Temporal Turnover of Species Maintains Ant Diversity but Transforms Species Assemblage Recovering from Fire Disturbance

Abstract

The rupestrian complex is a montane transitional vegetation type between the Brazilian Savanna (‘Cerrado’) and the Atlantic Forest, frequently threatened by human activities. In this study, we evaluated the recovery to fire disturbance of ant fauna in an environment evolved under fire regime. We confirmed that the ant diversity recovers quickly after the fire. However, our results show that ant assemblage in burned areas presented greater ant’s foraging activity, here detected as higher abundance. The ant composition changed over time, being that species turnover lead to a strikingly different species composition comparing burned to unburned areas after 16 months of recovering. In fact, both areas changed their ant composition through species turnover, but we believe that the mechanisms that act in species turnover are different in each area. Along time, in burned areas the fauna maintained a constant species diversity but dramatically changed species assemblage due to appearance of several species not found in the unburned area.

Monitoring Effect of Fire on Ant Assemblages in Brazilian Rupestrian Grasslands: Contrasting Effects on Ground and Arboreal Fauna

“…Second, the change in relative abundances of the four most frequent species on the ground was much greater in the burnt than unburnt area ( Pheidole reflexans — (mean ± SD) burnt: 17.20 ± 31.56, unburnt: 7.66 ± 10.52; Camponotus crassus —burnt: 5.30 ± 8.40, unburnt: 2.00 ± 1.10; Camponotus rufipes —burnt: 8.23 ± 15.69, unburnt: 3.60 ± 2.52; Pheidole sp2—burnt: 10.65 ± 16.39, unburnt: 1.66 ± 0.81). Strong effects of fire on ant composition (i.e., changes over time) were also reported in two other studies of fire ants in rupestrian grasslands [ 15 , 16 ].…”

“…The absence of fire effects on cumulative species richness can be explained by several factors. First, based on the long geological time that ants have inhabited fire-prone environments such as the Brazilian savanna [ 12 , 14 , 36 ] and rupestrian grasslands [ 15 , 16 ], we expect these insects to be highly resistant and resilient to fire. Areas with shorter vegetation stature (e.g., rupestrian grasslands) are dominated by ants that nest in the soil, protected from direct effects of fire.…”

“…Each arboreal pitfall trap was tied to the trunk of the shrub/tree closest to the ground pitfall at approximately 1.20 m height. The pitfalls were made from 20 mL plastic containers with 3 cm diameter, and stayed open in the field for 96 h [ 15 ]. Ants were sampled monthly between October 2010 and October 2012, totaling 960 samples per grid/area.…”

“…With respect to the impacts of fire, ants are one of the best-studied animal taxa [ 12 , 13 , 14 , 15 , 16 ]. In fire-prone habitats—such as the tropical savannas of Australia, Africa, and South America—the natural regime (higher frequency and lower intensity) can increase the structural diversity of vegetation, generating long-term positive effects on ant diversity [ 14 , 17 , 18 ].…”

“…On the other hand, forest studies have shown strong and negative consequences of fire (e.g., fire from human activities) on ant diversity at all spatial and temporal scales [ 19 , 20 , 21 ]. With regards to the rupestrian grasslands, there is little information about effects of fire on ant communities (but see [ 15 , 16 ]). Our expectation is that ant community responses to fire are likely more similar to those typical of savanna than to forest habitats [ 16 ], as rupestrian grasslands possess floristic and landscape features that are more similar to Brazilian savanna than Atlantic forest [ 3 ].…”