Habitat fragmentation,EFN‐bearing trees and ant communities: Ecological cascades in Atlantic Forest of northeastern Brazil

Habitat fragmentation has a marked impact on the functional composition of tropical forest tree assemblages, and such change is likely to cascade through other trophic levels. Here, we investigate how habitat fragmentation affects extrafloral nectary (EFN)‐bearing plants and ant functional groups known to attend EFNs in a fragmented landscape of the Atlantic Forest. Extrafloral nectary‐bearing trees were identified in 50 0.1‐ha plots located in forest fragments, edge and interior patches. Ants were surveyed in 30 1‐m² litter samples in each of 17 forest fragments and in forest interior. Extrafloral nectary‐bearing plants accounted for 19.9% of individuals and 10.5% of species and included both pioneer and shade‐tolerant species similarly rich in the three habitat types. However, shade‐tolerant individuals accounted for >80% of EFN‐bearing plants in forest interior, compared with 2% in forest edge and 29% in fragments. Forest edge and fragment plots had a third fewer EFN‐bearing individuals and species compared with forest interior. This appeared to have important implications for local ant communities as the density of EFN‐bearing trees was the most important variable explaining the species richness of arboreal dominant ants. Our results show that plant loser–winner replacements promoted by forest fragmentation can cascade through higher trophic levels, with implications for forest dynamics and biodiversity conservation.     

Forest fragmentation drives Atlantic forest of northeastern Brazil to biotic homogenization

Aim To examine whether the tree flora of the Atlantic forest of northeastern Brazil has experienced detectable taxonomic homogenization via the proliferation of native pioneer species in response to habitat loss and fragmentation. Location Biotic homogenization (BH) was examined across the Atlantic forest of northeast Brazil, i.e. a 56,000 km² piece of tropical forest and a distinct centre of species endemism in South America. Methods We assessed a dataset consisting of 5122 tree records and compared the similarity of tree floras from 12 semi‐natural sub‐regions of the Atlantic forest between two time periods: pre‐1980 (plant records between 1902 and 1980), and post‐1980 (between 1981 and 2006). To understand the mechanisms leading to BH (1) tree floras were ordered (via non‐metric multidimensional scaling – NMDS) by date (pre/post 1980) based on species occurrence and frequency, (2) NMDS axes were regressed against the proportion of those species that increased their occurrence post‐1980 (i.e. the winner species), and (3) patterns of geographic distribution and frequency of particular life‐history traits were examined across winner species and a control group. Results Tree floras across the Atlantic forest became c. 20–40% more similar to each other post‐1980, but patterns of species similarity were also influenced by between‐plot geographical distance. NMDS ordination clearly segregated pre‐ and post‐1980 floras with a clear signal of floristic convergence. Furthermore, winner tree species were largely composed of short‐lived and small‐seeded pioneer species that exhibit wide geographic distributions. Main conclusions Our results suggest that tropical forest biotas are susceptible to taxonomic homogenization (i.e. increasing levels of similarity) in the context of severe human‐disturbance via the proliferation of particular groups of native species comprised mainly by ecologically‐plastic, generalist species. We are thus extending the concept of homogenization to address and highlight a pervasive biological shift in the structure of tropical forest communities currently taking place across hyper‐fragmented landscapes.     

Pollination Biology of Distylous Rubiaceae in the Atlantic Rain Forest, SE Brazil

Abstract: Data on pollination biology constitute important clues for the comprehension of pollen flow and genetic differentiation in plant populations. Pollinator type, availability and behaviour may modify morphological and mating patterns in populations of typically distylous species. This study investigates the pollination biology of four distylous species of Rubiaceae in the Atlantic rain forest, SE Brazil. Data on flowering phenology, floral lifespan, stigmatic receptivity, pollen availability, nectar volume and concentration, and pollinator activity were collected. The species studied flower sequentially throughout the wet season, and produce terminal inflorescences which bear small, tubular, diurnal, nectariferous flowers. Despite these similarities, some of the species studied are pollinated by different groups of pollinators, probably due to their distribution, availability of flowers and corolla length. On the other hand, pollinator specificity does not seem to be so important for distylous species. Long mouthparts, like those of most of the recorded pollinators, may reach lower sexual organs and, together with the self- and intramorph-incompatibilities observed, be sufficient to perform legitimate pollination and maintain levels of intermorph mating.     

Host-ectoparasite specificity in a small mammal community in an area of Atlantic Rain Forest (Ilha Grande, State of Rio de Janeiro), Southeastern Brazil

The analyses of the ectoparasite species associated with a small mammal community on Ilha Grande, a coastal island in southern of the state of Rio de Janeiro, Brazil, evaluated the level of host-ectoparasite specificity. Was used the Jaccard index for qualitative data to analyse the similarity. The lowest value of similarity occurred between Proechimys iheringi and Marmosops incanus and between Sciurus aestuans and Nectomys squamipes (Cj=0.08) and the highest between P. iheringi and Oxymycterus sp. (Cj=0.33). This index showed a low value of similarity across the ectoparasite community. The only exception from this pattern of high host specificity occurred with P. iheringi and Oxymycterus sp., which shared five species of ectoparasites. The similarity values, for most of the cases, is smaller than 0.2.     

Use of Sentinel 2 imagery to estimate vegetation height in fragments of Atlantic Forest

Information on vegetation height can be used in a variety of applications, but the high cost to obtain it in large areas using field sampling and the latest remote sensing technologies is still a barrier for low-income countries and organizations. In an attempt to overcome these limitations, we explored the possibility to estimate vegetation height in fragments of Atlantic Forest (São Paulo - Brazil) based on Sentinel 2 imagery, using LiDAR (Light Detection And Ranging) and field data as reference. The initial results showed that only wet season images appear to be related to the vegetation height, especially band 5 (red-edge) and related vegetation indices (VIs). Predictions made with Sentinel 2 and LiDAR data showed that vegetation height can be estimated with a root mean square error (RMSE) close to 3 m, with simple linear models outperforming random forest algorithms. It's also shown in a variety of validation tests, that although better results are obtained if the models are applied to the same images they were trained in, they are still able to reasonably predict vegetation height when applied to other images and locations if the right predictive variables are used. The results agree with recent studies made in other biomes and show that Sentinel 2 imagery can be used to estimate vegetation height in the Atlantic Forest as well. We conclude that vegetation height estimates with linear models can be used as a simple low cost alternative for future applications in this environment.     

Changes in seed rain across Atlantic Forest fragments in Northeast Brazil

The objectives of this study were to characterize the distribution of seeds in remnant fragments of the Atlantic Coastal Forest and to determine whether the species diversity, seed weight, and species composition of plant communities are altered by forest fragmentation. A transect of 100 m was established in the core of each of nine fragments of Atlantic Coastal Forest in a private sugarcane plantation in the state of Alagoas, NE Brazil, and ten seed-traps were distributed at intervals of 10 m each along the transects. For 12 consecutive months seeds were collected, dried, counted, weighed, and identified to species. Seeds were assigned to categories according to their size, dispersal mode, and shade tolerance. Multiple regression models and Mantel correlation tests were used to detect the effects of fragment size, percent forest cover nearby, distance from the source area, and distance from the nearest fragment on species diversity, mean seed weight, and species similarity. Analyses were carried out for all species and for subsets corresponding to each seed category. A total of 21,985 diaspores of 190 species were collected. Most seeds were small, shade-intolerant, and zoochoric, which corroborates other studies of fragmented forest landscapes and reflects the high disturbance levels in isolated forest remnants. Our data indicate that fragmentation processes such as habitat loss can alter species diversity and species composition by reducing habitat availability and increasing fragment isolation. We also found that large-seeded species are more affected by fragment isolation, possibly because their seed dispersers rarely cross non-forested areas between fragments, while zoochoric species are more strongly affected by fragment size and apparently more strongly associated with local edaphic conditions than with distance from seed sources.     

Response of the ground layer community of a cerrado vegetation in central Brazil to liming and irrigation

A split plot design with irrigation as the main plot treatment and liming as subplot treatment was utilized to determine the response of the ground layer community of a cerrado vegetation on a dystrophic dark red latosol (Haplustox) in central Brazil to liming and irrigation. Aerial live biomass of the grasses and nongrasses of the ground layer and their nutrient concentrations were determined over a period of 18 months. As liming rate increased from 0 to 8.4 t ha^-1 the soil pH increased from 5.2 to 5.8. The availability of Ca increased from 0.24 to 6.91 cmol (+) kg^-1 dry soil and that of Mg from 0.10 to 0.17 cmol(+)kg^-1 dry soil. Liming decreased the exchangeable Al from 0.66 to 0.24 cmol (+) kg^-1 dry soil. There was an increase of up to 70% in the biomass concentration of Ca in grasses and 87% in nongrasses as a result of liming up to 8.4 t ha^-1. Concentrations of Mn decreased by 37% in grasses and by 33% in nongrasses. However, liming did not result in any increase in the primary production of either grasses or nongrasses. Irrigation during the dry season did not alter soil pH, nutrient availability in the soil or foliar concentrations of nutrients in grasses and nongrasses. Irrigation during the dry season increased the live aerial biomass of grasses by an average of 41% over the experimental period but not that of the nongrasses.     

Food habits of sympatric opossums coexisting in small Atlantic Forest fragments in Brazil

The diets of sympatric species of opossums coexisting in small (<10 ha) Atlantic Forest fragments were studied at Poço das Antas Biological Reserve, southeastern Brazil. Food items consumed by Caluromys philander and Didelphis aurita were investigated through the analysis of faecal contents, and compared with the diet of Micoureus demerarae analysed in a previous study. The major diet components for all three species were arthropods and fruits, with a high richness of items of both feeding categories; feathers were also found in the diet of D. aurita. The most frequent insect orders overall were Hymenoptera and Coleoptera, and most seeds were from plants of secondary vegetation such as Cecropia and Piper. The diets showed little variation along time and space for all three species. Diets were also similar among species, except for a larger consumption of Arachnida and Diplopoda and a smaller consumption of Lepidoptera by D. aurita when compared to M. demerarae. Diversity of food items was lower for C. philander when compared with either other species. There was a high feeding niche overlap between species, suggesting that differentiation in diet composition would not be enough to allow coexistence of the three species in small fragments. Coexistence may rather be allowed by vertical segregation and/or by differences in prey size.     

Melissopalynology in an area of Atlantic Forest (northeast region,Brazil)

Apis mellifera is a bee that was introduced to Brazil and has adapted very well to the climate conditions and vast diversity of plants that exist in the country. In the northeast region of Brazil, beekeepers make use of the association between bees and plants by selling various bee products, notably honey. One way to identify species visited by bees in an area is by the pollen in its products. Based on this, 16 samples of honey were analysed, which were collected over a period of two years and obtained from an apiary in the Atlantic Forest biome in the municipality of Entre Rios (Bahia). In addition, climatic data (precipitation and temperature) of the region were obtained for the months sampled. The average temperature of the region during the collection months varied from 22 to 28 °C. The highest precipitation recorded in the region was 133.7 mm³ and the lowest was 0.3 mm³. Seventy pollen types were found. The family Fabaceae was notable, with ten pollen types, of which Mimosa pudica was the most important with a high frequency of occurrence and distribution. The Eucalyptus (Myrtaceae) pollen type also had a high frequency of occurrence and distribution. In addition, pollen types corresponding to species that supply nectar to bees were identified, which contributes to the large diversity of bee plants for Apis mellifera in the study area.     

Hunting Spiders of Woodland Fragments and Agricultural Habitats in the Atlantic Rain Forest Region of Brazil

The hunting spider communities of the Dionycha clade were studied 1986 through 1988 in fragmented woodlands and secondary agricultural habitats of the Botucatu area in São Paulo state, Brazil. The original vegetation of mainly tropical Atlantic rain forest (Mata Atlântica) was cleared already 70 years ago. In a total sample of over 1000 adult spiders, 247 species belonging to 12 families were determined. A decreasing frequency and diversity of spiders was found if forest remnants were compared with sugar cane fields and cattle pasture. The specific composition of the spider fauna as surveyed in different habitats is discussed under ecological aspects and in relation to the history of land use.     

Favolaschia in remnants of the Atlantic Forest,Brazil

The examination of recent collections of Favolaschia from remnants of the Atlantic Forest, Brazil, resulted in the identification of F. aurantiaca, F. cinnabarina and F. luteoaurantiaca sp. nov. Internal transcribed spacer (ITS) sequences obtained from these collections were introduced into the previously published phylogenetic tree of the genus to assess the position of these species within the Favolaschia clade. A maximum likelihood analysis generated a phylogenetic tree with a better resolution, especially for the clade that contains species belonging to section Favolaschia subsection Auriscalpium, where the three specimens collected in Brazil also were clustered in.     

Periodicity of growth rings in some flood-prone trees of the Atlantic Rain Forest in Rio de Janeiro, Brazil

The periodicity of growth ring formation was studied in Tabebuia cassinoides (Lam.) DC, Tabebuia umbellata (Sond.) Sandwith, Symphonia globulifera L., and Alchornea sidifolia Müll. Arg. in a swamp forest within the Atlantic Rain Forest of the state of Rio de Janeiro, southeastern Brazil. Mechanical wounds of the vascular cambium allowed cyclic growth to be observed, and the position of latewood relative to the wounds was analysed. Radial growth was correlated with phenology, temperature, precipitation, photoperiod, flooding regime, and endogenous rhythms. All species showed annual growth rings; however, there were different patterns of radial growth. Phenology was an important factor influencing the activity of the vascular cambium. The period of leaf abscission was correlated with the formation of latewood in three of the species studied, but it occurred at different times for each species. Flooding was a determinant of periodic growth in T. cassinoides; photoperiod was indirectly responsible for radial growth rhythm in T. umbellata, and endogenous rhythms accounted for the radial growth rhythm of S. globulifera and A. sidifolia.     

Physiognomic-structural characterization of dry- and humid-forest fragments (Atlantic Coastal Forest) in Pernambuco State,NE Brazil

Although both dry- and humid-forests have been intensively studied, their physiognomic and structural differences have not yet been well characterized. The present work seeks to identify the physiognomic and structural differences between fragments of humid- and dry-forests in the state of Pernambuco, Brazil. The humid-forest fragment was located in the municipality of São Vicente Férrer (7°37′ S × 35°28′ W) and the dry-forest fragment in the municipality of Aliança (7°38′ S × 35°14′ W). Fifty 10 × 20 m plots were delimited in each area and all individual living plants with a diameter at breast height (DBH) ≥5 cm were included. It was observed that the total density (1,390 ind ha^?1) and total basal area (29.9 m² ha^?1) were greater in the humid-forest than the dry-forest (649 ind ha^?1 and 18.7 m² ha^?1, respectively). Individual plants in the humid-forest tended to be taller, while those in the dry-forest had generally larger diameters. There were also differences in the most structurally important families as, for example, Clusiaceae, Moraceae, Myristicaceae, and Sapotaceae in the humid-forest and Sterculiaceae, Fabaceae, Bignoniaceae, and Moraceae in the dry-forest. Physiognomic differences were also observed in the different forest layers, as the group of species composing the canopy of the dry-forest are dominated by deciduous species, while many of the species in the understory are evergreen. In the humid-forest, both the understory and canopy are predominantly composed of evergreen species. The examination of the phytosociological parameters of average height and species richness allowed us to identify physiognomic differences between humid and dry forests in Pernambuco State. The present study demonstrated that dry forests are not simply floristic/structural subsets of humid forests, and that there is a great need to establish conservation areas to protect these important but spatially restricted forests within the Atlantic coastal domain.     

Ants Response to Human-Induced Disturbance in a Rain Tropical Forest

A high rate of human-induced disturbance of tropical ecosystems results in enormous loss of biodiversity due to local extinctions. Yet, mechanisms at the population level that lead to the extinction are still poorly understood. Here we tested the hypothesis that human-induced disturbance results in smaller amount of nesting sites for wood-dwelling arthropods that leads to smaller population size and diminished reproduction, and therefore, may promote local extinctions. We completed censuses in less-disturbed and human-disturbed secondary rain forest plots in Puerto Rico. We measured population size and brood production in wood-nesting ants and examined whether these parameters differ between less-disturbed and more-disturbed habitats. In addition, we measured volume of wood parts of all inhabited and potential nesting sites to assess nest site availability. We found that more human-disturbed forests furnish smaller nest sites, resulting in diminished population size and lowered brood production. Our study shows that human-induced disturbance decreases volume of available nesting sites that leads to decreased population size and lowered reproduction. Thus, in addition to the well-documented loss of species richness in human-disturbed tropical habitats, we demonstrated the direct effect of the disturbance that may promote vulnerability of local populations.     

Long-term stability of the hawkmoth fauna (Lepidoptera,Sphingidae) in a protected area of Brazilian Atlantic Rain Forest

Hawkmoths are an important component of tropical ecosystems, with significant roles as herbivores and pollinators. These moths can be used as indicators in biodiversity assessments because they can be easily sampled and identified. However, hawkmoths have seldom been surveyed over the long term for this purpose, especially in the Neotropical region. Considering that long-term datasets are of indisputable importance for understanding and monitoring temporal changes in biodiversity, this study assessed long-term changes in the hawkmoth fauna in a protected Atlantic Rain Forest area over a period of 64 years. We used historical and recent empirical datasets to ask whether faunal-diversity patterns and species composition have changed over time. We used individual- and sample-based rarefaction and extrapolation curves based on Hill number (diversity order of q = 0) to compare species richness, and the probability version of the abundance-based Chao-Jaccard index to assess beta diversity over time. To assess changes in faunal composition, we conducted a nonmetric multidimensional scaling analysis and performed an analysis of similarities to test whether the community composition has changed. Our results clearly showed long-term stability of the hawkmoth community over the 64 years, despite the growing human-induced landscape changes that occurred in the region surrounding the study area during the last 6 decades. This study emphasizes the importance of large remnants of Atlantic Forest for long-term maintenance of both functional diversity and ecosystem functioning.