title: Poinsettia's wild ancestor in the Mexican dry tropics: Historical, genetic, and environmental evidence.
abstract: OBJECTIVE
  The poinsettia (Euphorbia pulcherrima) is the world's most economically important potted plant, but despite its preeminence it is not clear which wild populations are ancestral to the varieties cultivated around the world. Tradition holds that the U.S. envoy to Mexico J. R. Poinsett collected the progenitors of the over 300 varieties in global cultivation on an 1828 excursion to northern Guerrero State, Mexico. It is unknown whether the contemporary cultivars are descended from plants from Guerrero or whether germplasm from other parts of poinsettia's 2000 km long distribution entered into cultivation during the nearly 200 yr of subsequent poinsettia horticulture.
  
  
  METHODS
  To identify the wild populations that likely gave rise to the cultivars and test this historical account, we sequenced plastid and nuclear DNA regions and modeled poinsettia's potential distribution.
  
  
  RESULTS
  The combination of nuclear and plastid haplotypes characterizing cultivars was found only in northern Guerrero. Distribution modeling indicated that suitable habitat conditions for wild poinsettias are present in this area, consistent with their likely wild status.
  
  
  CONCLUSIONS
  Our data pinpoint the area of northern Guerrero as the cultivated poinsettia's probable ancestral region, congruent with the traditional account attributing the original collections to Poinsett. Abundant genetic variation likely offers raw material for improving the many shortcomings of cultivars, including vulnerability to cold, stem breakage, and pathogens such as Pythium and Phytophthora. However, genetic differences between populations make conservation of all of poinsettia's diversity difficult.
authors: Instituto de Biología, Universidad Nacional Autónoma de México, México DF, México.
authors: Laura
authors: L
authors: Trejo
authors: Teresa Patricia
authors: TP
authors: Feria Arroyo
authors: Kenneth M
authors: KM
authors: Olsen
authors: Luis E
authors: LE
authors: Eguiarte
authors: Baruch
authors: B
authors: Arroyo
authors: Jennifer A
authors: JA
authors: Gruhn
authors: Mark E
authors: ME
authors: Olson
mesh_terms: D003247:Conservation of Natural Resources; D018744:DNA, Plant / Q000235:genetics; D017753:Ecosystem; D028481:Euphorbia / Q000235:genetics*; D051639:Gardening / Q000266:history*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics; D049672:History, 19th Century; D008800:Mexico; D058974:Phylogeography; D018087:Plastids / Q000235:genetics; D017422:Sequence Analysis, DNA; D014329:Tropical Climate
chemical_list: D018744:DNA, Plant; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases