Study of the Polymorphism of ISSR Markers in Spined Loaches of the Genus Cobitis (Cobitidae) in Connection with Problems of Differentiation of the Species Involved in the Formation of Polyploid Forms of Hybrid Origin and Determination of Their Taxonomic Status

Abstract

Abstract We have analyzed the polymorphism of ISSR fragments of DNA by polymerase chain reaction in spined loaches for the first time. The analysis has made it possible to successfully differentiate the genomes, which were presumably involved in the formation of polyploid forms of hybrid origin: Cobitis taenia; spined loaches from the Danube River basin, which are diagnosed as C. elongatoides; C. tanaitica from the Don River basin and spined loaches from Lake Sinoe, which are also assigned to the species C. tanaitica by a number of authors. The following conclusions have been made based on comparative morphological studies of previously undifferentiated forms: (1) spined loaches from Central Europe with karyotype 2n = 50, NF = 96 correspond to the diagnosis of the species C. elongatoides; this species also differs from a number of closely related species and polyploid forms in the origin of the dorsal fin in front of the base of the pelvic fins, as well as in the presence of a spot in the lower half of the caudal fin base; (2) spined loaches from Lake Sinoe and other populations of Central Europe with karyotype 2n = 50, NF = 86 are nonconspecific to C. tanaitica and should apparently be ranked as an independent species, C. megaspila.