196W Poster - Population Genetics
Wednesday June 08, 8:30 PM - 9:15 PM

Authors:
Nathan Wales ^1,2; Melis Akman ^1,3; Peter Stokes ¹; Ray Watson ^1,4; Greg Owens ^1,5; Bruce Smith ⁶; Kristen Gremillion ⁷; M. Thomas Gilbert ⁸; Benjamin Blackman ¹

Affiliations:
1) University of California, Berkeley; 2) University of York; 3) California State University, East Bay; 4) University of Virginia; 5) University of Victoria; 6) Smithsonian Institution; 7) Ohio State University; 8) University of Copenhagen

Keywords:
Ancient DNA

Where and how many times crop plants were domesticated, how strong and how quickly genetic diversity is lost during domestication, and how domestication syndromes are assembled through polygenetic evolutionary change are questions of active research and frequent debate. We have been addressing these questions with archaeological DNA approaches in the common sunflower, Helianthus annuus. Native American farmers living ~4000-5000 years ago transformed the common sunflower from a highly branched wild plant with small disks and small seeds into a staple oilseed crop that sports a single large head with large seeds on an unbranched stalk. We have assembled a time series of archaeological samples that spans the majority of this period, and we are using endogenous DNA sequences obtained from these samples to reveal how human cultivation altered genetic diversity through time. My talk will focus on how the genomic libraries obtained from these samples and from ethnographic collections from the historic period are proving fruitful for examining hypotheses about where in North America sunflower was domesticated and for highlighting reductions in sequence diversity at multiple time points in the history of sunflower cultivation. The intriguing patterns of haplotype turnover we observe through time also suggest that shifts in agricultural practices have occurred over this period. In addition, my talk will discuss how we have defined a set of candidate domestication genes through population genomics and transcriptomics approaches with extant germplasm, and how targeted resequencing of these loci from our archaeological times series has revealed the timing and order of selective sweeps and thus insight into how the sunflower domestication syndrome was assembled by Native American farmers through time.