title: Gene flow and genetic diversity in cultivated and wild cacao (Theobroma cacao) in Bolivia.
abstract: OBJECTIVE
  The role of pollen flow within and between cultivated and wild tropical crop species is little known. To study the pollen flow of cacao, we estimated the degree of self-pollination and pollen dispersal distances as well as gene flow between wild and cultivated cacao (Theobroma cacao L.).
  
  
  METHODS
  We studied pollen flow and genetic diversity of cultivated and wild cacao populations by genotyping 143 wild and 86 cultivated mature plants and 374 seedlings raised from 19 wild and 25 cultivated trees at nine microsatellite loci.
  
  
  RESULTS
  A principal component analysis distinguished wild and cultivated cacao trees, supporting the notion that Bolivia harbors truly wild cacao populations. Cultivated cacao had a higher level of genetic diversity than wild cacao, presumably reflecting the varied origin of cultivated plants. Both cacao types had high outcrossing rates, but the paternity analysis revealed 7-14% self-pollination in wild and cultivated cacao. Despite the tiny size of the pollinators, pollen was transported distances up to 3 km; wild cacao showed longer distances (mean = 922 m) than cultivated cacao (826 m). Our data revealed that 16-20% of pollination events occurred between cultivated and wild populations.
  
  
  CONCLUSIONS
  We found evidence of self-pollination in both wild and cultivated cacao. Pollination distances are larger than those typically reported in tropical understory tree species. The relatively high pollen exchange from cultivated to wild cacao compromises genetic identity of wild populations, calling for the protection of extensive natural forest tracts to protect wild cacao in Bolivia.
authors.affiliation: Agroecology, Department of Crop Sciences, Georg August University Göttingen, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Chumacero de Schawe
authors.forename: Walter
authors.initials: W
authors.lastname: Durka
authors.forename: Teja
authors.initials: T
authors.lastname: Tscharntke
authors.forename: Isabell
authors.initials: I
authors.lastname: Hensen
authors.forename: Michael
authors.initials: M
authors.lastname: Kessler
mesh_terms: D001838:Bolivia; D002099:Cacao / Q000235:genetics / Q000502:physiology*; D051456:Gene Flow; D014644:Genetic Variation; D018895:Microsatellite Repeats; D054817:Pollination; D025341:Principal Component Analysis; D014197:Trees / Q000235:genetics / Q000502:physiology; D014329:Tropical Climate
keywords: microsatellites; paternity analysis; pollen dispersal; selfing