Spatial Distribution of Acromyrmex balzani (Emery) (Hymenoptera: Formicidae: Attini) Nests Using Two Sampling Methods

Abstract

The spatial distribution (SD) of organisms is a key parameter in studies of population ecology. Among the methods to describe the SD of sessile organisms, sampling by way of plots and transects are widely used. The measurement of the distance between individuals (“nearest neighbor”) is a simple method that has not been employed in population studies with ants. This study aimed to evaluate the SD of ant mounds of Acromyrmex balzani (Emery, 1890), using both plot sampling and nearest neighbor methods in order to evaluate which method is more appropriate for determining SD of this species. In January 2013 we established 359 plots of 10 m2 on a fragment of grassland in Sergipe, Brazil. In the same study area 25 colonies were randomly selected and the distance of the closest neighbor colony was determined. In total, 153 ant mounds were sampled (plots) and the density was estimated in 975 × colonies ha-1. Colonies were clumped in the environment either by plot sampling (χ2 = 453.93; p < 0.05) as well as by the method of nearest neighbor (Ax= 0.67, t = -1.72, p < 0.05). The aggregation of A. balzani colonies found in this study may be due to habitat heterogeneity or relate to the strategy of colony foundation. We conclude that the use of the nearest neighbor method was as accurate as the plot sampling method, providing the same results with much lower sampling effort.

Keywords

• population ecology
• leaf-cutting ants
• nest density
• nearest neighbor