Phylogeography and demographic history of Siberian rubythroat Luscinia calliope

Phylogeographic analysis on the basis of individual marker variability provides insight into the history and mechanisms of the range formation of widely distributed species. A preliminary study of the mtDNA cytochrome b gene in Siberian rubythroat Luscinia calliope revealed the existence of three well-differentiated haplogroups, including one western and two eastern haplogroups. Continuing the study of the genetic markers of the species, we found that, in western part of the range, represented by the nominative geographic race, there were almost exclusively haplotypes of western group. In eastern populations of Khabarovsk krai, Chukotka, Kamchatka, and Sakhalin, haplotypes of all groups are mixed in different proportions. At the same time, the populations of Hokkaido and Iturup islands are exclusively represented by individuals with eastern haplotypes. Comparison of the identified nuclear copies of mitochondrial genes and construction of the phylogenetic network of haplotypes on the basis of cloned and initial sequences showed that two groups of eastern haplotypes (one of which geographically corresponded to L. c. anadyrensis and L. c. camtschatkensis and the second corresponded to L. c. sachalinensis) originated from nuclear pseudogenes of L. c. calliope through intergenomic recombination. In this regard, we propose a new hypothesis for the establishment of the modern range of this species, according to which the Siberian rubythroat dispersal from South Siberia occurred in two stages. At first, the species expanded its range to the northeast in the direction of the Kolyma and Koryak uplands. During the settling of these areas of northeastern Asia, a recombination between the mitochondrial and nuclear DNA took place, which led to the forming of a new haplotype, which was widespread in the emerging breeding populations. Birds with recombinant haplotypes populated the territories of Chukotka and Kamchatka, and then gradually occupied the Kuril Islands and, eventually, reached Hokkaido. At the next stage, Siberian rubythroat, probably, appeared in Sakhalin Island during spring migration, where some individuals stopped for breeding. Settling of the island was accompanied by similar intergenomic recombination and rapid fixation of a new recombinant haplotype with its subsequent spread across Sakhalin. The insular way of dispersal is completely repeated by modern migrants.