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See detailA few north Appalachian populations are the source of European black locust
Bouteiller, Xavier; Verdu, C.F; Aikio, E et al

in Ecology and Evolution (2019), 9(5), 2398-2414

The role of evolution in biological invasion studies is often overlooked. In order to evaluate the evolutionary mechanisms behind invasiveness, it is crucial to identify the source populations of the ... [more ▼]

The role of evolution in biological invasion studies is often overlooked. In order to evaluate the evolutionary mechanisms behind invasiveness, it is crucial to identify the source populations of the introduction. Studies in population genetics were carried out on Robinia pseudoacacia L., a North American tree which is now one of the worst invasive tree species in Europe. We realized large-scale sampling in both the invasive and native ranges: 63 populations were sampled and 818 individuals were genotyped using 113 SNPs. We identified clonal genotypes in each population and analyzed between and within range population structure, and then, we compared genetic diversity between ranges, enlarging the number of SNPs to mitigate the ascertainment bias. First, we demonstrated that European black locust was introduced from just a limited number of populations located in the Appalachian Mountains, which is in agreement with the historical documents briefly reviewed in this study. Within America, population structure reflected the effects of long-term processes, whereas in Europe it was largely impacted by human activities. Second, we showed that there is a genetic bottleneck between the ranges with a decrease in allelic richness and total number of alleles in Europe. Lastly, we found more clonality within European populations. Black locust became invasive in Europe despite being introduced from a reduced part of its native distribution. Our results suggest that human activity, such as breeding programs in Europe and the seed trade throughout the introduced range, had a major role in promoting invasion; therefore, the introduction of the missing American genetic cluster to Europe should be avoided. © 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. [less ▲]

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See detailConservation value of protected and logged tropical forests in Cameroon
Lhoest, Simon ULiege; Fonteyn, Davy ULiege; Daïnou, Kasso ULiege et al

Scientific conference (2019, January 25)

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See detailGrowth determinants of timber species Triplochiton scleroxylon and implications for forest management in central Africa
Ligot, Gauthier ULiege; Fayolle, Adeline ULiege; Gourlet-Fleury, Sylvie et al

in Forest Ecology and Management (2019), 437

The sustainability of the polycyclic logging system in tropical forests has been increasingly questioned for a variety of reasons, and particularly in central Africa as commercial species, mostly light ... [more ▼]

The sustainability of the polycyclic logging system in tropical forests has been increasingly questioned for a variety of reasons, and particularly in central Africa as commercial species, mostly light-demanding long-lived pioneer species, usually fail to recover a stable number of large trees after exploitation. Several factors are known to affect tropical tree demographic processes, like tree growth, survival and recruitment. Tree growth has particularly been showed to depend on ecological conditions, tree genetics, and competition with surrounding vegetation, as well as tree size or ontogeny. Yet, due to the paucity of available data, the importance of such factors is unclear and usually ignored when estimating future timber yields. To fill this gap, we chose to evaluate the variability in growth of one African long-lived pioneer and commercially very important species: Triplochiton scleroxylon K. Schum, gathering a broad dataset composed of tree ring data recorded in one site in Cameroon and periodic field inventory data recorded in seven sites across central Africa. In total, we analyzed 13,225 records of annual tree diameter increments recorded over 920 trees from seven sites in Cameroon, Republic of the Congo and Central African Republic. We evaluated (i) to what extent the average growth of trees that reach harvestable dimensions differs from population average and (ii) to what extent past perturbations influence the growth of remaining trees. We found the diameter growth of T. scleroxylon to be remarkably variable and this study provided an unprecedented quantification of the magnitude of some key growth determinants. In unlogged forests, the diameter increment of T. scleroxylon ranged between 0.40 cm year-1 in Southern Cameroon and 0.83 cm year-1 in South-Eastern Cameroon. The diameter increment was weakly related to tree size but increased twofold from unlogged to logged forests. Perturbation caused by logging stimulates growth of T. scleroxylon for at least 10-15 years. Finally, harvestable timber stock of large-sized T. scleroxylon was found to be constituted by trees that grew in average twice faster than trees of the entire extant population. As more and more inventory data become available, quantifying these effects could be replicated for other timber species and in other sites, to improve the accuracy of future timber resource estimates and improve forest management guidelines. [less ▲]

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See detailBanque de graines du sol et déterminants de la germination du tali, Erythrophleum suaveolens (Guill. & Perr.) Brenan
Douh, Chauvelin ULiege; Gorel, Anaïs ULiege; Daïnou, Kasso ULiege et al

in Bois et Forêts des Tropiques (2018), 338

Cette étude évalue l’abondance des graines d’Erythrophleum suaveolens dans la banque du sol des forêts denses humides d’Afrique centrale. Les travaux ont été menés au Nord-Congo dans deux types forestiers ... [more ▼]

Cette étude évalue l’abondance des graines d’Erythrophleum suaveolens dans la banque du sol des forêts denses humides d’Afrique centrale. Les travaux ont été menés au Nord-Congo dans deux types forestiers : la forêt à Celtis sur des sols argilo-sableux à sablo-argileux et la forêt à Manilkara sur des sols sableux. Les tiges d’E. suaveolens (dhp ≥ 10 cm) ont été inventoriées dans deux parcelles de 400 ha, et les structures diamétriques de leurs populations ont été comparées. En outre, 80 fosses (2 x 40 fosses par type de forêt) ont été creusées aux pieds de 20 arbres (10 par forêt), sur trois couches contiguës de 10 cm chacune, soit à une profondeur totale de 30 cm, et l’abondance des graines dans la banque du sol a été évaluée. La dormance des graines récoltées a été testée par des essais de germination après traitement au H2SO4 et cinq graines prélevées jusqu’à une profondeur de 20 cm dans la forêt à Celtis ont été utilisées pour estimer leur âge par Spectroscopie de Masse par Accélérateur (SMA). La comparaison des structures diamétriques indique une plus grande proportion de tiges de faible diamètre dans la forêt à Celtis. Alors que les densités de tiges (dhp ≥ 10 cm) sont proches, avec 0,85 et 1,05 tige/ha respectivement, dans la forêt à Celtis et la forêt à Manilkara, les densités de graines sont significativement plus élevées dans la forêt à Celtis (8,55 graines/m2) que dans la forêt à Manilkara (0,15 graine/m2). Le pourcentage maximum de germination obtenu était de 19,1 % pour des graines n’ayant subi aucun traitement. Les lots traités à l’acide ont présenté de moindres taux de germination. Ces graines pourraient se conserver une dizaine d’années dans la banque du sol. Les facteurs pouvant influencer les variations de densité des graines sont discutés et des recommandations sylvicoles sont formulées. [less ▲]

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See detailThe size at reproduction of canopy tree species in central Africa
Ouedraogo, Dakis-Yaoba ULiege; Doucet, Jean-Louis ULiege; Daïnou, Kasso ULiege et al

in Biotropica (2018), 50(3), 465-476

Size at reproduction is a key aspect of species life history that is relatively understudied for long-lived tropical trees. Here, we quantified reproductive diameter for 31 major timber species across 11 ... [more ▼]

Size at reproduction is a key aspect of species life history that is relatively understudied for long-lived tropical trees. Here, we quantified reproductive diameter for 31 major timber species across 11 sites in Cameroon, Congo, and Central African Republic. Specifically, we examined whether (1) between-species variability is correlated with other species traits; (2) reproductive diameter varies within-species among sites; (3) reproductive status varies with crown exposure; and (4) the minimum cutting diameter limits (MCDL) imposed by national forest regulations enable seed trees to persist after logging operations. Consistent with studies conducted elsewhere in the tropics, we found great variability in diameter at reproduction among species, which correlated with adult stature (maximum diameter and height). For some species, reproductive diameter thresholds substantially varied between sites, and crown exposure had a significant positive effect on reproductive status. Most MCDLs were found to be suitable, with trees having a high probability of being seed trees at MCDL. Our findings have implications for the sustainable management of production forests, and they highlight questionable MCDLs for some species and between-site variation in reproductive diameter. The study also highlights the need for long-term phenological monitoring of tree species spanning a large range of ecological strategies to address both theoretical (species life history, allocation tradeoffs) and practical questions (MCDL). [less ▲]

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See detailSoil seed bank characteristics in two central African forest types and implications for forest restoration
Douh, Chauvelin ULiege; Daïnou, Kasso ULiege; Joël Loumeto, J. et al

in Forest Ecology and Management (2018), 409

This study evaluates the characteristics of soil seed bank in two types of central African rainforests: Celtis forest on clay soils and Manilkara forest on sandy soils. In each study site, 30 samples were ... [more ▼]

This study evaluates the characteristics of soil seed bank in two types of central African rainforests: Celtis forest on clay soils and Manilkara forest on sandy soils. In each study site, 30 samples were collected per soil layers (litter, 0–5 cm, 5–10 cm and 10–20 cm depth). The species diversity and abundance of the soil seed bank were estimated after soil samples were brought to germination. We globally observed 297 seedlings of 53 species for the Celtis forest and 222 seedlings of 39 species for the Manilkara forest. The total densities of germinated seeds were 330 seedlings m−2 and 247 seedlings m−2, respectively. Herbaceous species dominated with percentages of 41.0 and 45.3%, respectively in the Manilkara forest and the Celtis forest. Both forest types displayed a regeneration potential through the soil seed bank. However, this potential seems higher in the Celtis forest. Pioneer taxa were more abundant in the soil seed bank of the Celtis forest (13 woody pioneer species) than the Manilkara forest (9 woody pioneer species). The values of Sorensen similarity index between the standing tree vegetation and the soil seed bank in each site were relatively low: 11.0% for the Celtis forest and 8.8% for the Manilkara forest. But these similarity values were higher when only the pioneer species were considered: 46.8% in the Celtis forest and 38.9% in the Manilkara forest. The highest species richness were obtained in the first two soil layers (0–10 cm depth) while 21.8% and 21.4% of the species were exclusively found in the deepest layer (10–20 cm) in the Celtis forest and the Manilkara forest, respectively. Among the timber species found in the forest, only three were observed in the soil seed bank of the two sites: Nauclea diderrichii, Erythrophleum suaveolens and Staudtia kamerunensis. N. diderrichii was particularly abundant in the soil seed stock of the two sites (14.4–34.4 seeds m−2). Results suggested that to improve regeneration of timber species, planting in open forest habitats with seedlings coming from tree nursery should be more efficient. © 2017 Elsevier B.V. [less ▲]

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See detailProjet Flux de gènes. Aide à l'application des normes d’aménagement et de certification sur la régénération et la diversité génétique des essences du bassin du Congo.
Daïnou, Kasso ULiege; Donkpegan Segbedji, Armel Loïc; Doucet, Jean-Louis ULiege et al

Conference given outside the academic context (2017)

Contexte • Peu de connaissances sur l’écologie des essences commerciales, dont les processus intervenant dans la régénération • Très peu d’informations sur l’impact de l’exploitation forestière sur la ... [more ▼]

Contexte • Peu de connaissances sur l’écologie des essences commerciales, dont les processus intervenant dans la régénération • Très peu d’informations sur l’impact de l’exploitation forestière sur la régénération des essences commerciales Or exigences croissantes, notamment : • Normes de gestion durable des forêts de production, dont la circulaire 0086 relative à la sylviculture • Normes de certification, dont le critère FSC 6.3 relatif à la régénération et au maintien de la diversité génétique Objectifs : Mieux comprendre les processus en amont de la régénération et proposer des normes d’exploitation considérant la diversité génétique 1. Estimer les distances de dispersion du pollen et des graines, par des outils de biologie moléculaire (tests de parenté et de paternité) 2. Etudier l’effet de l’isolement spatial sur le succès reproducteur, par l’évaluation des niveaux de consanguinité et d’autofécondation, l’écologie classique [less ▲]

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See detailDevelopment of nuclear SNP markers for genetic tracking of Iroko, Milicia excelsa and Milicia regia
Blanc-Jolivet, Céline; Kersten, Birgit; Daïnou, Kasso ULiege et al

in Conservation Genetics Resources (2017)

Iroko, Milicia excelsa, is an economically important tropical hardwood species widely distributed in tropical Africa, from Ivory Coast in Western Africa to Tanzania in Eastern Africa. The species occurs ... [more ▼]

Iroko, Milicia excelsa, is an economically important tropical hardwood species widely distributed in tropical Africa, from Ivory Coast in Western Africa to Tanzania in Eastern Africa. The species occurs at low densities in contrasting habitats such as rainforest and woodlands. Former studies using chloroplast and nuclear sequences, as well as nSSRs, revealed a strong differentiation within the species among West and Central African populations and the presence of three genetic groups in Central Africa (Daïnou et al. 2010, 2014). The genus Milicia also includes another species, M. regia, co-occurring with M. excelsa in West Africa. Both species can be identified genetically and morphologically (Daïnou et al. 2014), but identification is difficult in the field. Although the spatial genetic structure of the species is well described, it is mostly based on nSSRs. Despite their lower diversity, SNP markers provide several advantages including the uncomplicated standardization of data among laboratories and the easy, rapid and low-cost development of markers for large sets of loci. These features make SNPs the ideal markers for setting up genetic reference data for timber tracking (Blanc-Jolivet and Liesebach 2015; Degen et al. 2017; Jardine et al. 2016; Pakull et al. 2016). In this paper, we describe the development of a new set of nuclear SNPs on M. excelsa meant to be used for genetic timber tracking. [less ▲]

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See detailEntandrophragma cylindricum (Sprague) Sprague (Meliaceae), une espèce ligneuse concurrentielle en Afrique centrale (synthèse bibliographique)
Tabi Eckebil, Paule ULiege; Verheggen, François ULiege; Doucet, Jean-Louis ULiege et al

in Biotechnologie, Agronomie, Société et Environnement (2017), 21(1), 80-97

Introduction. De nos jours, la gestion des ressources forestières ne se focalise plus sur l’exploitation exclusive du bois d’oeuvre, mais prend également en considération les produits forestiers non ... [more ▼]

Introduction. De nos jours, la gestion des ressources forestières ne se focalise plus sur l’exploitation exclusive du bois d’oeuvre, mais prend également en considération les produits forestiers non ligneux. Entandrophragma cylindricum (Sprague) Sprague, de son nom commercial « sapelli/sapele », de la famille des Meliaceae, illustre parfaitement cette situation. Le présent article fait un état de l’art des connaissances concernant E. cylindricum et présente quelques informations sur la chenille qui lui est inféodée. Littérature. Le sapelli est une des espèces ligneuses les plus exploitées d’Afrique centrale pour son bois d’oeuvre. Il est répandu dans la forêt dense humide semi-caducifoliée du domaine guinéo-congolais. C’est une espèce semi-héliophile, son mode de dispersion est anémochore et sa phénologie est régulière. Selon la sylviculture appliquée, sa croissance en diamètre peut atteindre jusque 0,82 cm par an. Cette essence est également l’hôte d’une espèce de chenille comestible riche en protéines, I. oyemensis Rougeot. Fortement appréciée par les populations locales, cette chenille fait également l’objet d’un commerce régional et international. Enfin, l’écorce du sapelli est reconnue pour son intérêt ethnobotanique, particulièrement en médecine traditionnelle. Conclusions. Les informations tirées de la littérature ont permis de mettre en évidence certaines lacunes relatives à l’écologie et au mode de reproduction de cette espèce et, ceci, en dépit de son importance pour le commerce du bois. De plus, les inconnues quant à la productivité et la saisonnalité des chenilles d’Imbrasia oyemensis sur cet arbre nécessitent de développer des recherches complémentaires pour garantir la durabilité de l’exploitation simultanée de la ressource ligneuse et non ligneuse et pour proposer des modes de gestion concertés entre exploitants industriels et populations locales. [less ▲]

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See detailA look at Intact Forest Landscapes and their relevance to Central African forest policy
Haurez, Barbara ULiege; Daïnou, Kasso ULiege; Vermeulen, Cédric ULiege et al

Conference (2017, February)

Tropical forests are important providers of natural resources and ecosystem services but their ecological functions are facing increasing human pressure, linked to economic development. The preservation ... [more ▼]

Tropical forests are important providers of natural resources and ecosystem services but their ecological functions are facing increasing human pressure, linked to economic development. The preservation of tropical forest ecosystems is interrelated with effective land use planning and identification of priority areas for conservation. Initially defined by Greenpeace and the World Resources Institute (WRI) in 2000, Intact Forest Landscapes (IFLs) are large areas of forest minimally impacted by human activities. IFLs were identified by mapping industrial activities, road networks and infrastructure using remote sensing. Since 2014, when IFLs were recognized and adopted by the certification scheme Forest Stewardship Council (FSC), the IFLs have become integrated into forest management policies. In order to trace the history and evaluate the applicability of IFLs for forest management policy in the Central African context, we searched for documents related to the IFL method, and previous similar concepts. The IFL method is simple and cost-effective and enables the monitoring of forest degradation at a global scale. However, the approach mainly considers forest cover and is imprecise at the local scale. For example, hunting, one of the main threats faced by Central African ecosystems, cannot be detected by satellite imagery and is therefore disregarded in IFL identification processes. In contrast, there are other considered anthropogenic activities, such as reduced-impact selective logging, which may be compatible with forest ecosystem conservation. To better tailor the IFL approach to Central African forests, we recommend (i) the consideration of wildlife communities distribution in the analysis of disturbance, (ii) a thorough evaluation of the impacts of different human activities on forest ecosystems, and (iii) the integration of local stakeholders and governments in the design of land management strategies devised to address social, economic and environmental needs. [less ▲]

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See detailDNA taxonomy in the timber genus Milicia: evidence of unidirectional introgression in the West African contact zone
Daïnou, Kasso ULiege; Flot, J.-F.; Degen, B. et al

in Tree Genetics and Genomes (2017), 13(4),

DNA-based techniques are helpful in characterising hybridisation patterns in plant species. To be efficient in disentangling species boundaries and interspecific gene flow, it is recommended to combine ... [more ▼]

DNA-based techniques are helpful in characterising hybridisation patterns in plant species. To be efficient in disentangling species boundaries and interspecific gene flow, it is recommended to combine various methodologies and types of markers. Here, we used different analytical tools (algorithms implemented in Structure, Tess, NewHybrids and HIest, and the haploweb approach) and three nuclear genetic markers (7 nuclear simple sequence repeat loci (SSRs), 62 single-nucleotide polymorphism loci (SNPs) and a single-copy gene region, At103) to revisit hybridisation patterns in the commercially important African tree genus Milicia. Samples were collected in the natural ranges of Milicia regia and Milicia excelsa in West Africa. Using real data sets, simulated purebreds and hybrid genotypes, we found that SNPs yielded results more consistent than SSRs; outputs from the Bayesian and maximum-likelihood analyses differed significantly using the SSRs, whereas they were perfectly congruent using SNPs. A proportion of 12.4% hybrids were detected amongst the SNP genotype samples. A haploweb analysis of At103 gene sequences confirmed the existence of interspecific hybrids. There was also a clear evidence of advanced generations of hybrids (backcrossed individuals) but only towards M. regia. Although more investigation is required for understanding the mechanisms responsible for this asymmetric introgression, we suggest that it may be due to the differences in flowering time between species and between sexes, combined with a maternal inheritance of flowering time. © 2017, Springer-Verlag GmbH Germany. [less ▲]

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See detailGuide technique. Plantation agroforestière d'Acacia auriculiformis dans le Haut-Katanga
Boldrini, Sylvie; Bracke, Charles; Daïnou, Kasso ULiege et al

Book published by Presses Agronomiques de Gembloux (2017)

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See detailA look at Intact Forest Landscapes and their relevance in Central African forest policy
Haurez, Barbara ULiege; Daïnou, Kasso ULiege; Vermeulen, Cédric ULiege et al

in Forest Policy and Economics (2017), 80

Tropical forests are major providers of natural resources and ecosystem services but their ecological functions are at threat, due to increasing human pressure linked to economic development. The ... [more ▼]

Tropical forests are major providers of natural resources and ecosystem services but their ecological functions are at threat, due to increasing human pressure linked to economic development. The identification of priority areas for conservation is crucial for land use planning to ensure the protection of biodiversity and ecological function. Intact Forest Landscapes (IFLs), as defined by Greenpeace and World Resources Institute (WRI), are areas of the forest ecosystems not subjected to human activities. They have beenidentified by mapping human disturbances through remote sensing. Contrary to similar global-scale concepts, IFLs have been integrated into the standards of the certification body Forest Stewardship Council (FSC) and therefore have practical implications for forest management policies. The Motion 65, approved in the general assembly of FSC in 2014, mandates the protection of IFLs located in FSC certified logging concessions. Until the implementation of national standards, forestry operations are banished from 80% of the IFL area within each forest management unit. To trace the history and evaluate the suitability of IFLs in the Central African context, we searched for documents related to the IFL method, and related approaches focusing on the identification of areas devoid of human disturbances. The IFL method is simple and cost-effective and allows for a global assessment of the influence of human infrastructures and industrial exploitation on forests However, the method does not consider the situation below the canopy and those forest components not visible by satellites. For example, hunting, one of the main threats faced by wildlife in Central African forests today, cannot be detected with satellite imagery. On the other hand, other anthropogenic activities which remote sensing may detect may be compatible with forest ecosystem conservation. To better tailor the IFL approach to Central African forests, we recommend (i) the consideration of wildlife communities in the intactness analysis, (ii) a thorough evaluation of the impacts of human activities on forest ecosystems, and (iii) the integration of local stakeholders and governments in the design of land management strategies to respond to social, economic and environmental needs [less ▲]

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See detailThe influence of spatially structured soil properties on tree community assemblages at a landscape scale in the tropical forests of southern Cameroon
Vleminckx, Jason; Doucet, Jean-Louis ULiege; Morin, Julie ULiege et al

in Journal of Ecology (2016)

Species distribution within plant communities results from both the influence of deterministic processes, related to environmental conditions, and neutral processes related to dispersal limitation and ... [more ▼]

Species distribution within plant communities results from both the influence of deterministic processes, related to environmental conditions, and neutral processes related to dispersal limitation and stochastic events, the relative importance of each factor depending on the observation scale. Assessing the relative contribution of environment necessitates controlling for spatial dependences among data points. Recent methods, combining multiple regression and Moran's eigenvectors maps (MEM), have been proved successful in disentangling the influence of pure spatial processes related to dispersal limitation, pure environmental variables (not spatially structured) and spatially structured environmental properties. However, the latter influence is usually not testable when using advanced spatial models like MEM. To overcome this issue, we propose an original approach, based on torus-translations and Moran spectral randomizations, to test the fraction of species abundance variation that is jointly explained by space and seven soil variables, using three environmental and tree species abundance data sets (consisting of 120, 52 and 34 plots of 0·2 ha each, located along 101-, 66- and 35-km-long transect-like inventories, respectively) collected in tropical moist forests in southern Cameroon. The overall abundance of species represented by ≥30 individuals, and 27% of these species taken individually, were significantly explained by fine-scale (<5 km) and/or broad-scale (5–100 km) spatially structured variations in soil nutrient concentrations (essentially the concentration of available Mn, Mg and Ca) along the 120-plots area. The number of significant tests considerably decreased when investigating the two smaller data sets, which mostly resulted from low statistical power rather than weaker floristic and/or edaphic variation captured among plots. Synthesis. Our results provide evidence that tree species turnovers are partly controlled by spatially structured concentrations in soil nutrients at scales ranging from few hundreds of metres to c. 100 km, a poorly documented subject in Central African forests. We also highlight the usefulness of our testing procedure to correctly interpret the space-soil fraction of variation partitioning analyses (which always accounted here for the most important part of the soil contribution), as this fraction was sometimes relatively high (R2 values up to c. 0·3) but nearly or not significant. [less ▲]

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See detailRevealing hidden species diversity in closely related species using nuclear SNPs, SSRs and DNA sequences - a case study in the tree genus Milicia
Daïnou, Kasso ULiege; Blanc-Jolivet, Céline; Degen, Bernd et al

in BMC Evolutionary Biology (2016), 16(259), 15

Background: Species delimitation in closely related plant taxa can be challenging because (i) reproductive barriers are not always congruent with morphological differentiation, (ii) use of plastid ... [more ▼]

Background: Species delimitation in closely related plant taxa can be challenging because (i) reproductive barriers are not always congruent with morphological differentiation, (ii) use of plastid sequences might lead to misinterpretation, (iii) rare species might not be sampled. We revisited molecular-based species delimitation in the African genus Milicia, currently divided into M. regia (West Africa) and M. excelsa (from West to East Africa). We used 435 samples collected in West, Central and East Africa. We genotyped SNP and SSR loci to identify genetic clusters, and sequenced two plastid regions (psbA-trnH, trnC-ycf6) and a nuclear gene (At103) to confirm species’ divergence and compare species delimitation methods. We also examined whether ecological niche differentiation was congruent with sampled genetic structure. Results: West African M. regia, West African and East African M. excelsa samples constituted three well distinct genetic clusters according to SNPs and SSRs. In Central Africa, two genetic clusters were consistently inferred by both types of markers, while a few scattered samples, sympatric with the preceding clusters but exhibiting leaf traits of M. regia, were grouped with the West African M. regia cluster based on SNPs or formed a distinct cluster based on SSRs. SSR results were confirmed by sequence data from the nuclear region At103 which revealed three distinct ‘Fields For Recombination’ corresponding to (i) West African M. regia, (ii) Central African samples with leaf traits of M. regia, and (iii) all M. excelsa samples. None of the plastid sequences provide indication of distinct clades of the three species-like units. Niche modelling techniques yielded a significant correlation between niche overlap and genetic distance. Conclusions: Our genetic data suggest that three species of Milicia could be recognized. It is surprising that the occurrence of two species in Central Africa was not reported for this well-known timber tree. Globally, our work highlights the importance of collecting samples in a systematic way and the need for combining different nuclear markers when dealing with species complexes. Recognizing cryptic species is particularly crucial for economically exploited species because some hidden taxa might actually be endangered as they are merged with more abundant species. [less ▲]

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See detailEvolution in African tropical trees displaying ploidy-habitat association: The genus Afzelia (Leguminosae)
Donkpegan, Segbedji ULiege; Doucet, Jean-Louis ULiege; Migliore, Jérémy et al

in Molecular Phylogenetics and Evolution (2016)

Polyploidy has rarely been documented in rain forest trees but it has recently been found in African species of the genus Afzelia (Leguminosae), which is composed of four tetraploid rain forest species ... [more ▼]

Polyploidy has rarely been documented in rain forest trees but it has recently been found in African species of the genus Afzelia (Leguminosae), which is composed of four tetraploid rain forest species and two diploid dry forest species. The genus Afzelia thus provides an opportunity to examine how and when polyploidy and habitat shift occurred in Africa, and whether they are associated. In this study, we combined three plastid markers (psbA, trnL, ndhF), two nuclear markers (ribosomal ITS and the single-copy PEPC E7 gene), plastomes (obtained by High Throughput Sequencing) and morphological traits, with an extensive taxonomic and geographic sampling to explore the evolutionary history of Afzelia. Both nuclear DNA and morphological vegetative characters separated diploid from tetraploid lineages. Although the two African diploid species were well differentiated genetically and morphologically, the relationships among the tetraploid species were not resolved. In contrast to the nuclear markers, plastid markers revealed that one of the diploid species forms a well-supported clade with the tetraploids, suggesting historical hybridisation, possibly in relation with genome duplication (polyploidization) and habitat shift from dry to rain forests. Molecular dating based on fossil-anchored gene phylogenies indicates that extant Afzelia started diverging c. 14.5 or 20 Ma while extant tetraploid species started diverging c. 7.0 or 9.4 Ma according to plastid and nuclear DNA, respectively. Additional studies of tropical polyploid plants are needed to assess whether the ploidy-habitat association observed in African Afzelia would reflect a role of polyploidization in niche divergence in the tropics. [less ▲]

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See detailHautes Valeurs de Conservation (HVC) dans les Unités Forestières d'Aménagement du Cameroun : concepts, choix et pratiques
Daïnou, Kasso ULiege; Bracke, Charles; Vermeulen, Cédric ULiege et al

Book published by Presses Agronomiques de Gembloux (2016)

Le système de certification FSC (Forest Stewardship Council) vise à promouvoir la gestion durable des forêts. Il repose sur un ensemble de normes dont une est particulièrement complexe à mettre en oeuvre ... [more ▼]

Le système de certification FSC (Forest Stewardship Council) vise à promouvoir la gestion durable des forêts. Il repose sur un ensemble de normes dont une est particulièrement complexe à mettre en oeuvre en Afrique Centrale, le principe 9 traitant des Hautes Valeurs de Conservation (HVC). Ce principe devrait être interprété aux échelons nationaux afin de prendre en compte les spécificités de chaque pays. Bien que des ouvrages aient déjà été élaborés par diverses organisations, aucun ne cible particulièrement les grandes concessions forestières. Au Cameroun, ces concessions ou Unités Forestières d’Aménagement (UFA), représentent pourtant 40 % du domaine forestier national. Le présent guide ambitionne de fournir aux acteurs de la gestion forestière au Cameroun les connaissances les plus pertinentes afin de leur permettre d’identifier, de gérer et de suivre les Hautes Valeurs de Conservation dans les UFA. Il se démarque des précédents guides par plusieurs points : (i) une revue bibliographique détaillée est fournie sur le sujet épineux de l’identification de chaque HVC, et l’opinion des auteurs y est mise en exergue; (ii) la démarche d’identification est appuyée par les références les plus pertinentes, évitant au gestionnaire de se disperser dans sa quête de documentation; (iii) sur la base de leur expérience, les auteurs proposent une série de menaces pouvant affecter les HVC, de mesures de gestion et d’indicateurs de suivi. L’approche développée se base sur des méthodes empiriques et pragmatiques d’une part et, d’autre part, sur des études scientifiques. Cet ouvrage devrait constituer une base intéressante pour une interprétation solide des HVC au Cameroun. De plus, bien que ciblant les UFA camerounaises, il pourrait inspirer d’autres acteurs forestiers œuvrant dans le Bassin du Congo. [less ▲]

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See detailHigh spatial resolution of late-Holocene human activities in the moist forests of central Africa using soil charcoal and charred botanical remains
Morin, Julie ULiege; Biwolé, Achille; Gorel, Anaïs ULiege et al

in Holocene (2016), 26(12), 1954-1967

Palaeoecological and archaeological studies have demonstrated that human populations have long inhabited the moist forests of central Africa. However, spatial and temporal patterns of human activities ... [more ▼]

Palaeoecological and archaeological studies have demonstrated that human populations have long inhabited the moist forests of central Africa. However, spatial and temporal patterns of human activities have hardly been investigated with satisfactory accuracy. In this study, we propose to characterize past human activities at local scale by using a systematic quantitative and qualitative methodology based on soil charcoal and charred botanical remains. A total of 88 equidistant test-pits were excavated along six transects in two contrasting forest types in southern Cameroon. Charred botanical remains were collected by water-sieving and sorted by type (wood charcoals, oil palm endocarps, and unidentified seeds). A total of 50 Accelerator Mass Spectrometry 14C dates were also obtained. Results showed that charred macroremains were found at multiple places in the forest, suggesting scattered human activities, which were distributed into two main periods (Phase A: 2300-1300 BP – Phase B: 580 BP to the present). Charred botanical remains indicated two types of land use: (i) domestic, with oil palm endocarps most often associated with potsherds (villages) and (ii) agricultural, with charcoal as probable remnant of slash-and-burn cultivation (fields). Oil palm endocarp abundance decreased with distance from the identified human settlements. Our methodology allowed documenting, at high resolution, the spatial and temporal patterns of human activities in central African moist forests and could be applied to other tropical contexts. [less ▲]

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