Le sorgho repiqué a fait l’objet d’une large diffusion dans le bassin du lac Tchad au XXe siècle. Cette culture présente une forte diversité variétale. Les nomenclatures paysannes suggèrent des groupes géographiquement distincts, subdivisés en variétés locales selon des critères qui peuvent varier en fonction des sociétés. À partir d’une taxonomie simplifiée en langue véhiculaire (fulfulde) et de la structure des diversités agro-morphologique et génétique du sorgho repiqué, nous montrons que la variation repose moins sur la définition de catégories taxonomiques intermédiaires (groupes variétaux) que sur celle, plus fine, de taxons terminaux en langues locales (types nommés). Cela est expliqué à l’échelle locale par les pratiques de sélection et de gestion variétale des agriculteurs. La proximité génétique des sorghos repiqués avec certaines populations de sorgho pluvial apporte de nouveaux éléments soutenant les hypothèses sur l’histoire évolutive des sorghos repiqués. L’association du sorgho repiqué à plusieurs clusters génétiques et plusieurs haplotypes chloroplastiques, la circulation régionale relativement récente ainsi que le statut de vivrier marchand du sorgho repiqué ne permettent pas de tracer des frontières géographiques ou culturelles dans la répartition actuelle du sorgho repiqué., A large expansion of dry season sorghum (transplanted sorghum) was noticed in the Lake Chad basin over the last century. A high level of landraces diversity is associated to this crop. We could identify geographical groups of dry season sorghum according to farmers’ nomenclatures; these groups are subdivided into local landraces according to criteria specific to each rural society. Following an ad hoc taxonomy and according to the structure of the agro-morphological variation and genetic diversity of dry season sorghum, we showed that diversity is mainly structured according to the terminal level of the taxonomy (landrace or cultivar). We explained this pattern as the effect of local practices of seed and field management by farmers. Dry season sorghum populations are genetically close to some populations of rainy sorghum; this supports the known hypotheses of dry season sorghum evolutive history. Dry season sorghum belongs to more than a single genetic cluster and exhibited many chloroplastic haplotypes; this is congruent with recent movement of seeds at the regional level and the use of dry season sorghum for both house consumption and markets. This does not allow for the delimitation of geographical and/or cultural boundaries for the use of given landraces of this crop.

Diseases transmitted between wildlife and livestock may have significant impacts on local farmers' health, livestock health and productivity, overall national economies, and conservation initiatives, such as Transfrontier Conservation Areas in Southern Africa. However, little is known on local farmers' awareness of the potential risks, and how they perceive the role played by wildlife in the epidemiology of these diseases. We investigated the knowledge base regarding livestock diseases of local cattle owners living at the periphery of conservation areas within the Great Limpopo TFCA and the Kavango-Zambezi TFCA in Zimbabwe, using free-listing and semi-structured questionnaires during dipping sessions. The results suggest that information related to cattle diseases circulates widely between cattle farmers, including between different socio-cultural groups, using English and vernacular languages. Most respondents had an accurate perception of the epidemiology of diseases affecting their livestock, and their perception of the potential role played by wildlife species was usually in agreement with current state of veterinary knowledge. However, we found significant variations in the cultural importance of livestock diseases between sites, and owners' perceptions were not directly related with the local abundance of wildlife. As the establishment of TFCAs will potentially increase the risk of Transboundary Animal Diseases, we recommend an increased participation of communities at a local level in the prioritisation of livestock diseases control and surveillance, including zoonoses.

In this chapter, we develop new indicators and statistical tests to characterize patterns of crop diversity at local scales to better understand interactions between ecological and socio-cultural functions of agroecosystems. Farms, where a large number of crops (species or landraces) is grown, are known to contribute a large part of the locally available diversity of both rare and common crops but the role of farms with low diversity remains little understood: do they grow only common varieties—following a nestedness pattern typical of mutualistic networks in ecology—or do ‘crop–poor’ farmers also grow rare varieties? This question is pivotal in ongoing efforts to assess the local-scale contribution of small farms to global agrobiodiversity. We develop new network-based approaches to characterize the distribution of local crop diversity (species and infra-species) at the village level and to validate these approaches using meta-datasets from 10 countries. Our results highlight the sources of heterogeneity in crop diversity at the village level. We often identify two or more groups of farms based on their different levels of diversity. In some datasets, ‘crop–poor’ farms significantly contribute to the local crop diversity. Generally, we find that the distribution of crop diversity is more heterogeneous at the species than at the infra-species level. This analysis reveals the absence of a general pattern of crop diversity distribution, suggesting strong dependence on local agro-ecological and socio-cultural contexts. These different patterns of crop diversity distribution reflect an heterogeneity in farmers’ self-organized action in cultivating and maintaining local crop diversity, which ensures the adaptability of agroecosystems to global change.