[Genetic structure of diploid-polyploid complex of spined loaches Cobitis (Cypriniformes, Cobitidae) of the Danube delta]

Abstract

The unusually high diversity of spined loache biotypes in Lower Danube was detected by means of biochemical genetic investigation and cytometric analysis of 358 specimens collected in riverbed and eriks. Along with two diploid species (C. elongatoides and C. "tanaitica") six hybrid forms were revealed: diploid C. elongatoides "tanaitica"; triploid C. 2 elongatoides--"tanaitica", C. elongatoides--2 "tanaitica" and C. 2 elongatoides--species-1 and tetraploid C. 3 elongatoides--"tanaitica", C. elongatoides--species-2--2 "tanaitica". Besides that the specimens with recombinant genotypes occured. In spite of the apomictic mode of reproduction the poliploids do not possess the clonal structure but according to the level of polymorphism and the genotype distribution are isomorphous to the parental diploid species. This means that on the contrary to the polyploid cobitids of the Dnieper which have appeared in this catchment area due to the expansion of their home range the polyploid fishes from the Lower Danube reaches are autochtonous and are produced as a result of hybridization with the local diploid species. The process is seemingly going on without any kind of limitations.