Phylogeny of the genus Salix L. (Salicaceae) in the Russian Far East

Vyacheslav Yu. BARKALOV & Marina M. KOZYRENKO
Institute of Biology and Soil Science FEB RAS, Vladivostok, Russia

Recent studies based on sequencing nuclear and chloroplast DNA genomes show that genera Salix, Toisusu and Chosenia form a monophyletic group. Evolutionary relationships in this group still remain arguable. To determine phylogenetic relationships in the genus Salix we researched ITS of an nDNA region and 7 chDNA regions. Nucleotide sequence analysis of ITS region did not allow us to solve relationships of species in the genus, except for the big subgenus Salix (sections Amygdalinae, Urbanianae, Pentandrae, Salix, Subalbae, Longifolia). 11 chDNA regions showed irregular variation. The rbcL gene part proved to be the most conservative: all researched Salix species in NE Asia had the same sequence. Most variable were the regions of trnD–trnT and rpoB–trnC. Overall length of combined sequences of studied chDNA regions (including indels) was 7 408 pm (5 % of a plastid genome) for each sample. ChDNA variation in researched taxa is low. We discovered 193 variable sites (2.6 %), of which 95 were informative according to the Method of Maximum Parasynonymy and 98 uninformative. Analysis of 66 sequences revealed 56 haplotypes of which 52 are unique. 14 species in subgenera Chamaetia and Vetrix have the same haplotype. Largest genetic distance is between S. nipponica and S. pseudopentandra (0.014). Molecular differences were found only among species of subgenus Salix, showing high divergence of their chloroplast genomes. The high similarity of sequences in chDNA and ITS region, found in most Salix species, may provide evidence of their recent and rapid divergence from a common ancestor, as well as of a high level of interspecies hybridization.

© 2012 Organizing Committee