Résumé
The action of biological, environmental and social factors on crop evolutionary processes call for an interdisciplinary approach that combine biological and social sciences to get a comprehensive interpretation of crop diversity patterns. At different scales and for different species, several studies have shown that the organization of neutral crop genetic diversity may be associated to farmers' social organization. However, the observed patterns may result from very diverse sociocultural and biological processes, often historically linked, imposing a case-by-case interpretation. Here we compare studies conducted on sorghum in a contact zone of several sociocultural groups in Mount Kenya with a larger scale studies on pearl millet and Bambara groundnut in the Lake Chad Basin. The organization of crop genetic diversity is linked to farmers' social organization in the case of sorghum on Mount Kenya and of pearl millet at the west side of Lake Tchad, but not in the case of Bambara groundnut. The genetic diversity of crops was also structured by varieties attributes (phenological cycle duration, uses, and status - introduced or local). The uneven distribution of crop genetic clusters among sociocultural groups shows that population genetics methods can be used as innovative approaches by social scientists to interpret historical, sociocultural, and economic processes that may have influenced the organization of the genetic diversity of these crops. Crop diversity dynamics can be better understood by taking precisely into account current farmer's knowledge and practices about seed circulation, selection, and varieties choices, documented with an historical background. A better representation of how social and biological factors have interacted, over time and across different environments, to shape the crop diversity and to preserve its adaptability should help to advocate for a legal and political recognition of farmers' knowledge and practices in dynamic management of crop diversity.