A phylogeny of Calligonum L. (Polygonaceae) yields challenges to current taxonomic classifications

Calligonum is the only C4 genus within Polygonaceae. We applied DNA sequences from nuclear ribosomal internal transcribed spacer (nrITS) and five plastid genome regions (psbA-trnH, ycf6-psbM, trnL-F, rpl32-trnL rbcL) to reconstruct phylogeny of Calligonum. The nrITS combined were analysed separately. supports treatment mongolicum complex as a single species with intra-specific geographic structure, suggests independent hybrid origins for polyploid C. caput-medusae arborescens through comparisons tree. detected phylogenetic incongruence between trees hypothesized reticulate evolution or speciation in genus. Divergence time dating based on determined that most recent common ancestor began diversification 3.46 million years ago [mya; 95 % high probability density (HPD): 1.87-5.71 mya], Central Asia China clade ca. 2.68 mya (95 HPD: 1.28-4.59 mya). expect future studies employing next generation sequencing methods, such RAD-seq, coupled denser inter- intra- specific taxonomic sampling, may prove be cost-effective methods further investigation evolutionary history this