Effect of a highway on ant (Hymenoptera: Formicidae) species composition and abundance, with a recommendation for roadside verge width

Abstract

Species composition and relative abundances of ground-dwelling ants at various distances from a major urban highway in South Africa were sampled using pitfall trapping. Diversity, richness and evenness indices indicated differences between ant assemblages, with samples near to the highway (<4 m) having the highest species diversity, and farthest ones (32 m) having the lowest. As measured environmental variables did not explain much of the variation in the species spatial pattern, it appears that the ants were influenced mostly by interspecific competition and/or distribution of food resources, especially road kills. Pheidole megacephala was highly dominant at all sites and was negatively associated with several other species. This and other dominant species appeared to be influencing the abundance of the rarer ones. Dominance and high abundances of species in the genera Pheidole, Monomorium, Tetramorium and Paratrechina, along with the occurrence of certain grasses, indicated that the whole sampling area was disturbed. In a suburban setting, a narrow roadside verge (<4m) is probably adequate. However, for maximum diversity in rural areas, roadsides should be as wide as possible and also rich and heterogenous in native vegetation.