Taxonomy of Two Calligonum Species Inferred From Morphological And Molecular Data

The taxonomy of some Calligonum species has been controversial due to overlapping morphological characters between species. Although C. ebinuricum and C. trifarium are currently distinguished by the number of rows of bristles on fruit ribs, the suitability of this character for taxonomic classification has been questioned. In this study, morphological characters were used in combination with sequences of the chloroplast ribulose-1,5-bisphosphate carboxylase large subunit (rbcL), chloroplast-encoded maturase K (matK), and nuclear ribosomal internal transcribed spacer (ITS) DNA regions to aid in classification. The results revealed that, except the achene shape, the mean value of eight morphological characters of C. trifarium were larger than those of C. ebinuricum. All the intraspecific variability of nine morphological characters of C. ebinuricum were larger than C. trifarium. Other than achene diameter, the rest of the intraspecific variability of eight morphological characters of C. ebinuricum were larger than the interspecific variability. All the morphological characters were not significant between between C. ebinuricum and C. trifarium. No rbcL or matK sequence variation was observed between C. ebinuricum and C. trifarium. ITS sequences of C. ebinuricum and C. trifarium differed at four sites, one of which was parsimony informative, and pairwise distances and standard errors were equal to 0.003 and 0.002, respectively. Based on our statistical analysis of fruit morphological characters, molecular data and same geographical area, we support the merger of C. ebinuricum and C. trifarium into a single species, C. ebinuricum.