Fine-scale temporal and spatial dynamics of epigaeic ants in Fynbos: sampling implications

Abstract

Conservation and management strategies are dependent on reliable species richness information. Accurate species richness counts, especially for invertebrates, are almost impossible to obtain from sampling alone, due to the high costs and effort involved. Therefore, there is a great need to optimize sampling effort to gain maximum information from minimum sampling duration and intensity. Reliable species richness information is particularly critical for under-studied, high diversity regions, such as the Cape Floristic Region (CFR), where biodiversity is threatened by agricultural practices and urbanization. Ants (Formicidae) form an important part of the fauna of the CFR, especially as seed dispersers. This study investigated sampling effort options for maximizing ant species representivity in the region. The specific aims were to determine (i) whether a doubling in the sample duration significantly increased the number of species captured (ii) the effect of increased spatial versus temporal sampling effort on diversity estimates and (iii) the effect of adding an additional trapping method. Sampling was conducted at Elandsberg, Western Cape Province, from 20 February to 1 March 2004. Pitfall trapping was conducted in two five-day sessions and tuna-baits were used once. Species rarefaction curves were drawn and compared using EstimateS. A total of 42 species were captured and asymptotes to species richness were reached. Doubling of sample duration yielded no significant increase in species richness and was equally affected in terms of number of species as was doubling the sampling intensity. However, increasing the number of spatial replicates yielded a higher turnover in species. Baiting added no additional species to pitfall catches. Therefore, when sampling ant diversity in the CFR, investing sampling effort within seasons in spatial replication is likely to be more effective than increasing sampling duration.