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

Abstract

In this paper we test the influence of temperature and interference competition by dominant species on the foraging of subordinate species in Mediterranean ant communities. We have analyzed the changes in resource use by subordinate 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 subordinates were only detected for two species in the number of baits occupied 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 medium or low density of dominants. The number of workers per bait, and the foraging efficiency of subordinate species did not differ in plots differing in dominant abundance. Daily activity rhythms and curves of temperature versus foraging activity of subordinate species were also similar in plots with different abundance of dominant species, indicating no effect of dominants on the foraging times of subordinates. Instead, temperature had a considerable effect on the foraging of subordinate species. A significant relationship was found between maximum daily temperature and several variables related to foraging (the number of foragers at pitfall traps, the number of baits occupied per day, and the number of workers per bait) of a number subordinate species, both in summer and autumn. These results suggest that the foraging of subordinate ant species in open Mediterranean habitats is influenced more by temperature than by competition of dominants, although an effect of dominants on subordinates has been shown in a few cases. In ant communities living in these severe and variable environments, thermal tolerance reduces the importance of competition, and the mutual exclusion usually found between dominant and subordinate species appears to be the result of physiological specialization to different temperature ranges.

Subtidal macrozoobenthos communities from northern Chile during and post El Niño 1997–1998

“…Results showing higher species diversity when species co-occurrence patterns are negative seem to be counterintuitive, mainly because competitive interactions that cause negative co-occurrence patterns are assumed to decrease diversity (Huston 1979;McAuliffe 1984;Cerdá et al 1998;Weiher and Keddy 2001). However, while it is feasible to think that species strongly compete during EN, it is also possible that sampling stations across the study area are being occupied by certain groups of non-competing species that can coexist.…”

A proactive–reactive syndrome affects group success in an ant species

“…senilis is a relatively thermophilic species that uses group recruitment at temperatures of up to 45 °C when exploiting valuable food resources in the field (Cerdá et al 1998b); this temperature is very close to its critical thermal maximum (Cerdá et al 1998a). In the risk-taking trial, proactive colonies continued foraging even at extreme temperatures (of up to 57 °C).…”

The trade‐off between thermal tolerance and behavioural dominance in a subtropical South American ant community

“…loss of biomass to herbivores) ± are the basis for trade-o s in plants and thus for functional types. For ants, varying microclimate, particularly temperature, is one environmental challenge that has important consequences for ant community structure (Andersen 1995;Cerda , Retana & Manzaneda 1998). For example, changes in ant species composition and abundance due to alteration of habitat structure (Andersen 1991;Punttila et al 1994;Perfecto & Vandermeer 1996) are often ultimately tied to microclimatic changes.…”