Adaptive foraging of leaf‐cutter ants to spatiotemporal changes in resource availability in Neotropical savannas

1. Generalist herbivores feed on a wide and diverse set of species, but fine‐scale foraging patterns may be affected by the interplay between the quality, quantity and spatial distribution of host plants. 2. The foraging patterns of a prevalent Neotropical herbivore, the leaf‐cutter ant Atta laevigata, in the Brazilian Cerrado savannas were examined in order to determine if patterns observed are in concert with central‐place foraging predictions. 3. The results showed that A. laevigata acts as a polyphagous but highly selective herbivore, with ant attacks often resulting in partial defoliation of less‐preferred species and full defoliation of preferred ones. It was found, for the first time, that there is a strong and positive relationship between the relative attack frequency on plants from preferred species and foraging distance to the nest. This suggests a balance between the quality of plant resources harvested and costs involved in their transportation. It was also observed that colonies focused their harvest on preferred species in months with low availability of young leaves. Consequently, high herbivory rate was more frequent in plants attacked far away from the nest and in dry months. 4. These assessments highlight the fact that Atta colonies may become more selective as foraging distance to the nest increases and in response to fluctuations in the availability of palatable resources throughout the year. The results also show some dissimilarities in the foraging behaviours of A. laevigata when compared with other locations, suggesting that widely distributed herbivores may modify foraging strategies across their geographic range.     

Surveillance of Arboviruses in Primates and Sloths in the Atlantic Forest,Bahia, Brazil

From 2006 through 2014, we conducted seroepidemiological surveys on non-human primates and sloths to investigate the possible circulation of arboviruses in Bahia Atlantic Forest, Brazil. We collected a total of 196 samples from 103 Leontopithecus chrysomelas, 7 Sapajus xanthosternos, 22 Bradypus torquatus and 7 Bradypus variegatus. Serum samples were tested using neutralization test and hemagglutination inhibition test to detect total antibodies against 26 different arboviruses. The overall prevalence of arboviruses was 36.6% (51/139), with the genus Flavivirus having the highest prevalence (33.1%; 46/139), followed by Phlebovirus (5.0%; 7/139), Orthobunyavirus (4.3%; 6/139) and Alphavirus (0.7%; 1/139). Monotypic reactions suggest that the wild animals were exposed naturally to at least twelve arboviruses. Added results from the neutralization test, animals were exposed to thirteen arboviruses. Most of these viruses are maintained in transmission cycles independent of human hosts, although antibodies against dengue virus serotypes 1, 2 and 3 were found in this study. To our knowledge, this is the first study reporting exposure to arboviruses in L. chrysomelas, S. xanthosternos and B. torquatus. Our results also highlight that the Southern Bahia Atlantic Forest has a variety of vertebrate hosts and potential vectors, which may support the emergence or re-emergence of arboviruses, including those pathogenic to humans.     

Dominance–diversity relationships in ant communities differ with invasion

The relationship between levels of dominance and species richness is highly contentious, especially in ant communities. The dominance‐impoverishment rule states that high levels of dominance only occur in species‐poor communities, but there appear to be many cases of high levels of dominance in highly diverse communities. The extent to which dominant species limit local richness through competitive exclusion remains unclear, but such exclusion appears more apparent for non‐native rather than native dominant species. Here we perform the first global analysis of the relationship between behavioral dominance and species richness. We used data from 1,293 local assemblages of ground‐dwelling ants distributed across five continents to document the generality of the dominance‐impoverishment rule, and to identify the biotic and abiotic conditions under which it does and does not apply. We found that the behavioral dominance–diversity relationship varies greatly, and depends on whether dominant species are native or non‐native, whether dominance is considered as occurrence or relative abundance, and on variation in mean annual temperature. There were declines in diversity with increasing dominance in invaded communities, but diversity increased with increasing dominance in native communities. These patterns occur along the global temperature gradient. However, positive and negative relationships are strongest in the hottest sites. We also found that climate regulates the degree of behavioral dominance, but differently from how it shapes species richness. Our findings imply that, despite strong competitive interactions among ants, competitive exclusion is not a major driver of local richness in native ant communities. Although the dominance‐impoverishment rule applies to invaded communities, we propose an alternative dominance‐diversification rule for native communities.     

Stand dynamics modulate water cycling and mortality risk in droughted tropical forest

Transpiration from the Amazon rainforest generates an essential water source at a global and local scale. However, changes in rainforest function with climate change can disrupt this process, causing significant reductions in precipitation across Amazonia, and potentially at a global scale. We report the only study of forest transpiration following a long‐term (>10 year) experimental drought treatment in Amazonian forest. After 15 years of receiving half the normal rainfall, drought‐related tree mortality caused total forest transpiration to decrease by 30%. However, the surviving droughted trees maintained or increased transpiration because of reduced competition for water and increased light availability, which is consistent with increased growth rates. Consequently, the amount of water supplied as rainfall reaching the soil and directly recycled as transpiration increased to 100%. This value was 25% greater than for adjacent nondroughted forest. If these drought conditions were accompanied by a modest increase in temperature (e.g., 1.5°C), water demand would exceed supply, making the forest more prone to increased tree mortality.     

Seasonal variation of sound production in the Lusitanian toadfish Halobatrachus didactylus

Seasonal variation of sound production, which includes boatwhistles, grunts, croaks and double croaks, was studied in the Lusitanian toadfish Halobatrachus didactylus . Boatwhistles were emitted during the mating season in contrast with the other sound types, which were emitted all year round.     

Species Turnover and Vertical Partitioning of Ant Assemblages in the Brazilian Amazon: A Comparison of Forests and Savannas1

We measured beta diversity, or turnover in species composition, of ant assemblages inhabiting patches of forest and savanna (cerrado) near Alter do Chão, in the Brazilian Amazon. In addition, we assessed vertical partitioning of these assemblages by comparing the ground and lower vegetation strata within each habitat. Ants attracted to sardine baits were collected along transects in 39 savanna and 34 forest sites scattered over a 16 km × 16 km landscape. There were about twice as many species in the forest as in the savanna, and within both habitats, we collected more species on the ground than in the vegetation. Similar results were obtained when analyzing data at the level of individual transects, indicating that ant species richness is affected by both habitat and strata. About two‐thirds of the species recorded in the savanna were also found in the forest. Within both habitats, a large proportion of the species found in the least species‐rich stratum (vegetation) were also found in the richer one (ground). However, ordination analysis, using data from individual transects, revealed that different habitats and strata can be clearly discriminated from each other in terms of their ant species composition. Each habitat and stratum had a number of characteristic (indicator) species which, although generally not exclusive to that particular habitat and stratum, predominated there. Our findings indicate that habitat and strata specialization is an important factor governing the organization of ant communities in Amazonia.     

Clinical and cytokine profile evaluation in Northeast Brazilian psoriasis plaque-type patients

Objective and Design

Psoriasis is a common, enigmatic, and recurrent disease. The precise etiology and pathogenesis of psoriasis are still unclear. Psoriasis has been treated as an inflammatory disorder related to an underlying Th1/Th17-dominated immune response. Interleukins are involved in the development of psoriasis lesions through Th-17-associated inflammation. Th1 and Th17 cytokines are found in skin lesions and in the peripheral blood of psoriasis patients.We sought to analyze serum levels of IL-1-β, IL-8, IL-9, IL-27, IL-29, IL-35, IFN-γ, TNF and TGF-β in patients with psoriasis and healthy control volunteers.

Material

Blood samples were collected from fifty-three patients with psoriasis and thirty-five healthy controls.

Methods

Serum cytokines concentrations were determined using an enzyme-linked immunosorbent assay.

Results

Serum IL-8, IL-9, IL-27, IL-29 and TNF levels were statistically significant in psoriasis patients. Detectable serum IL-9 levels were found in 47 patients of the 53 in the psoriasis group.

Conclusions

Interleukins-8, 27, 29 and TNF levels measured in the serum of psoriasis patients were slightly elevated as compared to healthy controls in a weakly significant way. On the other hand, there were highly significant differences in IL-9 levels between the two groups.