Carla R Ribas

The simplification of native habitats leads to biodiversity decline in tropical terrestrial ecosystems. We evaluated how conversion of three types of native Cerrado vegetation (open grassland, typical savanna, and woodland savanna) to two human-managed land uses (Eucalyptus plantations and pastures) affects ant richness and composition in arboreal, epigaeic, and hypogaeic ant communities. We also sampled vegetation and soil characteristics to determine which specific features could be driving differences in ant communities with land use conversion. In general, biodiversity was negatively affected by conversion to Eucalyptus plantations and pastures regardless of vegetation type. But these impacts do not act in the same way in each ant strata or vegetation type. Grass and herbaceous cover was the most important environmental variable correlated with diversity in open grassland and plant richness and litter diversity were the most important environmental variables for ant species in typical and woodland savannas. Our results indicate that expanding Eucalyptus plantations may have stronger negative impacts from conversion of open vegetation types while pasture implementation may have stronger negative effects if implemented in closed vegetation types. Thus, we show the need of protection of the diversity of all native vegetation found in the Brazilian Cerrado (from open to forested habitats).

"This study aimed to determine how the richness and composition of ant species behaves with changes in the recovery process of a gully erosion. The study area has 0.9 hectares subdivided into three sections called sector: “A”, “B” and “C”. For the definition of the sectors, erosive and natural restoring were taken as the base level of activity. Four transects were laid systematically throughout the area and surrounding compound with forest and grassland. Each transect had three “pitfall trap” ten meters apart
from each other, with catches of ants were held in rainy and dry seasons. Analysis of variance was applied to compare the number of ant species per plot captured and Scott-Knott test 5% for comparison of means. To verify the similarity of species between environments it was performed an analysis of similarity (ANOSIM) and ordering of environments a “Nonmetric Multidimensional Scaling” (NMDS). We captured 74 species of ants inside and around the gully erosion. The more degraded environment and initial stage of regeneration, showed greater richness of ant species. The composition of ant species was different between the recovery environments and around. The parameters of ant communities analyzed, richness and composition species were influenced by the regeneration of the area, indicating that ants can be used as bioindicators of gullies recovery."

differences in habitat complexity and the natural history of the Australian and South American ant faunas. We also observed an increase for arboreal-ant activity density and species richness with increased time after the arboreal pitfall installation. Probably, arboreal ants avoid strange objects (pitfalls) in the tree in the early phase, and then, over time, they might become familiarized with the pitfall and start to fall into the trap. We term this process the familiarization effect, referring to the time that the ants require to become familiar with the trap, which was about 4–7 days after the installation. These results suggest that in closed-forest habitats, precautions to avoid a digging-in effect may be unnecessary for epigaeic samples, but that it is best to wait at least 5 days after an arboreal pitfall is installed to begin sampling ants.

We tested the hypothesis of a negative relationship between vegetation characteristics and ant species richness in a Brazilian open vegetation habitat, called candeial. We set up arboreal pitfalls to sample arboreal ants and measured the following environmental variables, which were used as surrogate of environmental heterogeneity: tree richness, tree density, tree height, circumference at the base of the plants, and canopy cover. Only canopy cover had a negative effect on the arboreal ant species richness. Vegetation characteristics and plant species composition are probably homogeneous in candeial, which explains the lack of relationship between other environmental variables and ant richness. Open vegetation habitats harbor a large number of opportunistic and generalist species, besides specialist ants from habitats with high temperatures. An increase in canopy cover decreases sunlight incidence and may cause local microclimatic differences, which negatively affect the species richness of specialist ants from open areas. Canopy cover regulates the richness of arboreal ants in open areas, since only few ant species are able to colonize sites with dense vegetation; most species are present in sites with high temperature and luminosity. Within open vegetation habitats the relationship between vegetation characteristics and species richness seems to be the opposite from closed vegetation areas, like forests. A cobertura de dossel afeta negativamente a riqueza de formigas arborícolas em um hábitat tropical aberto Resumo Nós testamos a hipótese de que há uma relação negativa entre as características da vegetação e a riqueza de espécies de formigas em habitats abertos como o candeial. Para isto, nós instalamos pitfalls arborícolas para a captura de formigas e mensuramos as seguintes variáveis ambientais: riqueza de árvores, densidade de árvores, altura de árvores, circunferência basal das plantas e cobertura de dossel. Somente a cobertura de dossel apresentou efeito negativo na riqueza de formigas arborícolas. Provavelmente, as características da vegetação e a composição de espécies de plantas são mais homogêneas no candeial, o que explica a ausência de relação entre a riqueza de formigas e as outras variáveis ambientais. Formações abertas abrigam um grande número de espécies oportunistas e generalistas, além de formigas especialistas de climas quentes. O aumento na cobertura de dossel diminui a incidência solar o que pode causar diferenças microclimáticas que afetam negativamente as espécies de formigas especialistas de hábitats abertos. A cobertura de dossel regula a riqueza de espécies de formigas arborícolas em áreas abertas e poucas espécies nestes locais estão aptas a colonizar locais com a vegetação densa. Assim, a maioria das espécies estão presentes em locais com alta temperatura e luminosidade. Em outras palavras, em hábitats de vegetação aberta a relação entre características da vegetação e a riqueza de espécies pode ser oposta em comparação ao que é encontrado em áreas que apresentam a vegetação mais fechada, como florestas. Palavras-chave: heterogeneidade ambiental, microclima, características da vegetação, partição hierárquica, candeia.

We analyzedarthropod community structure and composition among different anthropogenic
systems. The study was conducted in areas of secondary forest (control system),  Eucalyptusplantation
and pasture, where we sampled arthropodsusing pitfall traps. The systems did not differ in mean richness
and mean abundance of arthropods, however, eucalyptus presented the highest total richness. The systems
supported different arthropod communities in relation to structure and species composition. Pasture was
the most simplified and different system in comparison to the others, probably because it is more open
and presents low complexity. Our results demonstrate that different anthropogenic  systems exhibit
communities that reflect itscharacteristics, corroborating the evidence that human impacts are capable of
changing community composition and structure. Our study serves to understand arthropod response in
face of environmental disturbance, selecting indicator morphospecies and orders of arthropods for
different anthropogenic systems and providing valid information for the development of conservation
strategies.