Intraspecific or interspecific variation: delimitation of species boundaries within the genus Gammarus (Crustacea, Amphipoda, Gammaridae), with description of four new species

The delineation of Gammarus species is controversial because of extensive intraspecific morphological variation. The current study examined DNA sequences from the mitochondrial cytochrome c oxidase subunit I and the nuclear 28S genes as well as morphological and ecological data to determine the species boundaries of Gammarus species from China. The results of molecular analyses showed that Gammarus sp1, G. sp2, G. sp3, and G. sp4 are monophyletic and deeply divergent from sister groups. Detailed morphological and ecological comparisons with closely related species were consistent with molecular analyses. Gammarus sp1, G. sp2, G. sp3, and G. sp4 were described as four new species: Gammarus illustris sp. nov., Gammarus clarus sp. nov., Gammarus hypolithicus sp. nov., and Gammarus parvioculus sp. nov. We recommend that molecular detected species should be formally named and described for future research. (C) 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160, 215-253