Подсолнечник

Helianthus annuus L.

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Domestication? Competing Theories

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

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

Problems with Mexican Hypothesis (Smith 2006) From Smith 2006

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

Genetic Data (Harter et al 2004) Defined two population clusters (groups with distinct allelle frequencies—18 microsatellite loci –Mexico + Arizona –Central US 10 runs of algorithm assigned domesticates to US After subdividing US cluster, all domesticates assigned to easternmost populations

from Harter et al 2004

Questions Algorithm? Site 20 (Oklahoma)

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

Liu and Burke (2006) cont.

Something I wish had been addressed from Harter et al 2004

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)

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

Literature Cited Crites, G.D Domesticated sunflower in fifth millennium B.P. Temporal Context: New evidence from Middle Tennessee. American Antiquity, 58: Harter, A.V., K.A. Gardner, D. Falush, D.L. Lentz, R.A. Bye, L.H. Rieseberg Origin of extant domesticated sunflowers in eastern North America. Nature, 430: 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: 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.) Darwin’s Harvest: New Approaches to the Origins, Evolution, and Conservation of Crops. Columbia University Press. Smith, B.D Eastern North America as an independent center of plant domestication. Proceedings of the National Academy of Sciences, U.S.A. 103: Snow, A.A., P. Moran-Palma, L.H. Rieseberg, A. Wszelaki, G.J. Seiler Fecundity, phenology, and seed dormancy of F1 Wild-Crop Hybrids in Sunflower (Helianthus annuus, Asteraceae). American Journal of Botany, 85: Snow, A.A., D. Pilson, L.H. Rieseberg, M.J. Paulsen, N. Pleskac, M.R. Reagon, D.E. Wolf, S.M. Selbo A Bt transgene reduced herbivory and enhances fecundity in wild sunflowers. Ecological Applications, 13: Wills, D.M., J.M. Burke Chloroplast DNA variation confirms a single origin of domesticated sunflower (Helianthus annuus L.). Journal of Heredity, 97: