Evidences that human disturbance simplify the ant fauna associated a Stachytarpheta glabra Cham. (Verbenaceae) compromising the benefits of ant-plant mutualism

Parasitism by Phorids on Leaf Cutter Ants Atta sexdens (Linnaeus, 1758) (Hymenoptera: Formicidae) in Natural and Agricultural Environments

The leaf cutter ant Atta sexdens (L.) (Hymenoptera:Formicidae) causes huge economic losses to agriculture in the Neotropics. In natural environments, parasitic flies of the Phoridae family are natural enemies of leaf cutter ants. Habitat modification is considered one of the main causes of species decline. In this study, we compare the occurrence of parasitic phorids on A. sexdens and the parasitism that they cause on colonies located in agricultural and natural habitats. Phorid flies were collected from trails, nest entrances, and cutting sites when they were hovering over workers of A. sexdens nests from natural vegetation, farmland, and Eucalyptus plantation areas. Simultaneously, workers from A. sexdens nests were collected from these environments, and the parasitism rates of phorids were determined. Ants were parasitized by Apocephalus attophilus, A. vicosae, Eibesfeldtphora bragancai, E. tonhascai, and Myrmosicarius grandicornis. The highest parasitism rate (3.54 ± 0.49%) was registered for nests from the Eucalyptus plantations. The rate of parasitism of nest from natural vegetation was 2.42 ± 0.40% and in the farmland was 1.91 ± 0.39%. The parasitism of each phorid genus varied according to habitat and month. Apocephalus attophilus had the highest parasitism in the three habitats and displayed biological characteristics that give it great potential as a biological control agent for A. sexdens. Eibesfeldtphora spp. had higher parasitism in a natural environment and M. grandicornis in agricultural environments. Apocephalus attophilus and M. grandicornis seemed able to occur in a wide variety of habitats that their hosts occupy, but the rate of parasitism by Eibesfeldtphora spp. was significantly lower in agricultural environments.

Ant assemblage (Hymenoptera: Formicidae) in three wind farms in the State of Paraná, Brazil

Abstract The transformation of natural habitats into areas destined to agriculture or projects of energy production has generated a growing concern about the impact on biological diversity. Thus, this study evaluated the diversity of ants in agroecosystems in the area of direct influence of three wind farms in the municipality of Marmeleiro, State of Paraná and examined the association of occurrences with sampling periods. To this end, four samplings were conducted in 2013, one per season. Pitfalls, Malaise trap and Net sweep were used. The assemblages were characterized and compared using richness and number of occurrences of ants. Chao 2 estimates were calculated and a comparison (rarefaction analysis) of the assemblages was performed. The association of the species with the samples was evaluated by a Principal Component Analysis (PCA). Altogether, there were 1,576 occurrences of ants, totaling 55 species. The obtained estimate indicated that richness may be up to 35% higher. Our study adds important information about richness and occurrence of ants in a region poorly analyzed for this group. Most of all, it presents a survey of species occurring in agricultural ecosystems that may serve as a parameter for future evaluations when wind farms are installed.

Canopy cover negatively affects arboreal ant species richness in a tropical open habitat

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.