title: Phylogenetics of the Chamaesyce clade (Euphorbia, Euphorbiaceae): reticulate evolution and long-distance dispersal in a prominent C4 lineage.
abstract: OBJECTIVE
  The Chamaesyce clade of Euphorbia is the largest lineage of C(4) plants among the eudicots, with 350 species including both narrow endemics and cosmopolitan weeds. We sampled this group worldwide to address questions about subclade relationships, the origin of C(4) photosynthesis, the evolution of weeds, and the role of hybridization and long-distance dispersal in the diversification of the group. •
  
  
  METHODS
  Two nuclear (ITS and exon 9 of EMB2765) and three chloroplast markers (matK, rpl16, and trnL-F) were sequenced for 138 ingroup and six outgroup species. Exon 9 of EMB2765 was cloned in accessions with >1% superimposed peaks. •
  
  
  RESULTS
  The Chamaesyce clade is monophyletic and consists of three major subclades [1(2,3)]: (1) the Acuta clade, containing three North American species with C(3) photosynthesis and C(3)-C(4) intermediates; (2) the Peplis clade, mostly North American and entirely C(4); and (3) the Hypericifolia clade, all C(4), with both New World and Old World groups. Incongruence between chloroplast and ITS phylogenies and divergent cloned copies of EMB2765 exon 9 suggest extensive hybridization, especially in the Hawaiian Islands radiation. •
  
  
  CONCLUSIONS
  The Chamaesyce clade originated in warm, arid areas of North America, where it evolved C(4) photosynthesis. From there, it diversified globally with extensive reticulate evolution and frequent long-distance dispersals. Although many species are weedy, there are numerous local adaptations to specific substrates and regional or island radiations, which have contributed to the great diversity of this group.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, 830 North University Avenue, Ann Arbor, Michigan 48109-1048 USA. yangya@umich.edu
authors.forename: Ya
authors.initials: Y
authors.lastname: Yang
authors.forename: Paul E
authors.initials: PE
authors.lastname: Berry
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D018744:DNA, Plant / Q000235:genetics; D028481:Euphorbia / Q000145:classification / Q000235:genetics*; D019143:Evolution, Molecular; D005091:Exons; D017343:Genes, Plant; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid
chemical_list: D017931:DNA Primers; D018744:DNA, Plant