Mitochondrial DNA variation and reticulate evolution of the genus Abies

The sequences of three regions of mitochondrial DNA (mtDNA) of a total length of 5226 bp were used to study the phylogeography of the genus Abies. The mtDNA haplotype network, comprising 36 studied Abies taxa, consisted of two branches; the first represented all American species plus two Asian, and the second included the remaining Eurasian species. Within these clusters, the haplotypes formed nine major groups, generally corresponding to the clades of the previously obtained phylogeny based on chloroplast DNA (cpDNA), but the relationships of these groups were significantly different; species assignment to the particular mtDNA haplotype group was more in line with its geographical distribution. In addition, the mtDNA haplotype network contains cycles indicating the recombination. It is assumed that the incongruence of cpDNA and mtDNA phylogenies is caused by the introgression capture of alien mtDNA during species hybridization and thus contains information about past migrations. The cases of incongruence of mitochondrial and chloroplast DNA suggesting a migration of Abies between Asia and North America are discussed.