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.
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