title: Morphological variation in leaf dissection of Rheum palmatum complex (Polygonaceae).
abstract: OBJECTIVE
  Rheum palmatum complex comprises all taxa within section Palmata in the genus Rheum, including R. officinale, R. palmatum, R. tanguticum, R. tanguticum var. liupanshanense and R. laciniatum. The identification of the taxa in section Palmata is based primarily on the degree of leaf blade dissection and the shape of the lobes; however, difficulties in species identification may arise from their significant variation. The aim of this study is to analyze the patterns of variation in leaf blade characteristics within and among populations through population-based sampling covering the entire distribution range of R. palmatum complex.
  
  
  METHODS
  Samples were taken from 2340 leaves from 780 individuals and 44 populations representing the four species, and the degree of leaf blade dissection and the shape of the lobe were measured to yield a set of quantitative data. Furthermore, those data were statistically analyzed.
  
  
  RESULTS
  The statistical analysis showed that the degree of leaf blade dissection is continuous from lobed to parted, and the shape of the lobe is also continuous from broadly triangular to lanceolate both within and between populations. We suggested that taxa in section Palmata should be considered as one species. Based on the research on the R. palmatum complex, we considered that the quantitative characteristics were greatly influenced by the environment. Therefore, it is not reliable to delimitate the species according to the continuously quantitative vegetative characteristics.
authors.affiliation: School of Pharmacy, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Xu-Mei
authors.initials: XM
authors.lastname: Wang
authors.affiliation: Guiyang Museum of Medical Resources, Guiyang Botanical Garden of Medicinal Plants, Guiyang, China.
authors.forename: Xiao-Qi
authors.initials: XQ
authors.lastname: Hou
authors.affiliation: College of Life Sciences, Shaanxi Normal University, Xi'an, China.
authors.forename: Yu-Qu
authors.initials: YQ
authors.lastname: Zhang
authors.affiliation: School of Pharmacy, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
mesh_terms: D004777:Environment; D005843:Geography; D010641:Phenotype; D018515:Plant Leaves / Q000033:anatomy & histology*; D012250:Rheum / Q000033:anatomy & histology*