Polymorphism of the mitochondrial cytochrome b gene, phylogeography, and molecular adaptation of the Siberian salamander (Salamandrella keyserlingii, Amphibia, Caudata)

We performed an analysis of nucleotide variation of the mitochondrial DNA (mtDNA) cytochrome b gene in populations of the Siberian salamander ( Salamandrella keyserlingii Dybowski, 1870) from Khabarovsk krai; the Jewish autonomous oblast; Amur, Sakhalin, and Magadan oblasts; Sakha; and other regions of northern Eurasia. Two major phylogenetic haplotype groups, AB and C, were found using phylogenetic analysis. The degree of intergroup divergence is 1.87%, which indicates that these groups diverged about 1.5 Ma ago. Siberian salamanders with the AB haplogroup and with four of the five subgroups of the C haplogroups are found only in the Far East, including Sakhalin; the rest of the geographical range is occupied by one of the haplogroups, C1. Analysis of the distribution of nonsynonymous and synonymous substitutions demonstrated that the cytochrome b gene variation of the Siberian salamander is neutral. However, nucleotide sequences of the AB and C groups differ significantly in the region corresponding to the cd-loop of the Q 0 redox center of cytochrome b protein. In addition, the radical serine-to-leucine substitution in position 160 of the cd2-loop changes the physicochemical properties of the cd region of the C group sequences by increasing its hydrophobicity. The obtained results suggest that the changes in the sequence of the cytochrome b gene of the Siberian salamander group C are adaptive.