Marriage exchanges, seed exchanges, and the dynamics of manioc diversity

Abstract

The conservation of crop genetic resources requires understanding the different variables-cultural, social, and economic-that impinge on crop diversity. In small-scale farming systems, seed exchanges represent a key mechanism in the dynamics of crop genetic diversity, and analyzing the rules that structure social networks of seed exchange between farmer communities can help decipher patterns of crop genetic diversity. Using a combination of ethnobotanical and molecular genetic approaches, we investigated the relationships between regional patterns of manioc genetic diversity in Gabon and local networks of seed exchange. Spatially explicit Bayesian clustering methods showed that geographical discontinuities of manioc genetic diversity mirror major ethnolinguistic boundaries, with a southern matrilineal domain characterized by high levels of varietal diversity and a northern patrilineal domain characterized by low varietal diversity. Borrowing concepts from anthropology-kinship, bridewealth, and filiation-we analyzed the relationships between marriage exchanges and seed exchange networks in patrilineal and matrilineal societies. We demonstrate that, by defining marriage prohibitions, kinship systems structure social networks of exchange between farmer communities and influence the movement of seeds in metapopulations, shaping crop diversity at local and regional levels.seed transmission | social reproduction | traditional economic systems I n smallholder farming systems, farmers maintain a large diversity of cultivated species and recognize many different types (landraces) within each of their crops. Farmers dynamically manage this agricultural biodiversity by continually collecting, testing, and selecting new strains with unusual and interesting traits, sourcing "seeds" (here understood as propagules, i.e., true seeds, tubers, rhizomes, or stem cuttings) through different networks, most of which involve exchanging germplasm with other farmers.Several studies have highlighted the importance of informal seed exchange networks as an essential component of the resilience of local farming systems (1, 2), e.g., in potato (3), maize (4, 5), and manioc (6-8). Exchanging seeds not only allows farmers to obtain new landraces but also to recover lost types or to renew their stock of seeds (1). Through these exchange networks, farmers compile highly diversified portfolios of landraces capable of buffering the effects of unpredictable environmental changes (2). Seed exchange represents a key mechanism in the dynamics of crop genetic diversity (9-11). However, the rules that channel the movement of seeds within and among farming communities have received little attention from geneticists and ethnobotanists alike (12).In small-scale farming communities, circulation of crop landraces is often channeled by marriage networks (7,8,13,14). By defining marriage prohibitions, kinship systems structure social networks of exchange between kin (related by descent) and affines (related by marriage). Kinship systems thus determine the conn...

Tartary Buckwheat Genetic Diversity in the Himalayas Associated with Farmer Landrace Diversity and Low Dietary Dependence

“…Previous studies have shown that farmers' seed sharing networks drive the gene flow of crops within a region [9,17,18,50]. Access to diverse crop germplasm requires that farmers have adequate income or connections without social or political constraints to acquire different crop varieties [51].…”

“…Neighborhood groups [9] and marriage exchanges are other social factors that shape crop diversity at local and regional levels [16][17][18][19].…”

Genetic diversity, population structure, and traditional culture of Camellia reticulata

“…Previous studies have acknowledged the role of traditional knowledge and culture practices of smallholder farmers and indigenous communities for biodiversity conservation at the species, genetic, ecosystem, and landscape levels (Altieri, 2004). Many traditional management practices, customs, and beliefs have been reported to contribute to biodiversity protection including seed exchange systems (Labeyrie, Thomas, Muthamia, & Leclerc, 2016), marriage exchanges (Delêtre, McKey, & Hodkinson, 2011), religious rituals (Mazumdar & Mazumdar, 2012), and dietary traditions (Penafiel, Lachat, Espinel, Van Damme, & Kolsteren, 2011). These practices, customs, and beliefs have been linked to preserving crop landraces (Jackson, Pascual, & Hodgkin, 2007), old trees (Salick et al., 2007), and economic plants (Liu et al., 2014) including those with esthetic, food, and medicinal values (Begum et al., 2014).…”

Ethnolinguistic structuring of sorghum genetic diversity in Africa and the role of local seed systems

“…operating at finer scales. On-farm management of crop varieties and cultural boundaries influencing the diffusion of seeds, practices, and knowledge are important local-scale explanatory factors behind patterns of regional and continental scale associations between ethnolinguistic groups and crop genetic structure (27)(28)(29)(30).…”