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See detailSpecies delimitation and diversification in the widespread tree genus Milicia (Moraceae)
Daïnou, Kasso ULg; Mahy, Grégory ULg; Duminil, Jérôme et al

Conference (2013, June)

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed ... [more ▼]

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed this issue with the African timber tree genus Milicia that comprises two morphologically similar and often confounded species: M. excelsa, widespread from West to East Africa, and M. regia, endemic to West Africa. We combined information from nuclear microsatellites (nSSRs), nuclear and plastid DNA sequences, and morphological systematics to identify significant evolutionary units and infer their evolutionary and biogeographical history. We detected five geographically coherent genetic clusters using nSSRs and three levels of genetic differentiation. First, one West African cluster matched perfectly with the morphospecies M. regia, which formed a monophyletic clade at both DNA sequences. Second, a West African M. excelsa cluster formed a monophyletic group at plastid DNA and was more related to M. regia than to Central African M. excelsa, but shared many haplotypes with the latter at nuclear DNA. Third, three Central African clusters appeared little differentiated and shared most of their haplotypes. Although gene tree paraphyly could suggest a single species in Milicia following the Phylogenetic Species Concept, the existence of mutual haplotypic exclusivity and non-admixed genetic clusters in the contact area of the two taxa indicate strong reproductive isolation, and thus, two species following the Biological Species Concept. Molecular dating of the first divergence events showed that speciation in Milicia is ancient (Tertiary), indicating that long-living tree taxa exhibiting genetic speciation may remain similar morphologically. [less ▲]

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See detailNature+ asbl - Rapport d'activités 2012
Federspiel, Michèle; Doucet, Jean-Louis ULg; Daïnou, Kasso ULg et al

Report (2013)

En 2012, Nature+ a rencontré ses missions, notamment : en mettant en oeuvre trois projets de foresterie communautaire financés par des bailleurs internationaux ; en participant à la gestion durable de ... [more ▼]

En 2012, Nature+ a rencontré ses missions, notamment : en mettant en oeuvre trois projets de foresterie communautaire financés par des bailleurs internationaux ; en participant à la gestion durable de près de 2,7 millions d’hectares de forêts denses humides tropicales grâce à nos collaborations avec des sociétés forestières engagées dans les processus de certification FSC ; en accueillant dans nos divers projets 10 étudiants en fin de cursus universitaire ainsi que 11 doctorants. Huit universités différentes ont ainsi reçu un appui administratif, technique et scientifique de Nature+ ; en attribuant sa 2eme bourse de formation à un chercheur congolais. [less ▲]

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See detailEssais de propagation par semis et marcottage aérien de Coula edulis Baill. et perspectives pour sa domestication
Moupela, Christian; Doucet, Jean-Louis ULg; Daïnou, Kasso ULg et al

in Bois et Forêts des Tropiques (2013), 318(4), 3-13

Le noisetier d’Afrique, Coula edulis Baill. Olacaceae, est un arbre des forêts denses humides africaines. Il produit des graines d’une grande valeur nutritive qui sont régulièrement récoltées et ... [more ▼]

Le noisetier d’Afrique, Coula edulis Baill. Olacaceae, est un arbre des forêts denses humides africaines. Il produit des graines d’une grande valeur nutritive qui sont régulièrement récoltées et commercialisées par les populations d’Afrique centrale et de l’Ouest. Cependant, le manque d’informations relatives aux techniques de multiplication de l’espèce est la principale contrainte à sa domestication et à son intégration dans les systèmes agroforestiers locaux. L’étude, conduite parallèlement en pépinière et en milieu naturel, vise à mieux caractériser la germination de C. edulis et à déterminer ses aptitudes au marcottage aérien. Les résultats obtenus indiquent que la germination de C. edulis est très lente et échelonnée avec des taux de levée très faibles, voire nuls. De plus, les prétraitements appliqués aux graines se sont révélés inefficaces pour améliorer la vitesse et le taux de levée des semences. En revanche, le marcottage aérien permet de produire des plants de C. edulis d’une vigueur bien supérieure et dans un délai plus court que les semis en pépinière. Les résultats préliminaires du marcottage aérien sont prometteurs et ouvrent des perspectives intéressantes pour la multiplication et la domestication de l’espèce. L’intégration de Coula edulis dans les systèmes agroforestiers des plants issus du marcottage aérien est donc envisageable. [less ▲]

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See detailDispersal and predation of diaspores of Coula edulis Baill. in an evergreen forest of Gabon
Moupela, Christian ULg; Doucet, Jean-Louis ULg; Daïnou, Kasso ULg et al

in African Journal of Ecology (2013), 52

The African walnut ( Coula edulis) is a tree species of African evergreen forests, the seeds of which are collected and traded by African people. Many animal species consume African walnut diaspores ... [more ▼]

The African walnut ( Coula edulis) is a tree species of African evergreen forests, the seeds of which are collected and traded by African people. Many animal species consume African walnut diaspores; however, their roles as dispersers or predators have yet to be clarified. In this study, we present observations conducted in two different habitats of a Gabonese region over a 3-year period. The originality of this research resides in the combination of three complementary approaches: (i) the use of camera-traps (ii) the exploration of land rodent burrows and (iii) the examination of elephant dung. In total, 408 camera-trap photographs have shown seven animal species involved in the dispersal/predation of C. edulis. Among these seven frugivorous species, the bush pig was found to be the main consumer and predator of seeds. Land rodents (Muridae) are potential predators, as they damaged the seeds and buried them deep in the soil. They may also play a role in the regeneration process as a result of the loss of seeds during transportation. Finally, no seeds appeared to emerge intact from elephant faeces. These results indicate that the natural regeneration rate of this tree species is low, unless other complex mecha-nisms are involved. [less ▲]

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See detailEcology of Pericopsis elata (Fabaceae), a Timber Species Considered as Endangered, in Southeastern Cameroon
Bourland, Nils ULg; Kouadio, Yao Lambert; Lejeune, Philippe ULg et al

in Biotropica (2012), 44(6), 840-847

Pericopsis elata (Fabaceae) is a tall tree of high commercial value of the moist semi-deciduous African forests. As a result of logging which started decades ago, it is considered as threatened and ... [more ▼]

Pericopsis elata (Fabaceae) is a tall tree of high commercial value of the moist semi-deciduous African forests. As a result of logging which started decades ago, it is considered as threatened and included on both IUCN Red List and CITES Appendix II even though essential biological parameters controlling its population dynamics remain unknown. This study aims at improving the knowledge of the species ecological parameters and at assessing the impact of selective logging on its populations in an 118,052 ha forest in Cameroon. After inventorying the species in 1,432 ha, mortality and growth were assessed over continuous 5- and 2-year periods in unlogged and logged areas, respectively. Phenology was monitored in the unlogged forest during 5 years. The population structure followed a bell-shaped curve. Mean annual diameter increments in both environments did not differ significantly between unlogged and logged areas. P. elata is a deciduous species that flowers at the end of the main dry season. The minimum reproduction and effective flowering diameters were, respectively, 32 and 37 cm. Fruit maturation took place during 7 months. With a minimum logging diameter of 90 cm, the recovery rate computed over a 30-year period was greater than 100%. Selective logging harvested only 12.1% of the total number of seed trees and had little influence on the species biological parameters. Securing sufficient regeneration as a post-logging action is probably the most important consideration for achieving long-term sustainability. Implications for the conservation status of the species are discussed at the regional level. [less ▲]

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See detailPericopsis elata (Harms) Meeuwen in Cameroon: Ecological Check-up of an Endangered Timber Species
Bourland, Nils ULg; Kouadio, Yao Lambert; Lejeune, Philippe ULg et al

Poster (2012, June 20)

Pericopsis elata (Fabaceae – assamela, afrormosia, kokrodua) is a high valued timber species of the moist semi deciduous African forests. Because of logging which started more than 50 years ago, it is ... [more ▼]

Pericopsis elata (Fabaceae – assamela, afrormosia, kokrodua) is a high valued timber species of the moist semi deciduous African forests. Because of logging which started more than 50 years ago, it is considered as threatened and included on both IUCN Red List and CITES Appendix II. Nevertheless, there is still little information available on the species ecology: essential biological parameters controlling its population dynamics remain unknown. Our study first aims at improving the knowledge of its main ecological parameters, then at assessing the impact of selective logging on its populations in a forest management unit in Cameroon (ca 120,000 ha). After inventorying the species (sampling rate of 1.2%), mortality and growth were assessed over continuous 5 and 2-year periods in unlogged and logged areas, respectively. Phenology was monitored in the unlogged forest during 5 years (leaf shedding and flushing, flowering, ripe and unripe fruiting). The population structure followed a bell-shaped curve. Mean annual diameter increments in both environments did not differ significantly between unlogged and logged areas (0.29±0.06 0.31±0.04 cm for unlogged and logged areas, respectively). P. elata is a deciduous species that flowers at the end of the main dry season (Marsh-April). The minimum reproduction and effective flowering diameters were, respectively, 32 and 37 cm. Fruit maturation took place during 7 months (the seed rain occurs in December-January), but all unripe fruits abort 3 years out of 5. With a minimum logging diameter of 90 cm, the recovery rate computed over a 30-year period was greater than 100%. Selective logging harvested only 12.1% of the total number of seed trees and had little influence on the species biological parameters. Securing sufficient regeneration as a post-logging action is probably the most important consideration for achieving long-term sustainability. [less ▲]

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See detailPhylogeography of african timber trees
Hardy, Olivier; Daïnou, Kasso ULg; Debout, Gabriel et al

Conference given outside the academic context (2012)

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See detailDéfinition du profil écologique de l'azobé, Lophira alata, une espèce ligneuse africaine de grande importance : synthèse bibliographique et perspectives pour des recherches futures
Biwole, Achille ULg; Bourland, Nils ULg; Daïnou, Kasso ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2012), 16(2), 217-228

Over two decades, labors made in order to promote sustainable management of African tropical forests are tackled to the lack of knowledge about this complex ecosystem. Ecological parameters of timber ... [more ▼]

Over two decades, labors made in order to promote sustainable management of African tropical forests are tackled to the lack of knowledge about this complex ecosystem. Ecological parameters of timber species are no more studied, this complicates long-term sustainable forest management. This literature review related to the ecology and silviculture of ekki, Lophira alata Banks ex C.F.Gaertn. (Ochnaceae), a main African timber species recorded as “vulnerable” in the IUCN Red List, will serve as a study’s case. The planned literature review reveals the doubt about its taxonomy, as well as the lack of understanding concerning its reproductive biology, growth conditions, population dynamics parameters, and the spatial distribution of its genetic diversity. The deficiency of knowledge about its ecological needs and the factors which have historically influenced its population dynamics explain why most silvicultural trails provide hazardous and uncertain results. Remedying these gaps in order to improve its ecological characterization and innovative silvicultural trails, would be a significant contribution to the sustainable management of its populations. [less ▲]

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See detailStructuration de la diversité génétique du genre Milicia: taxonomie, phylogéographie, dynamique des populations
Daïnou, Kasso ULg

Doctoral thesis (2012)

Characterizing population genetic structure using phylogeographic approach contributes to understanding of evolutionary processes that affect plant populations. The present study investigated how past ... [more ▼]

Characterizing population genetic structure using phylogeographic approach contributes to understanding of evolutionary processes that affect plant populations. The present study investigated how past environmental variations can shape the spatial genetic diversity of an African timber tree species, Milicia excelsa (Welw) C.C. Berg. Given that plant responses to disturbances are closely linked to life history traits, this research also aimed to describe relationships between the reproductive traits of M. excelsa and its population genetic structure. Phylogeographic analyses were performed throughout the range of M. excelsa using nuclear and chloroplastic markers. Ecological characterization was conducted for a single population located in south-East Cameroon. Since M. excelsa is similar to the other species of its genus, M. regia (A. Chev) C.C. Berg, we first performed a morphogenetic comparison of these two taxa. The results confirmed an important morphological similarity between the two species with very rare discriminating criteria. In fact Bayesian assignment methods and reproductive isolation patterns suggest the occurrence of interspecific hybridization, which appeared to be unidirectional: hybrids displayed the M. regia morphotype. Because M. regia is known to be more adapted to humid tropical forests, one may expect it to occur in the Congo basin zone. However, its range is restricted to the western part of West Africa while M. excelsa occurs from Guinea-Conakry to Zimbabwe. Interestingly, in the case of M. excelsa, Central and West African specimens had no shared haplotype. This result was unexpected because long gene dispersal distances were found in Cameroonian populations, as expected from the behaviours of the main dispersal animals we identified, the bat Eidolon helvum and the parrots Psittacus erithacus and Agapornis swindernianus. In general, despite the likelihood for long distance seed dispersal, distinct genetic clusters were identified over West and Central Africa and their location may support the forest refugia hypothesis. In addition a phylogeographical signal was detected in chloroplast DNA indicating a prolonged separation between West and Central Africa populations with an accumulation of new mutations. At a smaller spatial scale, patterns of genetic structure also seemed to be weakly influenced by divergent reproduction times among sympatric individuals. The level of genetic diversity in the study populations falls within the range of values calculated for other tropical tree species. If phylogeography helps to infer population history, it also requires ecological or biological information to confirm some uncertainties. Such detailed data were often lacking to completely interpret numerous of our results. The present study raised new questions and led to new perspectives for further investigation both in phylogeography and botany. [less ▲]

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See detailNature+ asbl - Rapport d'activités 2011
Federspiel, Michèle; Bourland, Nils ULg; Daïnou, Kasso ULg et al

Report (2012)

En 2011, Nature+ a rencontré ses missions, notamment : en mettant en oeuvre deux projets de foresterie communautaire financés par des bailleurs internationaux ; en participant à la gestion durable de près ... [more ▼]

En 2011, Nature+ a rencontré ses missions, notamment : en mettant en oeuvre deux projets de foresterie communautaire financés par des bailleurs internationaux ; en participant à la gestion durable de près de 2 millions d’hectares de forêts denses humides tropicales grâce à nos collaborations avec des sociétés forestières engagées dans les processus de certification FSC ; en accueillant dans nos divers projets 12 étudiants en fin de cursus universitaire ainsi que 8 doctorants. 7 universités différentes ont ainsi reçu un appui administratif, technique et scientifique de Nature+. [less ▲]

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See detailPhenological patterns in a natural population of a tropical timber tree species, Milicia excelsa (Moraceae): evidence of Isolation By Time and its interaction with feeding strategies of dispersers
Daïnou, Kasso ULg; Laurenty, Eric; Mahy, Grégory ULg et al

in American Journal of Botany (2012), 99(9), 1-11

Population genetic structuring over limited timescales is commonly viewed as a consequence of spatial constraints. Indirect approaches have recently revealed existence of reproductive isolation due to ... [more ▼]

Population genetic structuring over limited timescales is commonly viewed as a consequence of spatial constraints. Indirect approaches have recently revealed existence of reproductive isolation due to flowering time (the so-called isolation by time, IBT). Since phenological processes can be subject to selection, the persistence of flowering asynchrony may be due to opposing selective pressures during mating, dispersal and regeneration phases. Our study aimed to investigate phenology, fruit-handling by animals and their interaction, in a timber tree species, Milicia excelsa. We analyzed phenological data collected over a 6-year period on 69 genotyped trees in a Cameroonian natural rainforest complemented by data from germination trials and field observations of dispersers. Initiation of flowering correlated with variation in temperature and relative humidity, but was also affected by genetic factors: pairwise differences in flowering time between nearby individuals correlated with kinship coefficient, and earliness of flowering remained stable over time. A decrease in mean seed production per fruit with increasing flowering time suggests selection against late bloomers. However, germination rate was not affected by seed collection date, and the main seed disperser, the bat Eidolon helvum, seemed to increase in abundance at the end of the reproductive season, and preferred trees in open habitats where early and late bloomers are expected. The pairwise approach performs well to detecting IBT. The persistence of different mating pools in such a case may result from a trade-off between selective forces during the mating and seed dispersal processes. [less ▲]

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See detailIdentité et écologie des espèces forestières commerciales d'Afrique Centrale: le cas de Milicia spp.
Daïnou, Kasso ULg; Doucet, Jean-Louis ULg; Sinsin, Brice et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2012), 16

Le terme iroko regroupe les deux espèces du genre africain Milicia et désigne le bois qui en est dérivé. Malgré une importance économique reconnue depuis plus de deux siècles et une diminution sensible ... [more ▼]

Le terme iroko regroupe les deux espèces du genre africain Milicia et désigne le bois qui en est dérivé. Malgré une importance économique reconnue depuis plus de deux siècles et une diminution sensible des densités de population du fait de l'exploitation, les connaissances scientifiques utiles à la gestion durable de l'iroko font défaut, particulièrement en Afrique Centrale. L'existence même d'une spéciation au sein du genre Milicia mérite d'être revérifiée: les caractères utilisés pour séparer les deux taxons M. excelsa (Welw.) C.C. Berg et M. regia (A. Chev.) C.C. Berg sont peu consistants et une révision de ces traits distinctifs permettrait de réétudier le niveau de vulnérabilité des populations de Milicia spp., et donc de revoir les stratégies de gestion de ce groupe taxonomique. M. regia n'a fait l'objet que de rares études écologiques tandis que M. excelsa, plus largement distribuée, a retenu l'attention scientifique en Afrique de l'Ouest, dans une certaine mesure. Dans tous les cas, les traits d'histoire de vie conditionnant la diversité génétique et le taux de régénération naturelle méritent d'être identifiés ou mieux décrits. En particulier, les connaissances existantes sur les populations reproductrices, les facteurs régulant la floraison, les patrons de fructification et de dispersion des diaspores, ainsi que d'autres caractères qui amènent à décrire l'iroko comme un arbre pionnier (besoins en lumière, dormance des graines) devraient être mieux documentés. Enfin, la dynamique même des populations naturelles de juvéniles devra également être mieux caractérisée. En l'absence de données fines en écologie, la durabilité de nombreuses ressources ligneuses commerciales est tributaire d'actions sylvicoles, lesquelles peuvent être coûteuses et ne pas être garanties sur le long terme. [less ▲]

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See detailSylviculture in logging gaps of a Central African rainforest : first synthesis from tests with 11 timber tree species
Daïnou, Kasso ULg; Cerisier, Benjamin; Bourland, Nils ULg et al

in CIRAD Montpellier (Ed.) IUFRO International Conference , Research Priorities in Tropical Silviculture : Towards New Paradigms ?: Abstracts (2011, November 15)

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See detailSoil seed bank characteristics in Cameroonian rainforests and implications for post-logging recovery
Daïnou, Kasso ULg; Bauduin, Aline ULg; Bourland, Nils ULg et al

in Ecological Engineering (2011), 37(10), 1499-1506

The soil seed bank is considered as an important component for resilience of climacic vegetation. No investigation has ever been conducted in Central African rainforests regarding this topic. We studied ... [more ▼]

The soil seed bank is considered as an important component for resilience of climacic vegetation. No investigation has ever been conducted in Central African rainforests regarding this topic. We studied the soil seed bank characteristics in relation to the standing vegetation in three Cameroonian forest zones with different disturbance regimes. There was no significant difference between sites in terms of density of the seed bank. But dissimilarities of the floristic compositions between sites were high. Overall, seeds came from 43 species including three commercial tree species. Whereas the seedlings emerging from soil samples mostly came from weedy and short-lived pioneer species, climax species predominated in the extant vegetation, leading to a very weak similarity between soil seed flora and the surrounding vegetation. Canopy openness could significantly affect the species richness of soil seed stocks but not the seed density. These results show that the soil seed bank contribution to the resilience of mature tropical forests is low. In particular, very few timber tree species could benefit from soil seed stocks for their regeneration. Therefore, the development of enrichment techniques including use of the soil seed bank as a source of tree regeneration in such a context would be irrelevant. [less ▲]

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See detailSuivi des dispositifs de croissance implantés dans la concession forestière de Biliba (Compagnie Forestière des Abeilles, OLAM, Gabon)
Daïnou, Kasso ULg; Boubady, Armand; Doucet, Jean-Louis ULg

Report (2011)

Dans le cadre du projet WW113427 « Recherche appliquée et assistance technique aux exploitants forestiers – volet SHM » financé par la Coopération Néerlandaise, des dispositifs expérimentaux ont été ... [more ▼]

Dans le cadre du projet WW113427 « Recherche appliquée et assistance technique aux exploitants forestiers – volet SHM » financé par la Coopération Néerlandaise, des dispositifs expérimentaux ont été installés dans les concessions de la Société de la Haute Mondah (SHM) de fin 1998 à début 2002. Le présent document concerne le suivi du dispositif de croissance implanté dans la concession de Biliba (zone de Koumameyong-Ovan, Gabon) en octobre et novembre 2000. Une première campagne de mesure a été effectuée en 2001, soit une année après l’installation du dispositif. Les données obtenues ont été analysées par Doucet (2003). De nouvelles campagnes de mesure ont eu lieu en 2003, en 2006 et en 2008 et les données analysées par Doucet et Boubady (2004), Doucet et Boubady (2006) et Daïnou et al. (2008). Le remesurage le plus récent date de décembre 2010, ce qui permet d’avoir des résultats sur une période totale de 10 ans, durée d’observation exceptionnelle en forêt dense humide gabonaise. Depuis 2006, le financement des campagnes de mesurage est assuré par Nature Plus asbl, la Compagnie Forestière des Abeilles (CFA), GIB, OLAM, Gembloux Agro Bio-Tech et le groupe Millet. [less ▲]

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