Phylogenetic significance of the characteristics of simple sequence
repeats at the genus level based on the complete chloroplast genome
sequences of Cyatheaceae
Abstract
Recent taxonomic and molecular phylogenetic studies have shown that
Gymnosphaera should be recognized as an independent taxonomic unit at
the genus level under the family Cyatheaceae. In this study, the
complete chloroplast genomes of the eight species of Cyatheaceae were
sequenced, and their phylogenetic relationships were reconstructed using
the maximum likelihood, Bayesian inference, maximum parsimony, and
neighbor-joining methods, and the characteristics of their simple
sequence repeats (SSRs) were compared and analyzed for the first time.
The results showed that when Cyatheaceae was divided into three
genera,the number, relative abundance, relative density, and GC content
of all SSRs and of SSRs of certain unit lengths in the chloroplast
genomes of the eight species of Cyatheaceae were genus specific in the
whole chloroplast genomes and in their different regions (large
single-copy, small single-copy, inverted repeat, intergenic spacer,
intron, rRNA gene, and coding sequence regions). The SSRs overall and
the single-nucleotide SSRs had significant differences in number,
relative abundance, relative density, and GC content between the
chloroplast genomes, their intergenic regions, and large single-copy
regions. When Cyatheaceae was divided into two genera, only the
difference in GC content was significant. Therefore, our results support
the restoration of the hierarchical status of Gymnosphaera. This study
provides an important basis for the identification of the phylogenetic
relationship of Cyatheaceae plants.