The conservation of in situ crop diversity is a key issue to ensure food security. Understanding the processes that shape it is crucial for efficiently managing such diversity. In most rural societies, crop diversity patterns are affected by farmers’ practices of seed exchange, transmission, and selection, but the role of social organization in shaping those practices has been overlooked. This study proposes an ecological anthropology approach to investigate the relation between crop diversity patterns and the social organization of Tharaka farmers (...) in Kenya. The Tharaka are organized in neighborhood-groups, clans, and age-sets. We quantified the influence of these three major social institutions on crop diversity patterns, for both crop species and sorghum landraces. General linear models were used to test the relations between crop species richness and each social factor, while the crop species and sorghum landraces compositions of cropping systems were compared separately through a between-class correspondence analysis. Crop species and sorghum landraces are not randomly distributed among farms, and neighborhood-groups constitute a significant factor organizing crop diversity at both specific and infraspecific levels. Adjacent neighborhood-groups present significantly different crop richness and composition. The results for species were consistent with those obtained for sorghum landraces, confirming that crop diversity was socially structured. The influence of social organization on seed networks and selection processes is discussed. (shrink)

Ce travail présente quelques modèles mathématiques de répartition d'objets dans un ensemble de cases devant servir en particulier à l'analyse des résultats expérimentaux concernant la distribution des œufs d'un parasite dans un groupe de ses hôtes. On trouvera successivement une descriptions des situations concrêtes permettant l'utilisation de tels modèles, un rappel sur le matériel d'analyse combinatoire utilisé, cinq modèles relatifs aux différentes hypothèses de distribution au hasard, réception au hasard, reparasitisme à probabilités constante et variable et un exemple d'application aux (...) résultats de V.Labeyrie sur le parasitime d'Acrolepia assectella Z. par un ichneumonide Several mathematical models of distribution of objects among a set of boxes are presented in view of the analysis of experimental results obtained on the distribution of the eggs of a parasite among a group of its hosts.First, practical situations which allow the application of such models are described. In a second part, one recalls the elements of combinatorial analysis required by the following mathematical developments.Five models are then set up, each one being associated with the different hypothesis of: chance distribution, chance acceptance, re-parasitism with constant or variable probability Finally, an exemple of application to the results of V.Labeyrie on the parasitism ofAcrolepia assectella Z. by an ichneumon fly is given.Diese Arbeit soll einige mathematische Modelle von Verteilung der Gegenstände in eine Menge von Fächern geben, deren Zweck im Besonderen die Analyse von Versuchsergebnissen über die Eierlegung eines Parasiten in eine Gruppe seiner Wirte sein will.Es folgen: eine Beschreibung der konkreten Lagen, die eine Verwendung solcher Modelle ermöglichen, eine Aufzählung der benutzten Ergebnisse kombinatorischer Analysis, fünf Modelle, die folgenden verschiedenen Voraüssetzungen entsprechen: Zufallverteilung, Zufallaufnahme, wiederholter Parasitismus mit stetiger oder veränderlicher Wahrscheinlichkeit und ein Anwendungsbeispiel an Ergebnisse von V.Labeyrie über Parasitismus derAcrolepia assectella Z. durch einen Ichneumoniden—. (shrink)