Diversity and distribution of ant assemblages above and below ground in a West African forest�savannah mosaic (Lamto, C�te d�Ivoire)

Abstract

Habitat heterogeneity has a complex effect on ant species richness and community structure (both alpha- and beta-diversity). Savannahs and forests are thought to have distinct species assemblages, but studies comparing savannah�forest mosaics produced conflicting results, with savannah (the less complex ecosystem) poorer in species, equally rich, or richer than forest (the most complex habitat). We compared subterranean and above ground ant assemblages in savannah and forests of Lamto Reserve (C�te d�Ivoire) to examine how habitat heterogeneity and vertical stratification drive species composition and structure patterns. The Ants of the Leaf Litter (ALL) protocol and soil monolith were used to sample ants along 16 transects of 200 m in the three main habitats (gallery forest, forest islands, and savannah). In total, 138 species from 44 genera were collected. Forested habitats held assemblages that matched those found in savannah in terms of species density and richness; however, they differed in composition. Taxonomic structure varied among habitats, with Formicinae and Amblyoponinae prevailing in savannah, and Myrmicinae numerically dominant in forests. Ants were clearly vertically stratified. Subterranean assemblages had a less even distribution of occurrences among species as compared to above ground ones. The patterns observed agree with the heterogeneity-diversity theory relative to beta-diversity but not alpha-diversity, emphasizing the difficulty to generalize across continents about factors structuring ant assemblages. Our results support the need to conserve both forest and savannah to maintain biodiversity at landscape level in C�te d�Ivoire. © 2016 International Union for the Study of Social Insects (IUSSI)