The diversity and distribution of amphibian fauna in the Albertine Rift
MetadataShow full item record
This study was conducted in a variety of forest habitats in the Albertine Rift region. The study was conducted in the various sites between 15th November 2001 and 13th December 2003 with a major goal of assessing the status of amphibian fauna in the Albertine Rift. Amphibians were studied by a combination of sampling techniques, including time-constrained visual searching, pitfalls with drift fences, dip-netting, and opportunistic observations. Additional data were collated from literature so as to come up with as complete checklists of the study sites as possible. A total of 16,434 amphibian individuals were encountered during the 18 months of intensive sampling of the 15 forests in the Albertine Rift. Seventy-three species (61.3% of the overall Albertine Rift species richness of 119 species) were encountered during this study. Nyungwe NP was the richest site (35species) while Itwara and Echuya forest reserves (each with 19 secies) were the most species-poor sites). Based on literature there are 36 species considered to be endemic to the Albertine Rift with an additional four near-endemic species. However during the current study Nyungwe had the highest number of endemic species (14) while Virunga South had only two. In total only nineteen of the encountered species were endemic to the Albertine Rift and seventeen of the reported 36 endemics were never encountered during this study. This could have been due to the research being restricted largely to protected areas, comprising just a fraction of the total area coverby the Albertine Rift. Agricultural habitats were for example not sampled at all. It is therefore likely that additional species will be added with further sampling effort and habitat coverage. At a regional scale of the Albertine Rift, data were collated for 26 study sites for which comparable data could be obtained. A total of 119 species were recorded in the 26 study sites. This is approximately 19.2% of the total number of amphibians recorded for mainland Africa. Virunga North NP in DRC had 58 species and was the richest of the protected areas in the Albertine Rift while Pnvi Rwenzori (10spp) was the most species poor. The most widely distributed species was Afrana angolensis which was recorded in 24 out of the 26 sites, followed by Phrynobatrachus natalensis (22 sites), then Afrixalus fulvovittatus and Kassina senegalensis (20 sites each), Hyperolius kivuensis (19 sites), Hyperolius cinnamomeoventris, Hyperolius viridiflavus and Ptychadena mascareniensis (each in 17 sites), together with Bufo kisoloensis and Xenopus laevis (in 16 sites each). Pearson’s correlation coefficient indicated statistically significant relationships between species richness and the number of sampling hours (r = 0.65, n = 35, p = <0.001), species abundance and the number of sampling hours (r = 0.64, n = 35, p = <0.001) and species abundance and the number of sampling days (r = 0.57, n = 35, p = <0.001). Broad-scale ecological correlates with potential to affect species richness and abundance patterns of amphibians were studied in 37 sampling sites from 15 independent protected areas in the Albertine Rift, East Africa. There was a statistically significant relationship between percentage canopy cover and ecological distribution of species (r = 0.6317, n = 13, p = 0.012), indicating that areas with higher percentages of canopy covers had more species than those with lower percentage canopy covers. Ecological characteristics for each species were defined by a combination of habitat and microhabitat characteristics together with the time of activity of the species. The analyses showed that forests are important habitats for amphibians and play a very important role in explaining the distribution of amphibian fauna; about 63% of the species were classified either as forest specialists, forest ecotones species or forest interior/forest ecotones species. It was also indicated that wetlands and related macro/microhabitats stand out as very important habitats for amphibian fauna: more than 80% of the Albertine Rift species were recorded within wetlands. The vocalisation analyses resulted in the correction of identification of one species and assigning some calls to the correct species. This indeed shows that examination of anuran call patterns is a valuable tool for identification of taxa to species level. Analysis of vocalisations was able to assist in assigning the right identity of Phrynobatrachus mababiensis, which had been formerly misidentified as Phrynobatrachus acridoides. The amphibian fauna of the Albertine Rift is a transitional one, between the Eastern and Central African faunas, and contains elements of each. However the zoogeographic distribution of amphibian fauna showed that three endemic genera each represented by single species: - Laurentophryne parkeri, Callixalus pictus and Chrysobatrachus cupreonitens are exclusively endemic to the Albertine Rift. Zoogeographically the amphibian fauna of the Albertine Rift is also similar to that of other tropical fauna. Its affinities were found to basically lie closer to the West African rainforest fauna than to the East African Savannah.