Effects of bush encroachment on an assemblage of diurnal lizard species in central Namibia

Abstract

Bush encroachment is a serious environmental and economic problem in Namibia, but little is known about impacts on native reptile diversity. Area-confined visual surveys were used to examine a diurnal lizard assemblage in central Namibian commercial ranchlands. Surveys were conducted in plots of open savanna habitat and proximal bush-encroached habitat. The following four species comprised 97.5% of all lizard observations: Pedioplanis undata, Mabuya varia, M. striata, and Lygodactylus bradfieldi. Pedioplanis undata was terrestrial, and the remaining three species were largely arboreal in our study plots. Mabuya varia was found in all savanna plots but was absent from all bush-encroached plots. Two species ( P. undata and L. bradfieldi) were less abundant in bush-encroached plots. One species ( M. striata) was more abundant in bush-encroached plots than in open savanna plots. Arboreal lizards demonstrated an avoidance to invasive woody plant species. Decreased diversity of habitat structure in bush-encroached habitats appears to influence native savanna lizard assemblages. Our results are consistent with accumulating evidence suggesting that bush encroachment and its associated ecological impacts are reorganizing savanna ecosystems throughout southern Africa.