Mitochondrial DNA variation was investigated in 11 populations Abies sachalinensis in Sakhalin and Kunashir Islands. Variation in the third intron of the nad4 gene was measured with the analysis of restriction fragments length polymorphism using HinfI enzyme. Three haplotypes were found in Sakhalin fir in total. Populations of northern Sakhalin contain only haplotype n which is fixed in mainland fir A. nephrolepis (Trautv.) Maxim. Haplotype n is distributed allover the studied territory except the south-western part of the Sakhalin and the Kunashir Island. Haplotype s is fixed in Kunashir, dominates in southern Sakhalin, and spread over central Sakhalin populations. Haplotype m was met in one stand in the South Sakhalin (Makarov).

Obtained geographic distribution of mitochondrial haplotypes in A. sachalinensis corresponds to the structure of allozyme variation (Semerikova, Semerikov, 2007; 2008) and to the morphological data (Buhteeva, 1963). Thus, mitochondrial and allozyme markers describe the transitional zone between A. nephrolepis and typical, specific to south Sakhalin A. sachalinensis explainable by secondary contact between two closely related taxa followed by introgressive hybridization.

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