Helianthus%20annuus%20L.

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Helianthus annuus L.
http//www.uapress.arizona.edu/onlinebks/weeds/sun
flowr.htm
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http//www.artquotes.net/masters/vangogh/vangogh_s
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http//www.1st-art-gallery.com/artists/vincent_van
_gogh/van_goghs1.jpg
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http//www.art.com/asp/sp-asp/_/pd--10106228/sp--A
/Sunflowers.htm
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Domestication? Competing Theories
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Mexican Hypothesis (Lentz et al 2001)

• Archaeological evidence
• San Andrés, Tabasco, Mexico
• Dated to 4130 40 B.P. (seed) and 4085 50 B.P.
  (achene)
• Size well within range of domesticated sunflower
  seeds

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Eastern North American Hypothesis (Crites 1993)

• Archaeological evidence
• 6 completely carbonized sunflower seeds
• 4265 60 years B.P.
• Hayes site, Tennessee, U.S.A.
• Size (length increased by 30, width by 45)
• 5.7 mm x 2.2 mm
• 7.3 mm x 3.3 mm
• 6.7 mm x 2.9 mm
• 6.9 mm x 2.9 mm
• 7.3 mm x 2.9 mm
• 7.4 mm x 3.8 mm

cutoff for domestication is between 5 and 7 mm
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Problems with Mexican Hypothesis (Smith 2006)
From Smith 2006
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Problems with Mexican Hypothesis (Smith 2006)

• No documentation that San Andrés seed is
  Helianthus annuus.
• San Andrés achene lacks striations indicative of
  H. annuus.
• San Andrés is outside of current wild range

From Smith 2006
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Genetic Data (Harter et al 2004)

• Defined two population clusters (groups with
  distinct allelle frequencies18 microsatellite
  loci
• Mexico Arizona
• Central US
• 10 runs of algorithm assigned domesticates to US
• After subdividing US cluster, all domesticates
  assigned to easternmost populations

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from Harter et al 2004
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from Harter et al 2004
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from Harter et al 2004
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Questions

• Algorithm?
• Site 20 (Oklahoma)

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More genetic data

• Wills and Burke (2006)
• chloroplast DNA suggests (?) single origin of
  domesticated sunflower in U.S.
• Liu and Burke (2006)
• nucleotide diversity confirms single origin of
  domesticated sunflower
• cannot determine location of event

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Liu and Burke (2006) cont.
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Something I wish had been addressed
from Harter et al 2004
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• Liu and Burke (2006) only published a phylogeny
  including Native American land races.
• Gene flow is easy (Snow et al 1998 and cited
  refs.) and it affects the behavior of wild plants
  (Snow et al 2003)

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• How should one deal with gene flow between crops
  and wild relatives?
• At what point will gene flow obscure any
  phylogenetic signal?

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Literature Cited

• Crites, G.D. 1993. Domesticated sunflower in
  fifth millennium B.P. Temporal Context New
  evidence from Middle Tennessee. American
  Antiquity, 58 146-148.
• Harter, A.V., K.A. Gardner, D. Falush, D.L.
  Lentz, R.A. Bye, L.H. Rieseberg. 2004. Origin
  of extant domesticated sunflowers in eastern
  North America. Nature, 430 201-205.
• Lentz, D.L. M.E.D. Pohl, K.O. Pope, A.R. Wyatt.
  (2001). Prehistoric Sunflower (Helianthus annuus
  L.) Domestication in Mexico. Economic Botany,
  55 370-376.
• Rieseberg, L.H., A.V. Harter. (2006). Molecular
  evidence and the evolutionary history of the
  domesticated sunflower. In Motley, T. N. Zerega,
  H. Cross (eds.) Darwins Harvest New Approaches
  to the Origins, Evolution, and Conservation of
  Crops. Columbia University Press.
• Smith, B.D. 2006. Eastern North America as an
  independent center of plant domestication.
  Proceedings of the National Academy of Sciences,
  U.S.A. 103 12223-12228.
• Snow, A.A., P. Moran-Palma, L.H. Rieseberg, A.
  Wszelaki, G.J. Seiler. 1998. Fecundity,
  phenology, and seed dormancy of F1 Wild-Crop
  Hybrids in Sunflower (Helianthus annuus,
  Asteraceae). American Journal of Botany, 85
  794-801.
• Snow, A.A., D. Pilson, L.H. Rieseberg, M.J.
  Paulsen, N. Pleskac, M.R. Reagon, D.E. Wolf, S.M.
  Selbo. 2003. A Bt transgene reduced herbivory
  and enhances fecundity in wild sunflowers.
  Ecological Applications, 13 279-286.
• Wills, D.M., J.M. Burke. 2006. Chloroplast DNA
  variation confirms a single origin of
  domesticated sunflower (Helianthus annuus L.).
  Journal of Heredity, 97 403-408.