No evidence for discovery-dominance tradeoffs in Pheidole (Hymenoptera: Formicidae) assemblages

Understanding ant community structure is of great interest among ant ecologists, since these insects stand out for their diversity, especially in the tropics, where they show high co-occurrence levels in many habitats. Discovery-dominance tradeoff is considered an important mechanism acting on ant community structure in many habitats, ensuring species co-occurrence by a temporal share of resources. We investigate the occurrence of this structuring mechanism in a Pheidole (Hymenoptera: Formicidae) assemblage at Atlantic Rainforest remains in south Brazil. If the discovery-dominance tradeoff is structuring this ant community, we expect that some species should be better to found food sources quickly, whereas other species arrive later and dominate food sources for their own consumption. We established 55 sampling locations at two sites, settling one sardine bait in each sampling unit to take note on the resource use by ants in a three-hour experiment. There was no distinction among species in terms of their ability to found or dominate food sources, which suggests that the discovery-dominance tradeoff is not structuring this assemblage. The low levels of aggression between ant species could avoid the establishment of dominance hierarchies, whereas territoriality could be acting to ensure resource partitioning. Also important is the fact that tradeoffs can vary with spatial scale, which can be assessed in further studies.

Ants in Burned and Unburned Areas in Campos Rupestres Ecosystem

Ground-dwelling ants have shown consistent resilience to fire in savanna environments. We carried out a study to investigate how ant community structure responds to fire in a harsh and fragile Cerrado ecosystem, the campos rupestres. We studied the change in the ant communities on a local scale subjected to fire in two rocky outcrop habitats at two different elevations (800m above sea level and 1300m a.s.l.). Pitfall trap samples were set at three different periods after a fire event: one, four, and ten months later. Overall, one hundred and fifteen ant species were collected. On a local scale, at the altitude of 800 m asl, no difference in richness and composition of the ant community was found between burned and control plots, whereas at 1300 m asl the burned areas showed higher richness and different ant composition in comparison to control areas. Differences were clear in the rainy period, four months after the fire. Ten months later, no difference between the richness of ant species in burned and unburned plots was found at higher altitudes, even though the plots showed distinct species composition. These data support the hypothesis that fire must be a structuring disturbance factor for some groups in the ant assemblages and indicate that ant community structure at higher elevations is somehow influenced by the recover of the campos rupestre vegetation.