subsequent dispersion of D. (C.) sinensis through the whole of Eurasia and Africa during the Miocene and subsequent epochs. Interestingly, our scheme of the D. sinensis group dispersion has a well-known analogue: it is comparable to that suggested for earlier human migration from Africa through the Arabian Peninsula and the Middle East to the rest of Eurasia.