Molecular phylogeny of icefish Salangidae based on complete mtDNA cytochrome b sequences, with comments on estuarine fish evolution

Phylogenetic relationships among 15 species in the family Salangidae were constructed based on the complete cytochrome b sequence (1141 bp). We confirmed the monophyly of the family Salangidae and defined four primitive lineages within this family: (I) Protosalanx , Neosalanx anderssoni , Neosalanx tangkahkeii , and Neosalanx argentea ; (II) Neosalanx reganius , Neosalanx jordani , Neosalanx oligodontis , and Neosalanx  sp.; (III) Hemisalanx , Salanx , Leucosoma , and Salangichthys ishikawae ; and (IV) Salangichthys microdon . A major finding of our study is the key basal placement of Sg. microdon . According to the tentative estimation, the divergence of the four lineages appears to have been initiated in the early Miocene (21 Mya), with most speciation events occurring 1.05–9.90 Mya. Taxonomic revisions on subfamilial, generic, and specific levels were carried out based on phylogenetic relationships and genetic distance, taking into account some key morphological characters. The speciation mechanism in Salangidae is also discussed, and the evidence shows that geographical isolation, water mass, as well as some ecological factors, may not always play important roles in the speciation of temperate estuarine fish. In the most cases, sympatric salangids are not monophyletic, indicating that their coexistence reflects secondary contact rather than sympatric speciation.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 327–342.