A new species complex of Daphnia (Crustacea, Cladocera) from the Pacific Northwest of the United States

The genetic characterization of more than 1500 populations belonging to the Daphnia pulex group from the United States and Mexico revealed nine previously unrecognized species. Three of these taxa, showing morphological and genetic affinities, are newly described in this paper and are assigned membership in a new species complex. These species share a unique configuration of P-3 sensilla and a triangular ephippial shape which differs from that of other members of the genus Daphnia. All three species are large-bodied forms showing distinctive setulation of the internal margin of the ventral carapace. All these members of the complex appear to be narrow endemics, restricted to temporary ponds in semi-arid areas of the Pacific Northwest.