title: Diversification of the American bulb-bearing Oxalis (Oxalidaceae): dispersal to North America and modification of the tristylous breeding system.
abstract: OBJECTIVE
  The American bulb-bearing Oxalis (Oxalidaceae) have diverse heterostylous breeding systems and are distributed in mountainous areas from Patagonia to the northeastern United States. To study the evolutionary processes leading to this diversity, we constructed the first molecular phylogeny for the American bulb-bearing Oxalis and used it to infer biogeographic history and breeding system evolution.
  
  
  METHODS
  We used DNA sequence data (nuclear ribosomal internal transcribed spacer, trnL-trnL-trnF, trnT-trnL, and psbJ-petA) to infer phylogenetic history via parsimony, likelihood, and Bayesian analyses. We used Bayes Multistate to infer ancestral geographic distributions at well-supported nodes of the phylogeny. The Shimodaira-Hasegawa (SH) test distinguished among hypotheses of single or multiple transitions from South America to North America, and tristyly to distyly.
  
  
  RESULTS
  The American bulb-bearing Oxalis include sampled members of sections Ionoxalis and Pseudobulbosae and are derived from a larger clade that includes members of sections Palmatifoliae, Articulatae, and the African species. The American bulb-bearing Oxalis comprise two clades: one distributed in SE South America and the other in the Andes and North America. An SH test supports multiple dispersals to North America. Most sampled distylous species form a single clade, but at least two other independent distylous lineages are supported by the topologies and SH tests.
  
  
  CONCLUSIONS
  Phylogenetic results suggest the American bulb-bearing Oxalis originated in southern South America, dispersed repeatedly to North America, and had multiple transitions from tristyly to distyly. This study adds to our understanding of biogeographic history and breeding system evolution and provides a foundation for more precise inferences about the study group.
authors.affiliation: Department of Botany, University of Wisconsin-Madison, 53706, USA. aggardner@wisc.edu
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Gardner
authors.forename: Magdalena
authors.initials: M
authors.lastname: Vaio
authors.forename: Marcelo
authors.initials: M
authors.lastname: Guerra
authors.forename: Eve
authors.initials: E
authors.lastname: Emshwiller
mesh_terms: D001483:Base Sequence; D001499:Bayes Theorem; D005075:Biological Evolution; D001947:Breeding; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D035264:Flowers / Q000235:genetics; D005843:Geography; D019684:Magnoliopsida / Q000235:genetics*; D008969:Molecular Sequence Data; D009656:North America; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D018744:DNA, Plant; D021903:DNA, Ribosomal Spacer