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Abstract:
People introduced maize (Zea mays ssp. mays) to the southwestern US by 4,000 years ago. Full maize agriculture was established quickly in the lowland deserts but delayed in the temperate uplands for 2,000 years. Here, we hypothesized that this delay was caused by the necessity to select for early flowering, a characteristic of agriculturally important modern temperate maize. We sequenced fifteen 1,900-year old maize cobs from Turkey Pen Shelter in the temperate Southwest (contemporary Utah, USA). Genomic prediction models trained on diverse inbred lines and validated in modern landraces predicted that Turkey Pen maize was early flowering and therefore marginally adapted to its local environment. Population genetic analyses suggested temperate adaptation drove modern population differentiation and adaptive alleles were selected in situ from ancient standing variation. We showed that validated prediction of polygenic traits in crops improves our understanding of ancient phenotypes and opens up new avenue towards understanding our history and those of the animals and plants we domesticated.
