Bitterlings are relatively small cypriniform species and extremely interesting evolutionarily due to their unusual reproductive behaviors and their coevolutionary relationships with freshwater mussels. As a group, they have attracted a great deal of attention in biological studies. Understanding the origin and evolution of their mating system demands a well-corroborated hypothesis of their evolutionary relationships. In this study, we provide the most comprehensive phylogenetic reconstruction of species relationships of the group based on partitioned maximum likelihood and Bayesian methods using DNA sequence variation of nuclear and mitochondrial genes on 41 species, several subspecies and three undescribed species. Our findings support the monophyly of the Acheilognathidae. Two of the three currently recognized genera are not monophyletic and the family can be subdivided into six clades. These clades are further regarded as genera based on both their phylogenetic relationships and a reappraisal of morphological characters. We present a revised classification for the Acheilognathidae with five genera/lineages: Rhodeus, Acheilognathus (new constitution), Tanakia (new constitution), Paratanakia gen. nov., and Pseudorhodeus gen. nov. and an unnamed clade containing five species currently referred to as "Acheilognathus". Gene trees of several bitterling species indicate that the taxa are not monophyletic. This result highlights a potentially dramatic underestimation of species diversity in this family. Using our new phylogenetic framework, we discuss the evolution of the Acheilognathidae relative to classification, taxonomy and biogeography.

Aquatic Life Conservation Research Center Research Institute of Environment Agriculture and Fisheries Osaka 572 0088 Japan

Biodiversity Research Center Academia Sinica Taipei 11529 Taiwan

Biodiversity Research Center Academia Sinica Taipei 11529 Taiwan; Department of Biological Science and Technology National Chiao Tung University Hsinchu 30068 Taiwan; Department of Biology Saint Louis University St Louis MO 63103 USA

Department of Biological Science and Technology National Chiao Tung University Hsinchu 30068 Taiwan; Institute of Bioinformatics and Systems Biology National Chiao Tung University Hsinchu 30068 Taiwan

Department of Biological Science Sangji University Wonju 220 702 Republic of Korea

Department of Biological Sciences Sungkyunkwan University Suwon 440 746 Republic of Korea

Department of Biology Saint Louis University St Louis MO 63103 USA

Department of Oceanography National Sun Yet sen University Kaohsiung 80424 Taiwan; Institute of Biodiversity Science Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering Fudan University Shanghai 200433 China

Institute of Oceanography National Taiwan University Taipei 10617 Taiwan

Institute of Vertebrate Biology Academy of Sciences of the Czech Republic Květná 8 603 65 Brno Czech Republic

Japan Wildlife Research Center Tokyo 130 8606 Japan

Key Laboratory of Aquatic Biodiversity and Conservation of Chinese Academy of Sciences Institute of Hydrobiology Chinese Academy of Sciences Wuhan 430072 China

Natural History Museum and Institute Chiba 260 8682 Japan

School of Biological Sciences Seoul National University Seoul 151 747 Republic of Korea

School of Biology University of St Andrews St Andrews Fife KY16 8LB UK; Institute of Vertebrate Biology Academy of Sciences of the Czech Republic Květná 8 603 65 Brno Czech Republic

References provided by Crossref.org

The impact of invasive Sinanodonta woodiana (Bivalvia, Unionidae) and mussel macroparasites on the egg distribution of parasitic bitterling fish in host mussels

Parasitic fish embryos do a "front-flip" on the yolk to resist expulsion from the host

Intensity-dependent energetic costs in a reciprocal parasitic relationship

Bayesian inference supports the host selection hypothesis in explaining adaptive host specificity by European bitterling

Population-specific responses to an invasive species