title: Biogeography and divergence times of genus Macroptilium (Leguminosae).
abstract: OBJECTIVE
  Macroptilium is a herbaceous legume genus with 18 currently accepted species, seven of them with economic importance due to their use as forage, green fertilizer and in medicine. The genus is strictly American, with an unknown biogeographic history. The aim of this study was to infer a biogeographic pattern of Macroptilium and to estimate its divergence times, using sequences from the nuclear ribosomal DNA internal transcribed spacers.
  
  
  METHODS
  To study the historical biogeography of Macroptilium, two approaches were used: area optimization on a previously obtained phylogeny and a dispersal-vicariance analysis. Divergence times were calculated by Bayesian methods.
  
  
  RESULTS
  The analyses revealed that Macroptilium has its origin in the middle Pliocene, with an estimated age that ranges from 2.9 to 4 million years. The biogeographic analyses placed its origin in South America, specifically on the Chaquean sub-region, where most of the cladogenetic events of the genus took place.
  
  
  CONCLUSIONS
  Macroptilium constitutes a further example of the geographic pattern displayed by numerous Neotropical taxa that moved north from South America to dominate the Central American lowlands after the land connection across the Isthmus of Panama was established.
authors.affiliation: Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales ,  Universidad de Buenos Aires ,  Buenos Aires ,  Argentina.
authors.forename: Shirley M
authors.initials: SM
authors.lastname: Espert
authors.forename: Alicia D
authors.initials: AD
authors.lastname: Burghardt