THERMAL DISRUPTION OF TRANSITIVE HIERARCHIES IN MEDITERRANEAN ANT COMMUNITIES

1. Ants are known to compete in transitive hierarchies, where the supe rior competitors behaviourally exclude subordinate species. Neverthele ss, in Mediterranean communities, where environmental factors show imp ortant daily and seasonal variations, the limited thermal tolerance of behaviourally dominant species compared with that of subordinates dis rupts the expected transitive hierarchies. 2. This thermal tolerance a llows a far greater dominance in the ecosystem by subordinate species than might be expected from their relative abundance and fighting abil ities. 3. In the studied areas, activity curves of dominants and subor dinates did not overlap because the latter were less temperature-limit ed and active during the day, while the former were more temperature-l imited and active during the afternoon and night periods. 4. The lower thermal limitation of subordinate activity not only increased their e xploitative ability, but also altered the outcome of interspecific int eractions at food resources, i.e. modified the interference hierarchy. 5. These temporal changes in the foraging abundance of species lead t o increasing diversity: more competing species may co exist as a resul t of changes in the environment that periodically reverse the order of competitive prevalence among the species.