Phylogeography and molecular adaptation of Siberian salamander Salamandrella keyserlingii based on mitochondrial DNA variation

We assessed the phylogeographic pattern of Siberian salamander (Salamandrella keyserlingii, Dybowski, 1870), which appear to be the most northern ectothermic, terrestrial vertebrate in Northern Eurasia, by sequence analysis of a 611-bp fragment of the mitochondrial cytochrome b gene in 159 specimens from different localities (Khabarovsk region, Sakhalin, Yakutia, Magadan region, Chukotka, Kamchatka and others). The data revealed that cytochrome b lineages of S. keyserlingii are divided into haplogroups A, B and C. Haplogroup A and B sequences are widespread in the Far East region, whereas haplogroup C consisting of several phylogenetic clusters (C1, C2, C3) is present in the all range of S. keyserlingii. Among them, cluster C3 appears to be specific for Sakhalin; most likely, it has arisen in situ in this island, with the entry time of the founder mtDNA estimated at about 0.4 MY. Analysis of cytochrome b gene variation by using different neutrality tests (including those based on KA/KS-ratio) has shown that differences between haplogroups were statistically insignificant, thus suggesting selective neutrality. However, analysis of amino acid changes allowed us to detect a signature of molecular adaptation, which might have led to appearance of adaptive cytochrome b variants in haplogroup C, originating most likely at the end of Eopleistocene (about 0.64 MY based on the haplogroup C divergence level). It seems probable that this adaptive mechanism could promote subsequent populating of new regions.