Species of the genus Daphnia O.F. Müller, 1785 (Cladocera: Daphniidae) have become very important models in evolutionary biology research. Previous morphological and genetic evidence suggests that numerous closely related "species groups" exist within the subgenus Daphnia (Ctenodaphnia) Dybowski & Grochowski, 1895, containing both described and undescribed species. The Daphnia similis group is among these species groups. The aim of the present paper is to revise the taxonomy of the Daphnia (Ctenodaphnia) similis group in the Old World with both morphological and genetic evidence (based on mitochondrial COI and 12S rRNA genes). We found that there are at least four species in the Old World D. similis species group: D. similis Claus, 1876; D. sinensis Gu, Xu, Li, Dumont et Han, 2013; D. similoides Hudec, 1991 and D. inopinata sp. nov. These four taxa of the similis-group, confused previously with D. similis, have different distributional ranges in the Old World, from extremely wide, spanning several biogegraphic regions (as D. sinensis), to regional endemics (D. similoides) and even species known so far from a single locality (D. inopinata sp. nov.). The Daphnia similis group provides another example in the cladocerans whereby the study of males yields more valuable characters for taxonomy than the study of parthenogenetic females.

A N Severtsov Institute of Ecology and Evolution Leninsky Prospect 33 Moscow 119071 Russia; Email

A N Severtsov Institute of Ecology and Evolution Leninsky Prospect 33 Moscow 119071 Russia; Email unknown

Department of Biological Sciences The State University of New York at Buffalo Buffalo NY 14260; Email unknown

Department of Ecology Faculty of Science Charles University Prague Viničná 7 Prague 2 CZ 128 44 Czech Republic; Email unknown

N K Koltzov Institute of Developmental Biology Vavilova Str 26 Moscow 119334 Russia; Email unknown

Papanin Institute for the Biology of Inland Waters Russian Academy of Sciences Borok 152742 Yaroslavl Area Russia; Email unknown

Research Institute for Nature and Forest Gaverstraat 4 9500 Geraardsbergen Belgium; Email unknown

White Sea Biological Station Biological Faculty M 5 Lomonosov Moscow State University Leninskie Gory Moscow 119991 Russia; Email unknown

References provided by Crossref.org

Unexpected mitochondrial lineage diversity within the genus Alonella Sars, 1862 (Crustacea: Cladocera) across the Northern Hemisphere

Divergent clades or cryptic species? Mito-nuclear discordance in a Daphnia species complex