Herpetofaunal Diversity in a Dahomey Gap Savannah of Togo (West Africa): Effects of Seasons on the Populations of Amphibians and Reptiles

Abstract

The Dahomey Gap is a human-derived savannah zone, interspersed by patches of moist tropical forest, that separates the forest zone into two blocks, the Upper Guinean and the Lower Guinean forests. Community ecology aspects of amphibians and reptiles are still relatively unexplored in this ecological zone of West Africa. Here, the overall species richness and the variation of the diversity metrics (dominance, evenness) of a whole herpetofaunal community in Togo was studied, with emphasis on the effects of the seasons (wet and dry) on the population structure. Overall, we observed 998 amphibian individuals from 27 species: 148 individuals belonging to 11 species during the dry season and 849 individuals belonging to 25 species during the wet season. For reptiles, we observed 517 individuals belonging to 44 species: 323 individuals belonging to 41 species during the dry season and 194 individuals belonging to 28 species during the wet season. The analyses on the diversity metrics showed opposite patterns between amphibians and reptiles in each season. Indeed, the dry season rank–abundance curve was systematically higher in reptiles than in amphibians for each rank of abundance, while the opposite pattern occurred in the wet season rank–abundance curve. Singletons and doubletons were much more numerous in the reptiles. Concerning the diversity indices, the Dominance index was significantly higher in amphibians during the dry season than in all other pairwise comparisons, whereas the Shannon’s index was significantly lower in dry season amphibians and significantly higher in wet season reptiles. Evenness index was significantly lower in reptiles than in amphibians and the mean number of individuals was significantly higher in amphibians by wet season compared to dry season amphibians or reptiles during both seasons. The ecological implications of these data are discussed. Most species were of minor conservation concern.