Some Ecological Characteristics of the Ants of a Desert-Shrub Community in Southeastern Arizona

Abstract

Ants were studied principally by analysis of collections at 66 stations on a 30.3-m grid baited with honey solution and peanut butter. Twenty-three species were collected, which is an exceptionally diverse ant fauna for a small area. Analyses suggest there are several bases for coexistence of these species: (1) Mean body weights of most species are significantly different from each other, and always so within three general feeding categories (seeds; nectar, honeydew and insects; omnivorous). The mean ratio of dry weight of workers of pairs of nearest species was 1.66 within feeding categories and 1.28 between categories. (2) Forage items showed some distinctiveness of food habits among species. (3) Some species were clearly diurnal and others nocturnal in August. (4) Only four species were active up in shrubs in the daytime, and they had their peak numbers in different months or different species of shrubs. (5) Hierarchical classification of stations by species characteristics showed some patterns of distribution of groups of sites according to topography and unknown factors. Other data are given on importance curves, enrichment of species collected with time and space sampled1, species-area relationship, species interactions, and patterns of daily dispersal of workers. Introduction Ants are often assumed to be important components of ecosystems, and in a few cases their importance has been specifically documented, e.g., in terms of energy flow (Golley and Gentry, 1964), modification of soil chemistry and plant distribution (Gentry and Stiritz, 1972), and effects on microsuccession and composition of vegetation (Talbot, 1953; Tevis, 1958). This study concerns a particularly diverse fauna of 23 species of ants within a creosote bush desert community in southeastern Arizona. Simple techniques were used to determine the general ecological characteristics of the ant fauna of the study site, as a prelude to a more extensive study. In particular, ants were collected at bait stations, intensively over a short period of time in August 1972. The collections provided information on species diversity and equitability of the fauna, importance curves, body sizes of species, patterns of diel activity and foraging, patterns of distribution of species in space, and interactions of species. These data, together with information on food habits and activity through a year's time, provide a good initial understanding of the possible bases of coexistence of the ant species of the community. Since the fieldwork was done, several authors have shown that the use of baits, in spite of their artificiality, is a productive way of determining some aspects of ant ecology (Pressick, 1972; Hunt, 1973; Culver, 1974). 33 This content downloaded from 157.55.39.111 on Sat, 17 Sep 2016 06:12:02 UTC All use subject to http://about.jstor.org/terms 34 The American Midland Naturalist 98(1)