Systématique, phytogéographie et utilisation de quelques Fabaceae-Caesalpinioideae Clade des Mimosoideae du Cameroun : cas des genres Albizia, Parkia et Tetrapleura

Abstract

Cameroon has one of the highest biological diversity in tropical Africa, in terms of specificity, ecosystems and genetic resources. In terms of species richness, has one of the best- known flora in Africa in terms of the collection, however, taxonomic knowledge remains limited, as almost half of the 225 families in the “flore du Cameroon” series are yet to be described. This is the case for the Fabaceae-Caesalpinioideae subfamily and the Mimosoideae Clade, for which there is a lack of data on diversity, floristic richness, geographical distribution and uses. Thus, a study was carried out to contribute to the knowledge of this species in Cameroon. The general objective was to do enrich the floristic diversity of three genera Albizia, Parkia and Tetrapleura (Fabaceae-Caesalpinioideae Clade des Mimosoideae) in Cameroon. For studies on systematics, standard analysis methods were applied, consisting of observation, with or without binocular magnifying glass of botanical samples of the genera present in the Cameroon National Herbarium (YA), those collected in the field and samples from virtual herbaria available on the Internet. For the biogeographical studies, IGN maps at a scale of 1:200,000 were produced using ArcMap arcgis 10.8 software, with grids of 11 (one degree square), followed by analyses and interpretations based on the phytogeographical map of Cameroon and the map representing the ecosystems and main natural habitats. Ethnobotanical data collection was based on available plant material and survey frames. The data was collected over a two-year period from 2019 to 2021. The surveys consisted of semi-structured interviews of focus groups and interviews with isolated individuals, on a sample 173 people, belonging to the main ethnic groups (Bamiléké, Beti, Peul, Sawa) in Cameroon, represented in these two largest cities (Yaoundé and Douala). From this study, 19 taxa at species rank including 15 Albizia spp, 3 Parkia spp and one Tetrapleura sp were described and illustrated in Cameroon. A dichotomous identification key was proposed to recognise the three genera and their species. The Guineo-Congolese region and the transition zone between the Sudanese and Guineo-Congolese regions are recognised as the main centres of diversity for these three genera. Seven species (A. adianthifolia, A. laurentii, A. lebbeck, A. zygia ; P. bicolor and P. biglobosa ; T. tetraptera) are used in Cameroon for their ethnobotanical values are divided into five main groups of uses (medicinal, food, magico- religious-cultural, cosmetics, timber). Some species, such as Albizia lebbeck, Albizia zygia, Parkia biglobosa and Tetrapleura tetraptera, have multiple uses. Emphasis was placed on Tetrapleura tetraptera as a priority non-timber forest product, and its contribution to improving people's living conditions was determined. A value chain for this resource was proposed.