1. Department of Biology, Indiana University, Bloomington, Indiana 47405, USA
2. Peter Medawar Building for Pathogen Research, University of Oxford, South Parks Road, Oxford OX1 3SY, UK
3. Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, Illinois 60022, USA
4. Jardín Botánico Exterior, Instituto de Biología, UNAM, México DF 04510, México

Correspondence to: Abigail V. Harter¹ Email: avharter@bio.indiana.edu

Abstract

Eastern North America is one of at least six regions of the world where agriculture is thought to have arisen wholly independently^{1, 2, 3, 4, 5}. The primary evidence for this hypothesis derives from morphological changes in the archaeobotanical record of three important crops—squash, goosefoot and sunflower—as well as an extinct minor cultigen, sumpweed^{1, 3}. However, the geographical origins of two of the three primary domesticates—squash and goosefoot—are now debated^{6, 7}, and until recently sunflower (Helianthus annuus L.) has been considered the only undisputed eastern North American domesticate. The discovery of 4,000-year-old domesticated sunflower remains from San Andrés, Tabasco^{8, 9}, implies an earlier and possibly independent origin of domestication in Mexico and has stimulated a re-examination of the geographical origin of domesticated sunflower. Here we describe the genetic relationships and pattern of genetic drift between extant domesticated strains and wild populations collected from throughout the USA and Mexico. We show that extant domesticates arose in eastern North America, with a substantial genetic bottleneck¹⁰ occurring during domestication.

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