Domesticating Chenopodium: applying genetic techniques and archaeological data to understanding pre-contact plant use in southern Manitoba (AD1000-1500).
Date
2017
Authors
Halwas, Sara
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Abstract
Current understanding of pre-contact subsistence economies in southern Manitoba indicates hunter-harvester cultural groups were consuming and potentially cultivating domesticated plants (e.g. maize and beans). These may have originated through long distance trade and/or migration stemming from the adjacent Eastern Woodlands region in eastern North America. Within the Eastern Woodlands, native species (e.g. Chenopodium berlandieri) were domesticated for their seed ca. 3500BP. This raises the possibility that cultural groups in southern Manitoba may also have cultivated local native plant species.
This interdisciplinary research explored the potential effects of cultivation on plant and seed traits of C. berlandieri. Data were collected to reassess archaeobotanical seed remains from the Lockport (EaLf-1) and Forks (DlLg-33:08A) archaeological sites in southern Manitoba to gain a better understanding of pre-contact subsistence strategies.
Ten wild C. berlandieri populations surveyed from southern Manitoba to Ohio revealed that populations within each region produced a wide range of plant and seed phenotypes, including varied seed production. Compared to plant phenotypes from parental populations, wild Manitoba seed grown in a cultivated environment increased in total plant size, seed production and exhibited larger seeds with thinner testas. Similarly, percent germination increased for seed produced in a cultivated setting. Seed size and testa thickness were highly heritable and strongly inversely correlated indicating a firm genetic basis for variation in seed traits. Thus low-level cultivation practices created conditions that would have promoted the evolution of the domesticated phenotype (i.e. large seeds with very thin testas).
Archaeological C. berlandieri specimens recovered from the Lockport and Forks sites exhibited testa thicknesses nearer the ‘thin’ end of the natural range of variation (0.025-0.035mm) for wild populations in Manitoba. This range of variation in seed traits appears to match ‘weedy’ populations associated with domesticated goosefoot crops from Eastern Woodland sites. ‘Weedy’ populations exposed to cultivated environments apparently developed intermediate seed phenotypes. In Manitoba, archaeological C. berlandieri seeds that exhibit relatively thin testas may indicate an intermediate ‘cultivated phenotype’ between wild and domesticated seed morphologies.
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Keywords
Chenopodium berlandieri, Seed traits, Cultivation, Process of domestication, Phenotypic variation, Genetic variation, Manitoba archaeobotany, Subsistence strategies