Molecular phylogenetic analysis of the genus Abies (Pinaceae) based on the nucleotide sequence of chloroplast DNA

A phylogenetic study of firs (Abies Mill.) was conducted using nucleotide sequences of several chloroplast DNA regions with a total length of 5580 bp. The analysis included 37 taxa, which represented the main evolutionary lineages of the genus, and Keteleeria davidiana. According to phylogenetic reconstruction, the Abies species were subdivided into six main groups, generally corresponding to their geographic distribution. The phylogenetic tree had three basal clades. All of these clades contained American species, and only one of them contained Eurasian species. The divergence time calibrations, based on paleobotanical data and the chloroplast DNA mutation rate estimates in Pinaceae, produced similar results. The age of diversification among the basal clades of the present-day Abies was estimated as the end of the Oligocene-beginning of Miocene. The age of the separation of Mediterranean firs from the Asian-North American branch corresponds to the Miocene. The age of diversification within the young groups of Mediterranean, Asian, and boreal American firs (A. lasiocarpa, A. balsamea, A. fraseri) was estimated as the Pliocene-Pleistocene. Based on the phylogenetic reconstruction obtained, the most plausible biogeographic scenarios were suggested. It is noted that the existing systematic classification of the genus Abies strongly contradicts with phylogenetic reconstruction and requires revision.