The City in the Tropics: Lizard Community Structure and Spatial Resource Use Along an Habitat Gradient of the Dahomey Gap (West Africa)

Abstract

Studies on habitat gradients are particularly interesting for the community ecology theory, but almost no investigation has been carried out on community structure of any vertebrate groups along gradients of habitat that were modified by humans in historical or prehistorical times, such as for instance the Dahomey Gap in West Africa. Here, we analyze the community structure of lizards in suburban Lomé (Togo) and in comparison with nearby savannah and forest sites, with a suite of statistical methods. Overall, we recorded 25 lizard species, with a heavy reduction in species richness from forest (18 taxa) to savannah (13) and suburbs (9). 24% of the species occurred in all habitat types, 40% exclusively in forest, and only two were exclusive of suburban habitats. Suburban habitat types were relatively homogeneous in terms of number of observed species (maximum number of taxa per habitat = 6). There were significant interspecific differences in both substratum type preferences and vertical spatial niche by species, but with no evidence of a nonrandom niche partitioning pattern, and hence with a competitively assembled community structure. There was a nonrandom “clustered” distribution of the various species along the available resource categories, thus indicating that species-specific preferences instead of community-driven mechanisms are more likely to explain the observed patterns. We concluded that lizard communities in tropical cities are (i) less species-rich than in the surrounding more natural habitats, (ii) usually clustered into specific habitat/substratum types (often artificial ones), and (iii) not assembled through competitive interactions.