archaeogenetic evidence of ancient nubian barley evolution from six to two-row indicates local adaptationarchaeogenetic古努比亚从六棱大麦进化的证据表明当地的适应.pdf

Archaeogenetic Evidence of Ancient Nubian Barley Evolution from Six to Two-Row Indicates Local Adaptation 1 1 2 3 1 Sarah A. Palmer , Jonathan D. Moore , Alan J. Clapham , Pamela Rose , Robin G. Allaby * 1 Warwick HRI, The University of Warwick, Wellesbourne, United Kingdom, 2 Worcestershire Historic Environment Archaeology Service, Woodbury, University of Worcester, Worcester, United Kingdom, 3 The McDonald Institute for Archaeological Research, University of Cambridge, Cambridge, United Kingdom Abstract Background: Archaeobotanical samples of barley (Hordeum vulgare L.) found at Qasr Ibrim display a two-row phenotype that is unique to the region of archaeological sites upriver of the first cataract of the Nile, characterised by the development of distinctive lateral bracts. The phenotype occurs throughout all strata at Qasr Ibrim, which range in age from 3000 to a few hundred years. Methodology and Findings: We extracted ancient DNA from barley samples from the entire range of occupancy of the site, and studied the Vrs1 gene responsible for row number in extant barley. Surprisingly, we found a discord between the genotype and phenotype in all samples; all the barley had a genotype consistent with the six-row condition. These results indicate a six-row ancestry for the Qasr Ibrim barley, followed by a reassertion of the two-row condition. Modelling demonstrates that this sequence of evolutionary events requires a strong selection pressure. Conclusions: The two-row phenotype at Qasr Ibrim is caused by a different mechanism to that in extant barley. The strength of selection required for this mechanism to prevail indicates that the barley became locally adapted in the region in