title: Phylogeny, character evolution, and biogeography of Cuscuta (dodders; Convolvulaceae) inferred from coding plastid and nuclear sequences.
abstract: OBJECTIVE
  The parasitic genus Cuscuta, containing some 200 species circumscribed traditionally in three subgenera, is nearly cosmopolitan, occurring in a wide range of habitats and hosts. Previous molecular studies, on subgenera Grammica and Cuscuta, delimited major clades within these groups. However, the sequences used were unalignable among subgenera, preventing the phylogenetic comparison across the genus.
  
  
  METHODS
  We conducted a broad phylogenetic study using rbcL and nrLSU sequences covering the morphological, physiological, and geographical diversity of Cuscuta. We used parsimony methods to reconstruct ancestral states for taxonomically important characters. Biogeographical inferences were obtained using statistical and Bayesian approaches.
  
  
  RESULTS
  Four well-supported major clades are resolved. Two of them correspond to subgenera Monogynella and Grammica. Subgenus Cuscuta is paraphyletic, with section Pachystigma sister to subgenus Grammica. Previously described cases of strongly supported discordance between plastid and nuclear phylogenies, interpreted as reticulation events, are confirmed here and three new cases are detected. Dehiscent fruits and globose stigmas are inferred as ancestral character states, whereas the ancestral style number is ambiguous. Biogeographical reconstructions suggest an Old World origin for the genus and subsequent spread to the Americas as a consequence of one long-distance dispersal.
  
  
  CONCLUSIONS
  Hybridization may play an important yet underestimated role in the evolution of Cuscuta. Our results disagree with scenarios of evolution (polarity) previously proposed for several taxonomically important morphological characters, and with their usage and significance. While several cases of long-distance dispersal are inferred, vicariance or dispersal to adjacent areas emerges as the dominant biogeographical pattern.
authors.affiliation: Department of Biology, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: García
authors.forename: Mihai
authors.initials: M
authors.lastname: Costea
authors.forename: Maria
authors.initials: M
authors.lastname: Kuzmina
authors.forename: Saša
authors.initials: S
authors.lastname: Stefanović
mesh_terms: D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D034182:Cuscuta / Q000235:genetics*; D058893:DNA Barcoding, Taxonomic; D018744:DNA, Plant / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics*; D005843:Geography; D008969:Molecular Sequence Data; D010802:Phylogeny; D018087:Plastids / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D018744:DNA, Plant; D004275:DNA, Ribosomal; C101625:RbcL protein, plastid; D012273:Ribulose-Bisphosphate Carboxylase
keywords: Convolvulaceae; Cuscuta; character evolution; molecular phylogeny; nrLSU; parasitic plants; rbcL; reticulate evolution