Diversity and distribution of amphibian fauna within wetland ecosystems in greater Kampala City, Uganda

Abstract

Urbanisation is an important global driver of biodiversity change, negatively impacting some species groups whilst providing opportunities for others. Like most cities, Kampala is constantly expanding, thus altering most natural ecosystems including wetlands. The extent to which biodiversity is impacted by urbanisation depends on its intensity, the spatial scale, and the taxonomic group studied. Increasing urbanisation of greater Kampala areas comes with a cost to wetlands, resulting in direct impacts such as filling, drainage, and excavation, as well as indirect impacts caused by, for example, changes in hydrology, releases of pollutants, and introductions of non-native plants and animals. This generates great heterogeneity in habitats that affects relatively immobile animals, such as reptiles and amphibians (herpetofauna) as they become isolated at best and obliterated at worst. However, studies that evaluate effect of human activities on amphibians in the Kampala-metropolitan area are very scanty. This study focused on three wetlands that are in close proximity to the city center: Lubigi, Kinawataka and Kira. An urban-rural gradient was adopted, and sampling was done using Visual Encounter Survey technique between March and July, 2018. Three transects in each wetland were established and sampled twice. With exception of vegetation height and water depth, all the other habitat variables were visually estimated. Shannon-Weiner index was used to assess differences in species diversity among the wetlands. Relationship between amphibian species, wetland characteristics and intensity of land use types was determined using non-metric multidimensional Scaling (NMDS) ordination methods. In total, 1297 individuals belonging to 15 species were recorded by this study. Lubigi wetland had significantly higher proportion of amphibians, followed by Kiira and least Kinawataka. The urban wetlands had significantly lower numbers of amphibians compared to the peri-urban sites. Family Hyperolidae was the most dominant followed by Pyxicephalidae, Ptychadenidae, Bufonidae, and least was hrynobatrachidae. Four species that are considered nationally Data Deficient were recorded by this study. The different land-use types affected amphibian species abundance differently. Also, different species were not uniformly associated with the environmental variables assessed. These findings indicate that the remnant wetlands still support an array of amphibians and therefore there is need to consider herpetofauna in urban planning.