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Major shifts in the availability of palatable plant resources are of key relevance to the ecology of leaf-cutting ants in human-modified landscapes. However, our knowledge is still limited regarding the ability of these ants to adjust their foraging strategy to dynamic environments. Here, we examine a set of forest stand attributes acting as modulating forces for the spatiotemporal architecture of foraging trail networks developed by Atta cephalotes L. ( Hymenoptera: Formicidae: Attini). During a 12-month period, we mapped the foraging systems of 12 colonies located in Atlantic forest patches with differing size, regeneration age, and abundance of pioneer plants, and examined the variation in five trail system attributes (number of trails, branching points, leaf sources, linear foraging distance, and trail complexity) in response to these patch-related variables. Both the month-to-month differences (depicted in annual trail maps) and the steadily accumulating number of trails, trail-branching points, leaf sources, and linear foraging distance illustrated the dynamic nature of spatial foraging and trail complexity. Most measures of trail architecture correlated positively with the number of pioneer trees across the secondary forest patches, but no effects from patch age and size were observed (except for number of leaf sources). Trail system complexity (measured as fractal dimension; Df index) varied from 1.114 to 1.277 along the 12 months through which ant foraging was monitored, with a marginal trend to increase with the abundance of pioneer stems. Our results suggest that some leaf-cutting ant species are able to generate highly flexible trail networks (via fine-tuned adjustment of foraging patterns), allowing them to profit from the continuous emergence/recruitment of palatable resources. [ABSTRACT FROM AUTHOR]

Urbanization causes species loss around the world, but its effects on phylogenetic diversity are poorly known in tropical forests. Using a patch-landscape approach in an urbanizing region of the Brazilian Atlantic Forest, we tested whether the increase in landscape urbanization reduces plant species density, phylogenetic richness and divergence, and increases the relatedness among co-occurring individuals and species. We assessed plant responses to urbanization in adult (diameter at breast height > 10 cm) and sapling communities (2.5-10 cm diameter) separately, as saplings are proxies of the future flora. We sampled 2860 woody plants belonging to 155 species in nine circular landscapes with urbanization level varying from 0% to 45%, and estimated the relatedness among the species that have increased and decreased in relative abundance in more urbanized landscapes (winner and losers, respectively). As expected, species density and phylogenetic richness decreased with the increase in urbanization. These responses were consistent for adult and sapling communities, suggesting a persistent loss of species and lineages in more urbanized landscapes. Contrary to our expectations, phylogenetic divergence and structure did not respond to urbanization, indicating that the more urbanized landscapes still retain much evolutionary history. However, because the relatedness among winners was greater than among losers, it is likely that the phylogenetic divergence gradually reduces and the relatedness increases, resulting in impoverished forests with uncertain ability to provide ecosystem services such as carbon storage and pest control. This environmental cost should be taken into account to align urban sprawl with biodiversity conservation. [ABSTRACT FROM AUTHOR]

The Brazilian Atlantic Forest is one of the most diverse environments, but it is also one of the most threatened areas in terms of loss of biodiversity and ecosystem services. Assessment of changes in the community structure during the recovery of forests can be performed using indicator organisms. Dung beetles perform several ecological functions and show high sensitivity to natural and anthropogenic environmental changes. This study aimed to investigate the effect of regeneration time of Atlantic Forest sites on structure of Scarabaeinae assemblages. We sampled dung beetles using ten baited pitfall traps per site, in six sites grouped into three classes of forest regeneration time (~30, ~60 and >80 years) in the southern Brazilian Atlantic Forest, during January 2015. A total of 520 individuals belonging to 16 species and nine genera of dung beetles were sampled. Rarefied species richness did not differ between sites with different regeneration times. Average species richness and abundance of Scarabaeinae was smaller in areas of shorter recovery time. True alpha diversity was higher in areas with intermediate recovery whereas Shannon diversity showed higher values in areas of shorter recovery. Approximately 29 % of the variation in abundance data of Scarabaeinae was explained by environmental variables, with one-third of this variation explained also by spatial predictors. External factors such as landscape management and farming practices in the surroundings must be taken into consideration in management plans and the management of natural areas for the recovery of biodiversity in the Atlantic Forest. These external factors can considerably affect the structure of communities and lead to scenarios of greater diversity in intermediate regeneration sites due to the heterogeneity of the landscape. [ABSTRACT FROM AUTHOR]

Trinomys is a very diverse mammalian genus of eastern Brazil, comprising ten species. Eight of them have remained in their original biome, the Atlantic Forest, while two others occupy the semi-arid Caatinga. One of the species from the Atlantic Forest, T. eliasi, also inhabits adjacent restingas, an open vegetation ecosystem on sandy sediments of marine origin. Here we assess the impact of colonization of very different environments on the rates of phenotypic change in Trinomys. Multivariate analyses showed that species that had remained in the Atlantic Forest maintained a strong cohesion in skull shape and size. By contrast, colonization of the Caatinga was associated with remarkable differentiation and a strong increase in the rates of phenotypic change, 7-17 times higher than in the Atlantic Forest. Trinomys eliasi from restinga differed from forest samples and other species by a recent change in morphology. Our findings showed that occupation of remarkably different ecosystems had a significant impact in the phenotypic evolution of Trinomys. [ABSTRACT FROM AUTHOR]

Seed dispersal may involve different vectors of dispersal in two or more sequential phases (i.e., diplochory). However, contributions of each phase to the overall seed dispersal effectiveness (SDE) are poorly understood and hard to evaluate due to post-dispersal processes that affect seed and seedling survival. We investigated the simultaneous bird (phase 1, in plant canopy) and ant (phase 2, on the floor) contributions to SDE with the ornithochoric shrub Erythroxylum ambiguum in a Brazilian Atlantic forest. Twelve species of birds fed on fruit and dispersed approximately 26 % of the seed crop. The remaining seed crop, 90 % of which contained viable seeds, fell to the ground beneath the parental plant. Ants either cleaned seeds in fruits or carried fallen fruit and seeds from bird feces to their nests. Although E. ambiguum has no adaptation for ant dispersal, ants were as quantitatively important as birds. Birds and ants equally increased germination rates compared to controls. However, birds deposited seeds farther from the parent, where seedling survival was higher (78 %) than it was beneath the parent (44 %), whereas ants carried seeds to their nests, where seedling survival was higher (83 %) than in controls away from their nests (63 %). Diplochory allowed a 42 % increase in SDE compared to dispersal in phase 1 alone. High lipid content in the fruit pulp of E. ambiguum may facilitate the inclusion of ants in a second step of dispersal after diaspores reach the floor. Ants can also buffer the dispersal of diplochorous plants against decreases in phase 1 dispersers. [ABSTRACT FROM AUTHOR]

Dung beetle community structures changes due to the effects of destruction, fragmentation, isolation and decrease in tropical forest area, and therefore are considered ecological indicators. In order to assess the influence of type of maize cultivated and associated maize management on dung beetle communities in Atlantic Forest fragments surrounded by conventional and transgenic maize were evaluated 40 Atlantic Forest fragments of different sizes, 20 surrounded by GM maize and 20 surrounded by conventional maize, in February 2013 and 2014 in Southern Brazil. After applying a sampling protocol in each fragment (10 pitfall traps baited with human feces or carrion exposed for 48 h), a total of 3454 individuals from 44 species were captured: 1142 individuals from 38 species in GM maize surrounded fragments, and 2312 from 42 species in conventional maize surrounded fragments. Differences in dung beetle communities were found between GM and conventional maize communities. As expected for fragmented areas, the covariance analysis showed a greater species richness in larger fragments under both conditions; however species richness was greater in fragments surrounded by conventional maize. Dung beetle structure in the forest fragments was explained by environmental variables, fragment area, spatial distance and also type of maize (transgenic or conventional) associated with maize management techniques. In Southern Brazil’s scenario, the use of GM maize combined with associated agricultural management may be accelerating the loss of diversity in Atlantic Forest areas, and consequently, important ecosystem services provided by dung beetles may be lost. [ABSTRACT FROM AUTHOR]

We studied the phenotypic variation of the Atlantic Forest passerine Xiphorhynchus fuscus (Aves: Dendrocolaptidae) with the broad aim of addressing whether the history and type of forest affected the evolution of endemic taxa. We also tested whether the different subspecies and genetic lineages of X. fuscus could be considered full species. We collected plumage and body size measurements and, in combination with genetic data, used multivariate tests to evaluate the working hypotheses. Our results, combined with previous biogeographic analyses, indicate that vicariant events have been important determinants in the evolution of phenotypic characters of X. fuscus, once genetic isolation was complete. Our analysis also suggests that forest heterogeneity and ecotones are important factors in the early evolution of Atlantic Forest taxa, perhaps via divergent selection. Forest instability during the Pleistocene was critical in the evolution of phenotypic traits. We confirm that the subspecies atlanticus should be considered a full species. Other lineages or populations are also phenotypically differentiated but we do not suggest considering them as full species. They share high levels of gene flow and are part of a continuous latitudinal cline of phenotypic variation. Our study suggests that not all the historic events in the Atlantic Forest that affected the evolution of genetic lineages also influenced the evolution of phenotypic characters in the same direction and intensity. Undoubtedly, natural selection played a major role in the evolution of Atlantic Forest organisms. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 1047-1066. [ABSTRACT FROM AUTHOR]

Contents [ABSTRACT FROM AUTHOR]

For butterflies, tolerance to the matrix may be an important criterion of habitat occurrence in fragmented landscapes. Here we examine the relative effects of habitat fragmentation and the surrounding agricultural matrix on the functional composition of fruit-feeding butterflies of the Atlantic rain forest in southeastern Brazil. Generalized linear models were used to detect the effects of landscape metrics on butterfly richness and abundance of the total assemblage and functional groups. Circular statistics were used to analyze the patterns of monthly abundance of the total assemblage and functional groups in the forest remnants and the surrounding matrices. In total, 650 butterflies representing 57 species were captured; species composition differed significantly between the forest fragments and the surrounding matrices. We recorded 22 forest specialists, 18 matrix specialists, 11 common species with matrix preference and six common species with forest preference. Forest connectivity favored the richness of forest specialists, while habitat fragmentation enhances the richness and abundance of matrix-tolerant species. Circular analysis revealed that forest specialists were more abundant in the rainy season while matrix-tolerant species proliferated in the dry season. Although maintaining connectivity of forest fragments may increase the mobility and dispersion of forest species, our results showed that landscape fragmentation modify butterfly assemblage by promoting an increase of matrix tolerant species with detriment of forest specialists. [ABSTRACT FROM AUTHOR]

Ants are a dominant faunal group in tropical forests, but their responses to human disturbances remain poorly investigated. Here we examine the relative effects of habitat fragmentation (fragment size and amount of forest cover retained in the surrounding landscape) and habitat structure (tree density and richness) on ant species and functional composition in the Atlantic forest of northeast Brazil. Our study was carried out in 19 fragments ranging in size from 10 to 3,500 ha. We recorded 146 ant species from 41 genera. Fragment size and tree density were the most important variables predicting species richness and functional diversity. Additionally, fragment area and tree density also explained the richness of a range of global functional groups (Cryptic Species, Specialists Predators and Tropical-climate Specialists) and Atlantic forest functional groups (Cryptic Predators, Cryptic Omnivores, Epigaeic Predators and Epigaeic Omnivores). Taxonomic composition was influenced by fragment area and tree richness, while functional composition responded to forest cover and tree density. Overall variation of global functional groups was also affected by tree richness. Our results suggest that specialist ants (especially cryptic species, specialist predators and climate specialists) are particularly sensitive to forest fragmentation. Such functional groups would make useful indicators of ant responses to forest fragmentation. [ABSTRACT FROM AUTHOR]

The feeding habits of understorey birds of two fragments of Atlantic Forest in southeast Brazil were studied, based on faecal content. The 434 samples examined contained 2535 items, principally consisting of invertebrates and fruit, of which 2286 (90.2%) could be identified in detail. Although there was no significant difference between the areas with respect to the occurrence of these two food categories in the diet, there were differences in the relative proportions of some of the invertebrate and plant taxa represented. Some birds that had been considered generalists appeared to have dietary specializations, indicating that existing knowledge of the trophic ecology of neotropical birds is inadequate. To eliminate this critical knowledge gap, it is recommended that studies be undertaken at community level together with examination of faecal samples, the latter being a low-cost, non-invasive, non-lethal technique. [ABSTRACT FROM AUTHOR]

Leaf-cutting ants ( Atta spp.) have become a topical issue in Neotropical ecology, particularly because they are reaching hyper-abundance due to escalating levels of fragmentation in recent years. Yet, despite intensive research on their role as dominant herbivores, there is still insufficient documentation on the impacts of their large, long-lived nests on plant assemblage structure and ecosystem functioning. Our study aimed at investigating the magnitude, nature, and spatial extent of nest influence by assessing 11 attributes of ant nest, canopy structure, light environment and sapling assemblage for 20 colonies in four plots along nest-understorey gradients in a large remnant of Atlantic forest. We also monitored the performance of seeds and seedlings of Chrysophyllum viride, an abundant shade-tolerant species. Previously unrecognized canopy gaps above ant nests (0.04–87.9 m2) occurred in 95% of all colonies surveyed. Overall, canopy openness and light availability at least doubled in ant nest plots compared with distant understorey plots. These drastic changes in the light environment paralleled those in plant assemblage: sapling density almost tripled (mean ± SE: 0.42 ± 0.1 saplings m−2) and sapling species richness doubled (0.16 ± 0.02 species m−2) in distant plots, as did shade-tolerant species. After a 1-year period, only 33 ± 15.6% of the seeds germinated and all seedlings died on nests, whereas seed germination reached 68 ± 5.1% in distant plots and 66.4 ± 7.6% of their seedlings survived after 12 months. Therefore, plot location was the most significant explanatory variable for predictable and conspicuous changes in the light environment and structure of sapling assemblages. Our findings greatly extend knowledge on the role played by leaf-cutting ants as ecosystem engineers by demonstrating that ant nest-mediated disturbance promotes environmental modifications in tens of meters around nests and is thus, strong enough to drive plant recruitment and consequently alter both the floristic and functional signature of plant assemblages. [ABSTRACT FROM AUTHOR]

Previous studies have shown that leaf-cutting ant populations benefit greatly from living in or near the edges of the Brazilian Atlantic forest. One of the mechanisms responsible for this rise in population density is an edge-mediated increase of pioneer plants, resulting in increased food availability for the ants (i.e., less bottom-up control). Here, we hypothesized that the release from natural enemies (i.e., less top-down control) may also contribute to the phenomenon. We investigated whether parasitism of phorid flies on leaf-cutting ants decreases in colonies located along the forest edge vs. the interior of a large tract of Atlantic forest in northeastern Brazil. For this, we assessed abundance and rates of oviposition attack by phorids in bimonthly intervals over a period of 1 year in 10 adult colonies of Atta cephalotes (L.) (Hymenoptera: Formicidae: Myrmicinae), five at the forest edge and five in the forest interior. The number of phorids attracted by ants at edge colonies was 40% lower than that at interior colonies. The temporal variation in phorid attraction was also significant, with approximately 35% fewer flies in the dry months as compared to the rainy months. As a result of lower phorid abundance, ant workers of edge colonies suffered three times fewer oviposition attacks than those of interior colonies. There was a tendency for fewer attacks during dry months, but the difference in the temporal variation was not significant. Our findings suggest that edge creation contributes to increased leaf-cutting ant abundance, not only via the attenuation of bottom-up forces, but also through an environmentally triggered depression of parasitoid abundance/efficiency, possibly because of adverse environmental conditions in edge habitats. [ABSTRACT FROM AUTHOR]