Turning Over a New Leaf: Experimental Investigations into the Role of Developmental Plasticity in the Domestication of Goosefoot (Chenopodium berlandieri) in Eastern North America

In eastern North America, Indigenous peoples domesticated several crops that are now extinct. We present experimental data that alters our understanding of the domestication of one of these—goosefoot (Chenopodium berlandieri). Ancient domesticated goosefoot has been recognized on the basis of seed morphology, especially a decrease in the thickness of the seed coat (testa). Nondomesticated goosefoot also sometimes produces seeds that look similar or even identical to domesticated ones, but researchers believed that such seeds were rare (1%–3%). We conducted a common garden experiment and a series of carbonization experiments to better understand the determinants of seed polymorphism in archaeobotanical assemblages. We found that goosefoot produces much higher percentages of thin-testa seeds (mean 50% in our experiment, 15%–34% in free-living parent populations) than previously reported. We also found that cultivated plants produce more thin-testa seeds than their free-living parents, demonstrating that this trait is plastic in response to a garden environment. The carbonization experiments suggest that thin-testa seeds preserve under a larger window of conditions than thick-testa seeds, contrary to our expectations. These results suggest that (1) carbonized, phenotypically mixed assemblages should be interpreted cautiously, and (2) developmental plasticity and genetic assimilation played a role in the domestication of goosefoot.