Data from: Unexpected pattern of pearl millet genetic diversity among ethno-linguistic groups in the Lake Chad Basin

Despite of a growing interest for considering the role of sociological factors in seed exchanges and their consequences on the evolutionary dynamics of agro-biodiversity, very few studies assessed the link between ethno-linguistic diversity and genetic diversity patterns in smallholder farming systems. This is a key for optimal improvement and conservation of crop genetic resources.Here, we investigated genetic diversity at 17 SSR markers of pearl millet landraces in the Lake Chad Basin. 69 pearl millet populations, representing 27 landraces collected in eight ethno-linguistic farmer groups, were analyzed. We found that the farmers’ local taxonomy was not a good proxy for population’s genetic differentiation as previously shown at smaller scales. Our results show the existence of a genetic structure of pearl millet mainly associated with ethno-linguistic diversity in the western side of the lake Chad. It suggests there is a limit to gene flow between landraces grown by different ethno-linguistic groups. This result was rather unexpected, because of the highly outcrossing mating system of pearl millet, the high density of pearl millet fields all along the green belt of this Sahelian area and the fact that seed exchanges among ethno-linguistic groups are known to occur. In the eastern side of the Lake, the pattern of genetic diversity suggests a larger efficient circulation of pearl millet genes between ethno-linguistic groups which are less numerous, spatially intermixed and, for some of them, more prone to exogamy. Finally, other historical and environmental factors which may contribute to the observed diversity patterns are discussed.尽管学界日益关注社会因素在种子交换中的作用，及其对农业生物多样性演化动态的影响，但目前极少有研究探讨小农农业系统中民族语言多样性与遗传多样性模式之间的关联。这对于作物遗传资源的优化改良与保护至关重要。本研究针对乍得湖盆地的珍珠粟（pearl millet）地方品种，基于17个简单序列重复（SSR, Simple Sequence Repeat）标记分析其遗传多样性。我们共分析了69个珍珠粟种群，这些种群对应于从8个农民民族语言群体中收集的27个地方品种。研究发现，农民的本土分类体系并不能像小规模研究中那样，很好地反映种群的遗传分化情况。本研究结果显示，乍得湖西侧的珍珠粟遗传结构主要与民族语言多样性相关，这表明不同民族语言群体种植的地方品种之间存在基因流限制。这一结果颇出人意料，因为珍珠粟属于高度异交的交配体系，该萨赫勒地区的绿色带沿线珍珠粟种植密度极高，且已知不同民族语言群体之间存在种子交换行为。而在乍得湖东侧，遗传多样性模式则显示，民族语言群体间的珍珠粟基因流通更为高效——这些群体数量更少、空间上相互交错，且部分群体更倾向于族外婚。最后，本文还探讨了可能影响观测到的多样性模式的其他历史与环境因素。