This study will trace genetic changes over a 3000 year period to understand the evolution of domestication in sunflower. Understanding how the complex suites of traits associated with domestication are assembled over time is a central but empirically challenging question in evolutionary biology and a topic of critical importance to agriculture, conservation, and human health. Adaptations frequently involve the coordinated change of multiple morphological, physiological, or behavioral characters, and this pattern is especially true with respect to the transformation of wild plants into crops. Domesticated approximately 5000 years ago by Native Americans, this important staple crop has a rich archaeological record and extensive genomic resources. Using cutting-edge DNA sequencing methods, a dataset reflecting the time series covering the domestication period from ancient through contemporary DNA will be developed. The research can provide new perspectives on agriculture and trade by early Native American cultures. Trainees gain international experience at the Centre for GeoGenetics in Copenhagen. A high school genomics curriculum will be developed through a summer internship program at the National Museum of Natural History that directly engages high school students in scientific discovery through initial sequencing of a new plant genome.
Genome-wide studies of ancient DNA have been made possible by recent technological advances and provide a unique opportunity to reconstruct the historical genetic sequence of multi-trait adaptation. By following the timing and order with which beneficial genetic changes, and by inference changes in domestication traits, accumulate, the DNA dataset obtained will address a core debate over how fast domestication proceeded and test key predictions from evolutionary theory. Several hundred candidate domestication genes identified through genomic diversity and gene expression studies will be followed over an archaeological time series covering the domestication period. Using cutting-edge solution-based sequence capture methods to vastly enrich recovery of specific sequences, several hundred of these genes will be genotyped over a time series using sunflower archaeological remains covering the domestication period. By combining this genotypic information with knowledge of gene function, the project will determine which traits evolved earlier during domestication than others and whether those traits share common features. Through integrating the ancient DNA data with existing data on effect sizes, the project will test whether variants associated with large differences in phenotype predominantly appear early or late in the adaptation process. Sunflower is an important crop today, is divergent from its wild relative in many traits, and this genetic study provides a unique opportunity to investigate how and under what conditions different evolutionary forces and genetic phenomena influence the timing and order of beneficial substitutions affecting an integrated set of traits
