Test de germination des graines de Caesalpinia bonduc (L.) Roxb au Bénin

La présente étude a pour objectif d’évaluer la germination des graines de deux provenances (Ouèdo/Bénin et Atakpamè/Togo) de Caesalpinia bonduc sur différents types de substrats (terreau chauffé, terreau traité aux fongicide et insecticide-nématicide et terreau non traité). Pour chacune des provenances, deux lots de 30 graines étaient considérées, les graines du premier lot étant débarrassées de leur péricarpe (amandenue) et celles du deuxième lot étant laissées telles quelles. Pour chaque lot de graines, deux répétitions ont été appliquées suivant un dispositif complètement aléatoire. Le semis a été réalisé dans des sachets de polystyrène noirs remplis de substrat. Les paramètres considérés pour chacun des traitements sont: le temps mis après semis pour la germination de la première graine et le taux final de germination. Ces paramètres ont été soumis à l’analyse de variance pour comparer les traitements appliqués aux graines, les provenances et les substrats. Ilressort de l’étude que, de façon générale, les graines non traitées mettent plus de temps à germer (16,4 jours) que celles débarrassées de leur péricarpe (13,1 jours). Par ailleurs, la provenance Atakpamè du Togo a présenté des taux de germination relativement faibles pour l’amande nue. L’étude a aussi permis de montrer que les taux de germination les plus élevés sont observés sur les substrats chauffés et non traités (41,9%). Les deux provenances garantissent, quel que soit le traitement des graines, un taux moyen de germination minimal compris entre 40 et 50%. Les résultats obtenus de la présente étude permettent alors de conseiller la technique de l’amande nue pour la provenance Ouèdo du Bénin pour améliorer les pratiques traditionnelles de propagation de l’espèce à partir de ses graines

Lantana camara (verbenaceae) : a potential threat to the effectiveness of protected areas to conserve flora and fauna in Benin

Invasive plant species are today among the biggest threats to integrity of many ecosystems including that of the protected areas. Climate change may exacerbate the negative effects of invasive plant species. Here, we used the Maximum Entropy model to project habitat suitability for Lantana camara L., an invasive plant species under current and future climates in the national protected areas network of Benin. The models were run using bioclimatic data and data on soil type. Nineteen percent of the total land in the protected areas network was highly suitable for L. camara under current climate. Highly suitable areas under current and future climates cover about 65 % of the Pendjari Biosphere Reserve, the major wildlife sanctuary in Benin. Other bio-reserves such as W National Park, Lama, Agoua, Dogo-Kétou, Atchérigbé, Mékrou and Kouandé Forest Reserves were also suitable for the species. Presence of L. camara in the protected areas represents a great potential threat to the global food webs being conserved. Based on these results, areas with highly suitable habitats are at high risk of invasion by L. camara, and should be accorded high priority when formulating appropriate management strategies.Keywords: Invasive species ; Climate change ; Habitat suitability ; Protected areas ; West AfricaLantana camara et les aires protegees au BeninLes espèces invasives font de nos jours partie des plus importantes menaces aux quelles font face les écosystèmes y compris les aires protégées. Les changements climatiques peuvent amplifier leurs effets négatifs. Dans la présente étude, nous avons utilisé un algorithme de modélisation de niche écologique, le Maximum Entropy pour analyser la susceptibilité des habitats à être colonisés par Lantana camara L., une plante invasive, sous les conditions climatiques actuelles et futures dans les aires protégées du Bénin. Les modèles ont été établis en utilisant des données bioclimatiques et des données relatives aux types de sol. Dans les conditions climatiques actuelles, 19 % de la superficie totale du réseau des aires protégées est significativement favorable à L. camara. Sous les conditions climatiques actuelles et futures, 65 % de la réserve de biosphère de Pendjari, le plus important sanctuaire de faune sauvage du Bénin, est hautement favorable à l’espèce. D’autres bio-réserves telles que le Parc National W et les reserves forestières de Lama, Agoua, Dogo-Kétou, Atchérigbé, Mékrou et Kouandé ont aussi des habitats favorable à l’espèce. En nous fondant sur ces résultats, les zones favorables sont à haut risque d’invasion par L. camara et  devraient être priorisées lors de la formulation de stratégies préventives appropriées.Mots clés: Espèces envahissantes ; Changements Climatiques ; Habitats favorables ; Aires protégées, Afrique de l’Ouest

Knowledge of diversity of wild palms (arecaceae) in the Republic of Benin: finding gaps in the national inventory by combining field and digital accessible knowledge

—Despite efforts by researchers worldwide to assess the biodiversity of plant groups, many locations on Earth remain poorly surveyed, resulting in inadequate or biased knowledge. Robust estimates of inventory completeness could help alleviate the problem. This study aimed to identify areas representing gaps in current knowledge of African palms, with a focus on Benin (West Africa). We assessed the completeness of knowledge of African palms, targeting geographic distance and climatic difference from well-known sites. Data derived from intensive fieldwork were combined with independent data available online. Inventory completeness indices were calculated and coupled with other criteria. Results showed a high overall value for inventory completeness, as well as an even distribution of well-known areas across the country. However, poorly-known areas were identified, which were in remote locations with low accessibility. This study illustrates how biodiversity survey and inventory efforts can be guided by existing knowledge. We strongly recommend the combination of digital accessible knowledge and fieldwork, coupled with expert knowledge, to obtain a better picture of inventory completeness in tropical ecosystems

Habitat range shift and prediction of the potential future distribution of Ricinodendron heudelotii (Baill.) Heckel in Benin (West Africa)

Open Access ArticleRicinodendron heudelotii (Baill.) Heckel is an important nutraceutical reservoir. Its Sustainable exploitation requires information on its potential distribution in the current context of rapid population growth and climate change threats. This study aimed to map the suitable areas for its domestication and conservation under current and future climate conditions in Benin. Occurrence data were recorded and combined with the environmental layers of two climatic scenarios (optimistic RCP 4.5 and pessimistic RCP 8.5) following the biodiversity modelling approach (biomod2). Currently, about four percent (5082 Km2) of the country’s area mainly located in the sub-humid and the humid zones were potentially suitable for R. heudelotii distribution. Under future climatic conditions the potentially suitable areas were mainly in the sub-humid zone, but almost all the highly suitable areas located in the humid zone will become medium suitable areas by the years 2055 and 2085 horizons. This study shows that, whatever the future climatic scenarios, R. heudelotii will substantially maintain the size of its range across the country. These findings allow undertaking anticipated actions to better adapt to the potential effects of climate change and to better guide policies for the conservation and development of forest resources

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Phylogenomic approaches reveal how climate shapes patterns of genetic diversity in an African rain forest tree species

The world's second largest expanse of tropical rainforest is in Central Africa, and it harbours enormous species diversity. Population genetic studies have consistently revealed significant structure across Central African rainforest plants. In particular, previous studies have repeatedly demonstrated a north-south genetic discontinuity around the equatorial line, in a continuous expanse of rainforest where a climatic inversion is documented. Here, we took a phylogeographic approach by sequencing 351 nuclear markers in 112 individuals across the distribution of the African rainforest tree speciesAnnickia affinis(Annonaceae). We showed for the first time that the north-south divide is the result of a single, major colonization event across the climatic inversion from an ancestral population located in Gabon. We suggested that differences in ecological niche of populations located on either side of this inversion may have contributed to this phylogenetic discontinuity. We found evidence for inland dispersal, predominantly in northern areas, and variable demographic histories among genetic clusters, indicating that populations responded differently to past climate change. We show how newly developed genomic tools can provide invaluable insights into our understanding of tropical rainforest evolutionary dynamics

Survey of Loxodonta africana (Elephantidae)-caused bark injury on Adansonia digitata (Malavaceae) within Pendjari Biosphere Reserve, Benin

This study assessed the level of bark damage on baobab trees (Adansonia digitata) as caused by elephants (Loxodonta africana), and the possibility of finding refuges where baobab could escape bark damage within the Pendjari Biosphere Reserve (PBR). Distributions of elephants and baobab trees within the PBR were compared using presence records of both species taken along transect lines. Two sites (National Park vs. hunting zone) that differ in elephant density were compared for intensity of bark damage and correlations between the intensity of bark damage and stem size of the baobab trees and population structure of the baobab trees. Elephants and baobabs showed co-occurrence in PBR suggesting that there is nowhere to hide for baobabs. The intensity of bark damage was positively correlated with elephant density and baobab girth. Baobab population girth classes were not significantly different in areas with and without bark damage. Future studies should test whether there are certain baobab genotypes that can resist elephant damage. It could also be tested whether effective conservation of elephants in the PBR has resulted in a bull-biased population over its carrying capacity