Phylogenetic use of noncoding regions in the genus Gentiana L.: chloroplast trnL (UAA) intron versus nuclear ribosomal internal transcribed spacer sequences

Abstract

Sequence divergence was estimated within noncoding sequences of both chloroplast DNA (cpDNA) trnL (UAA) intron and nuclear ribosomal DNA (nrDNA) internal transcribed spacer sequences (ITS1 and ITS2) for 10 species of the genus Gentiana L. (Gentianaceae). Comparisons of evolutionary rates among these sequences (cpDNA versus nrDNA, ITS1 versus ITS2) were performed. It appears that sequence divergence is on average two to three times higher in ITSs than in the trnL intron sequences and higher in ITS1 than in ITS2. Both the cpDNA intron and ITSs of nrDNA give concordant phylogenetic trees. However, the ITS-based phylogeny displays higher bootstrap values. At the intrageneric level, at least in Gentiana, ITSs (especially ITS2) sequences seem to be more appropriate in the assessment of plant phylogenies. Nevertheless, the cpDNA trnL intron seems to be preferable at the intergeneric level.