Molecular data reveal distinct phylogenetic position of Cottus metae, establish its distribution range, and invalidate the species status of C. scaturigo

The sculpins Cottus metae and C. scaturigo have previously been distinguished morphologically from C. gobio and described as distinct species. In the present study, sculpin samples from numerous sites covering the proposed range of C. metae and C. scaturigo, including unexamined adjacent sites that include topotypic specimens and other sculpins, were examined to determine whether they represent phylogenetically distinct units and to determine the geographical limits of the distribution of C. metae. Using two types of marker-the mitochondrial control region and the nuclear large subunit of the ribosomal RNA gene-we found high statistical support for C. gobio and C. metae forming two distinct clades. A sister relationship between C. gobio and C. metae was observed but also indicating, by analogy to the well-established status of the former, that the latter is a distinct species. However, this conclusion does not apply to C. scaturigo as the sample from the type locality clustered with C. gobio. A survey of numerous sculpin localities in Slovenia and adjacent areas, including the Drava river system, found that C. metae populates only the Sava river system, from the headwaters in NW Slovenia to the Medvescak Stream at Zagreb, Croatia. However, further downstream in the Kolpa River, and also in the Lonja and Una river systems, the next two tributaries to the Sava River, a sculpin population genetically distinct from both C. metae and C. gobio was found.