Domestication history of a hexaploid, the sweet potato (Ipomoea batatas (L.) Lam.)

Despite the importance of sweet potato as a food crop, its evolutionary history has been poorly investigated. The geographical and botanical origins of sweet potato remain unclear. Sweet potato is in the section Batatas of the genus, which also includes 13 wild relatives, almost all endemic to the Americas. I. batatas is not known in the wild state. Morphological and genetic analyses indicate that I. trifida is sweet potato¿s closest wild relative, but the genomic composition of I. batatas is still debated. It is still unclear whether this hexaploid is auto-, allo- or auto-allopolyploid. The range of I. trifida extends from northern Peru to Mexico, and the assumed region of origin of I. batatas is somewhere within this vast geographical area. I. trifida forms a complex of ecotypes of differing ploidy levels (diploids to hexaploids), but the distribution and origin of populations of varying ploidy levels are not documented. Morever, no genetic studies have been conducted to determine the relationships between different wild populations of I. trifida and the cultivated I. batatas, which could allow inference of sweet potato¿s region(s) of origin. Finally, a major domesticated trait of I. batatas is its capacity to produce edible storage roots. Some I. trifida are known to form small tuberous roots, but these have not been studied in any depth. The purpose of our study is to investigate the origin of sweet potato and particularly the role of polyploidization in its domestication history. A set of 180 I. trifida populations and 450 sweet potato landraces, distributed from Peru to Mexico, were chosen from the collection of the International Potato Center (CIP, Lima, Peru). Morphological characterisation of these plants is in progress, as well as genetic analyses using neutral chloroplast markers. We plan to evaluate ploidy levels of these different wild and cultivated samples by flow cytometry and study the genome composition of representatives of ploidy groups by genomic in situ hybridization. These analyses should lead to advances in the reconstruction of sweet potato¿s evolutionary history. (Texte intégral

Sorghum, social links and genetic diversity in Northern Cameroon

Sorghum is the Duupa 'cultural supercrop' : it is a main subject of concern for the people and the backbone of the reproduction, on a material and a symbolic way, of the community. More than forty landraces are named and recognized, and widely exchanged between all cultivators in the community. Each year, every cultivator selects panicles from his own previous crop but often mix it with exchanged seeds. Fluxes of seeds follow the lines of kinship or affinal relations, but they can also come from commercial transactions outside the community. An outstanding feature of the Duupa seed system is the institution of free access to sorghum seeds during the collective threshing work parties. Anyone attending these parties can pick a few panicles for his own seeds on the bulk of the crop to be threshed. Strong moral values underline this safety net, which makes the diversity of landraces, seeds a common property. However, these institutionalized exchanged do not account for all the gene flux and people also rely on non-institutionalized, transfers sometimes including grains for current food use rather than properly selectionized panicles. All these transfers, public as well as private, even if difficult to quantify, should be taken into account for a proper understanding of the shaping of sorghum varietal and genetic diversity. (Résumé d'auteur

Des confusions entre espèces préjudiciables à la gestion durable des essences forestières : l'exemple des acajous d'Afrique (Khaya, Meliaceae)

Les espèces du genre Khaya procurent l'un des bois les plus prisés du continent africain. Elles sont commercialisées sous l'appellation " acajou d'Afrique " depuis environ deux siècles. En Afrique continentale, on reconnaît actuellement quatre espèces morphologiquement proches : Khaya anthotheca, K. grandifoliola, K. ivorensis et K. senegalensis. Le nombre de taxons du genre Khaya a varié au cours du temps et la délimitation de ces taxons n'est pas sans avoir des implications sur les stratégies de conservation et de gestion durable des espèces. L'objectif du travail présenté ici est de s'assurer de la délimitation de ces espèces sur la base d'un bilan des connaissances actuelles en taxonomie, génétique, écologie et chimiotaxonomie. Les données disponibles ne permettent pas toujours de séparer sans ambiguïté les quatre acajous d'Afrique continentale. Elles permettent toutefois d'avancer que K. ivorensis, K. grandifoliola et K. senegalensis seraient des espèces à part entière mais dont les limites taxonomiques doivent encore être précisées. Khaya nyasica serait également une espèce qui devrait être séparée de K. anthotheca. Au sein de cette dernière, plusieurs chémotypes ont été identifiés, ce qui suggère que ce taxon pourrait recouvrir un ensemble plus complexe d'au moins deux autres taxons dont le rang spécifique ou sous-spécifique reste à préciser. Des recherches morphométriques, génétiques et écologiques doivent être développées afin de clarifier le statut systématique et l'histoire évolutive de ces divers taxons, en vue de formuler des recommandations appropriées pour la gestion durable des acajous d'Afrique

Variation des caractères biométriques des graines et des plantules de neuf provenances de Tamarindus indica L. (Caesalpinioideae)

Introduction. Tamarindus indica est une espèce fruitière d'intérêt économique. Sa domestication au Sahel impose d'évaluer en préalable la variabilité de ses caractères phénotypiques sur l'ensemble de son aire de répartition. L'objectif de notre étude a été de caractériser différentes provenances de tamarinier à partir des caractères phénotypiques de leurs graines et plantules. Matériel et méthodes. L'étude menée en pépinière au Burkina Faso a porté sur l'étude des graines et germinations issues de neuf provenances dont deux d'Afrique de l'Est, deux d'Afrique de l'Ouest, deux d'Asie et trois de zones insulaires. Nous avons mesuré la longueur, la largeur, l'épaisseur et le poids de 100 graines de chaque provenance, et la hauteur, le diamètre au collet et le poids sec de la tige, ainsi que la longueur de la racine principale, le nombre de racines secondaires et le poids sec du système racinaire de 50 plantules âgées de 3 mois. Nous avons effectué une analyse de variance, puis une analyse en composantes principales sur les données centrées réduites de toutes les variables, enfin une classification hiérarchisée ascendante basée sur des indices de similarité. Résultats et discussion. Les différences entre variables ont été hautement significatives. Lors de l'étude des graines, nous avons obtenu un groupe lié à la provenance d'Inde et d'Afrique de l'Est, un autre lié aux provenances ouest-africaines et un groupe intermédiaire en provenance de Thaïlande. Lors de l'étude des plantules, il est apparu un groupe avec croissance aérienne forte et racine principale courte, fortement ramifiée et un groupe avec croissance aérienne faible, racine principale très longue, mais faiblement ramifiée. Le dendrogramme obtenu à partir des ressemblances phénotypiques (variables des graines et plantules) montre une structuration par aire géographique. Conclusion. La variabilité phénotypique inter provenance des plantules et des graines combinée aux corrélations entre variables pourrait permettre de sélectionner de façon précoce les provenances en fonction des objectifs définis pour la sélection. (Résumé d'auteur

Gestion des ressources génétiques du sorgho (Sorghum bicolor) chez les Duupa (Nord Cameroun)

Le système de diffusion des semences a un impact direct sur la structure génétique des populations de plantes domestiquées et sur son évolution. Ce système peut être caractérisé par ses acteurs, mais aussi par la nature, le sens et l'intensité des échanges. En décrivant les pratiques de sélection et la circulation des semences de sorgho dans la société duupa au Nord Cameroun, notre étude vise à comprendre la dynamique de la diversité génétique. Les agriculteurs duupa maintiennent une importante diversité variétale (40 variétés) qu'ils cultivent en mélange polyvariétal. Chaque année, ils sélectionnent des panicules pour reconduire leur culture, mais peuvent également utiliser des graines non sélectionnées. Les échanges de semences sont importants, et 56 % des agriculteurs se pourvoient auprès de leur famille ou de leurs voisins. Le battage est le moment privilégié des échanges de semences en panicules, mais les agriculteurs duupa introduisent également dans leurs semences des graines à vocation alimentaire échangées à l'occasion de visites et de cérémonies. Les liens sociaux qu'entretiennent les Duupa influencent directement la circulation des semences et sont au coeur de la dynamique de la diversité génétique. (Résumé d'auteur

Reflections on the future of European ethnobiology

In recent years, ethnobiology has undergone significant transformation. A renewed research framework has emerged that prioritizes an ethics of care-one that emphasizes relationships, interdependence, and responsibility towards both human and non-human others throughout all stages of research. This paradigm shift, led largely by Indigenous scholars and researchers from the Global South, invites European ethnobiologists to critically reflect on how they can engage with, contribute to, and learn from these evolving approaches in light of pressing environmental and social challenges. In this Perspective, we explore the future of European ethnobiology in two main ways. First, we reflect on the specificities of a European lens within global ethnobiology, considering how European ethnobiologists might participate more meaningfully in transdisciplinary and intercultural dialogues. Second, drawing on core principles of the emerging global paradigm, we outline five key avenues for future development: (1) deepening commitments to an ethics of care; (2) responding more directly to contemporary challenges; (3) expanding research contexts; (4) reimagining methodological approaches; and (5) enhancing the societal relevance and applied impact of European ethnobiologists, both within and beyond Europe. We highlight current examples of European ethnobiologists already advancing these directions and underscore the field's dynamic evolution. We conclude by identifying critical challenges faced by European ethnobiologists, including the need to engage with rapidly evolving digital technologies and to navigate institutional and epistemic barriers that hinder the co-creation of knowledge across diverse worldviews

Ant-plant symbioses in Africa and the neotropics : history, biogeography and diversity

Book ChapterSymbiotic ant-plant relationships afford an excellent opportunity to analyze the effects of both historical and ecological factors on the evolution of mutualisms. Occurring in tropical forests throughout the world, all myrmecophytic plants provide food and permanent housing to ants; the ants, in turn, are known or presumed to protect their hosts from herbivores or competition or to provision them with nutrients. Despite this underlying similarity, ant-plant symbioses differ in diversity and nature on different landmasses

Altitudinal gradients of tree species diversity and above-ground biomass on a small montane of Atlantic Central Africa

Tropical forests are both important carbon sinks and among the most biodiverse ecosystems on the earth. Patterns in aboveground biomass (AGB) and their relationship with species diversity of tropical forests over short altitudinal gradients are poorly known and the few previous studies on the subject have yielded variable results. Here, focusing on old-growth forests in Atlantic central Africa, we investigated how AGB varies with altitude, and how this variation is related to altitudinal changes in floristic composition and/or forest structure. We also investigate the relationship between AGB and species diversity along the altitudinal gradient. We inventoried all trees with a diameter (dbh) ≥ 10 cm in fifteen 1 ha permanent plots (100 m x 100 m) established along a transect from lowland (200 m) to submontane forests (900 m) in the Ngovayang Massif, southwestern Cameroon. Our data show a negative relationship between AGB and tree species richness, related to the elevation gradient. Forest AGB varied two-fold along this gradient, decreasing from 500-600 Mg ha-1 in lowland plots to less than 300 Mg ha-1 at the highest altitudes, while diversity increased, from 35.4 to 54.6 (Fisher's alpha index). The decreasing trend in AGB was mainly due to large trees (dbh ≥ 70 cm) whose contribution to AGB significantly decreased with altitude while the contribution from smaller trees was constant. Tree height and basal area also decreased significantly with increasing altitude, whereas stem density increased. While maximum potential tree height significantly decreased, wood specific gravity displayed no trend along the gradient. In particular, we showed that AGB variation was mainly determined by shift in species composition because large tree species were filtered out in the highest altitudes. Hence, our work further highlight the need for studying the drivers of large tree species distribution to better understand forest carbon stock variations in tropical forests. At the regional level, the Ngovayang massif was among the richest sites with highest level of biomass. Our results have strong implications in decisions on balancing carbon sequestration strategies with biodiversity conservation ones. Policy consequences are particularly relevant in forest management and land use planning.(Texte intégral

Disentangling the origins of cultivated sweet potato (Ipomoea batatas (L.) Lam.)

Sweet potato (Ipomoea batatas (L.) Lam., Convolvulaceae) counts among the most widely cultivated staple crops worldwide, yet the origins of its domestication remain unclear. This hexaploid species could have had either an autopolyploid origin, from the diploid I. trifida, or an allopolyploid origin, involving genomes of I. trifida and I. triloba. We generated molecular genetic data for a broad sample of cultivated sweet potatoes and its diploid and polyploid wild relatives, for noncoding chloroplast and nuclear ITS sequences, and nuclear SSRs. Our data did not support an allopolyploid origin for I. batatas, nor any contribution of I. triloba in the genome of domesticated sweet potato. I. trifida and I. batatas are closely related although they do not share haplotypes. Our data support an autopolyploid origin of sweet potato from the ancestor it shares with I. trifida, which might be similar to currently observed tetraploid wild Ipomoea accessions. Two I. batatas chloroplast lineages were identified. They show more divergence with each other than either does with I. trifida. We thus propose that cultivated I. batatas have multiple origins, and evolved from at least two distinct autopolyploidization events in polymorphic wild populations of a single progenitor species. Secondary contact between sweet potatoes domesticated in Central America and in South America, from differentiated wild I. batatas populations, would have led to the introgression of chloroplast haplotypes of each lineage into nuclear backgrounds of the other, and to a reduced divergence between nuclear gene pools as compared with chloroplast haplotypes. (Résumé d'auteur