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Cette etude a pour but d\'analyser les modeles de distribution spatiale des Acanthaceae, recoltees en Republique Democratique du Congo, au Rwanda et au Burundi et de comparer leur repartition spatiale avec les systemes phytogeographiques qui couvrent cette zone. Elle porte sur 9181 echantillons regroupes en 48 genres et 310 especes. Un systeme d\'information geographique a ete utilise pour realiser des cartes de distribution de chaque espece. La methode multi variee de classification, appuyee par deux indices de structure spatiale (equitabilite et fragmentation) a permis de stratifier la zone d\'etude afin de permettre une comparaison visuelle avec les systemes phytogeographiques definis par Robyns, White et Ndjele. On note une large distribution spatiale pour certaines especes sur l\'ensemble du territoire, alors que d\'autres sont infeodees a certains territoires phytogeographiques bien determines. Les savanes situees au Sud de l\'equateur contiennent des sites plus riches en Acanthaceae que celles situees au Nord. Les centres d\'endemisme Guineo-Congolais, Zambezien et Afromontagnard pourraient etre les sources de migration des taxons. Les Acanthaceae suivent relativement bien le systeme phytogeographique de White et sont utilisables en tant que bioindicatrices afin de rapprocher la distribution spatiale des communautes vegetales decrites par ce systeme. By means of 9181 samples representing 48 genus and 310 species, the spatial distribution models of the Acanthaceae family in Central Africa (Democratic Republic of Congo, Rwanda and Burundi) were analysed. Consequently, a comparison to existing phytogeographic systems for the study region was executed. Spatial distribution maps for each species were created using a geographic information system. Subdivision of the study area was realised using a multivariate classification analysis. Using two indices of spatial pattern (fragmentation, class size evenness), the classification result was compared to the phytogeographic zones defined by Robyns, White and Ndjele. While certain species showed a distribution throughout the study area, the presence of other species was found to be bound to one single phytogeographic territory in particular, or to a restricted number of them. The savannas situated in the southern part of the study area contained more Acanthaceae species than the zones situated north of the equator. The Guineo-Congolian, the Zambezian and the Afromontane centre of endemism are suggested to be the origins of taxon migration. Since it was observed that the spatial pattern of the Acanthaceae species corresponded up a certain extent to the phytogeographic system proposed by White, it can be concluded that the Acanthaceae could be used as bio-indicators to proxy the spatial distribution of plant communities as described by this system. Keywords : phytogeography, spatial analysis, Acanthaceae, Central Africa, district, sector. Sciences & Nature Vol. 5 (2) 2008: pp. 101-110 |
