GENETIC-STRUCTURE AND ORIGIN OF A TETRAPL OID TOAD SPECIES BUFO-DANATENSIS PISANETS, 1978 (AMPHIBIA, BUFONIDAE) FROM CENTRAL-ASIA - DESCRIPTION OF BIOCHEMICAL POLYMORPHISM AND COMPARISON OF HETEROZYGOSITY LEVELS IN DIPLOID AND TETRAPLOID SPECIES

Comparison of individual variation at 24 biochemical loci in members o f the species complex of Palearctic green toads showed that the hetero zygosity of the tetraploid species Bufo danatensis (H(obs) + 0.45) was significantly higher than that of the diploid species B. viridis, B. sp., and B. raddei (H(obs) = 0.009 - 0.103). Such difference can be ex plained only by a hybrid origin of the tetraploid species. Individual electrophoretic variability of the polyploid toad species is associate d with an allelic variation that is manifested in constantly heterozyg ous spectra as the gene dosage effect. At the population level, this p henomenon found in Pamir toads is caused by irregular meiosis in found ers of the population or by directional changes in gene regulation. Ge notypic distributions in zones of contact of the diploid and tetraploi d taxons demonstrate the possibility of restricted introgressive hybri dization.