Traditionally,Atraphaxis,Calligonum,Pteropyrum and Parapteropyrum are included in the tribe Atraphxideae.Recently,sequence data has revealed that this tribe is not monophyletic.The structure of the tribe was examined by adding more taxa and sequences to clarify the congruence between morphology and molecular phylogeny,the systematic placements of four genera in Polygonaceae,as well as the infra-generic relationships of Atraphaxis and Calligonum within Atraphaxideae.Five chloroplast genes,atpB-rbcL,psbA-trnH,trnL–trnF, psbK-psbI,and rbcL of Atraphaxis,Calligonum,Pteropyrum,and Parapteropyrum were sequenced.The non-monophyly of Atraphaxideae was confirmed.Atraphaxis and Calligonum,respectively,formed a monophyletic group that was well supported.Calligonum is closely related to Pteropyrum;Atraphaxis is sister to Polygonum s.str.; and Parapteropyrum is allied with Fagopyrum.Although the morphology suggested the four genera should form a tribe,the molecular data indicated Atraphaxideae was not one monophyletic group.The clades identified within Atraphaxis corresponded well with the current sectional classification based on morphological features.As for Calligonum,Medusa was identified as a non-monophyletic section.
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