The role of competition by dominants and temperature in the foraging of subordinate species in Mediterranean ant communities

In this paper we test the influence of temperature and interference competi tion by dominant species on the foraging of subordinate species in Mediterr anean ant communities. We have analyzed the changes in resource use by subo rdinate species in plots with different abundances of dominant ants, and in different periods of the day and the year, i.e., at different temperatures . The expected effects of competition by dominant species on foraging of su bordinates were only detected for two species in the number of baits occupi ed per day, and for one species in the number of foragers at pitfall traps. In all three cases, subordinate species were less represented at baits or in traps in plots with a high density of dominants than in plots with a med ium or low density of dominants. The number of workers per bait, and the fo raging efficiency of subordinate species did not differ in plots differing in dominant abundance. Daily activity rhythms and curves of temperature ver sus foraging activity of subordinate species were also similar in plots wit h different abundance of dominant species, indicating no effect of dominant s on the foraging times of subordinates. Instead, temperature had a conside rable effect on the foraging of subordinate species. A significant relation ship was found between maximum daily temperature and several variables rela ted to foraging (the number of foragers at pitfall traps, the number of bai ts occupied per day, and the number of workers per bait) of a number subord inate species, both in summer and autumn. These results suggest that the fo raging of subordinate ant species in open Mediterranean habitats is influen ced more by temperature than by competition of dominants, although an effec t of dominants on subordinates has been shown in a few cases. In ant commun ities living in these severe and variable environments, thermal tolerance r educes the importance of competition, and the mutual exclusion usually foun d between dominant and subordinate species appears to be the result of phys iological specialization to different temperature ranges.