Incomplete Concerted Evolution of nrDNA ITS in Cornus subg. Syncarpea (Cornaceae)

Abstract:

The subgenus Syncarpea, which belongs to genus of Cornus (Cornaceae), includes five species and eight subspecies in China. nrDNA ITS sequences of 21 individuals from 4 species, with 1 to 2 populations for each species, in the subgenus were amplified and used to test the existence of incomplete concerted evolution and pseudogenes. Intra-genomic polymorphism was detected in the internal transcribed spacer (including ITS1, 5.8S and ITS2) regions of these species. The analyses of G+C content, 5.8S conserved motifs and minimum free energy of 5.8S secondary structures suggested that there were putative pseudogenes of nrDNA in these species. Phylogenetic analyses of the sequences resulted in five clades with variants from the same accession commonly being placed in two or more clades and species were grouped differently among clades. These results demonstrated the existence of incomplete concerted evolution of ITS within individuals of Syncarpea, which could be explained by incomplete lineage sorting, possible hybridization or polyploidy and resulted in the polymorphism of ITS and the difficulty in morphology-based species delineation in the subgenus.

Key words:Cornus subg. Syncarpea;nrDNA ITS;Incomplete concerted evolution;Pseudogenes