Neotropical Savanna Research Articles

Medium and large mammal responses to fire in a neotropical savanna system in Guyana

Medium and large mammal responses to fire in a neotropical savanna system in Guyana

Small hydropower dam alters the functional structure of macroinvertebrate assemblages in a Neotropical savanna river

Small hydropower dam alters the functional structure of macroinvertebrate assemblages in a Neotropical savanna river

Bird Leg Skin Lesions and Urbanization in a Neotropical Savanna City.

Urban sprawl threatens biodiversity and is responsible for significant changes in the species that live in these environments. Given the high cost of comprehensive surveillance, monitoring disease indirectly, such as detecting skin lesions in birds, may help us better understand the prevalence of diseases affecting wild populations. We assessed the frequency of leg skin lesions, as a proxy of disease presence, in 1,565 individuals of 25 species, along the urban matrix of a large Neotropical city, Brasília, Federal District, Brazil. We tested the hypothesis that there is an increase in the frequency of skin lesions in birds due to urban intensification. We observed an increasing trend in some bird species between the frequency of occurrence of lesions and the intensity of urbanization. Species with a higher number of captures had an increase in the percentage of lesions, indicating that the occurrence of lesions may be linked to higher population density or that detection of the effect occurs only when sample sizes are high and controlled among urbanization categories. Our study highlights how the intensity of urbanization may increase the risk of disease transmission for these species. Unfortunately, studies on this topic are scarce in Neotropical regions, despite the region's high biodiversity and urban expansion.

Fire triggers reestablishment of invasive grasses in a neotropical savanna under restoration

Fire triggers reestablishment of invasive grasses in a neotropical savanna under restoration

Comparative Metabolite Profiling of Three Savannic Species of Banisteriopsis (Malpighiaceae) via UPLC-MS/MS and Chemometric Tools.

Banisteriopsis (Malpighiaceae) is an important genus of neotropical savannas with related biological and medicinal activities but under-explored metabolomic profiles. We present a chemometric analysis for discriminating secondary metabolites of three species of Banisteriopsis (B. laevifolia, B. malifolia, and B. stellaris) leaves. Initially, each species was separately extracted with ethanol:water (4 : 1, v/v) and analysed by Ultra Performance Liquid Chromatography coupled with Mass Spectrometry (UPLC-MS/MS). The chromatographic profiles were subjected to Global Natural Product Social (GNPS) and Partial Least Squares Discriminant Analysis (PLS-DA). Eighty-nine compounds (cosine≥0.90) were annotated, including flavonoids, phenolics, and acids. The chemometric analysis (VIP Score) showed each species' relative concentration of the more relevant compounds. In addition, four compounds that discriminate the metabolomic profiles of B. laevifolia, B. malifolia, and B. stellaris were identified by PLS-DA.

Taxonomic, functional, and phylogenetic diversity of anuran assemblages across habitats and seasons in a Neotropical savanna

AbstractDifferences between habitats and seasonal changes in climate are some of the main factors responsible for shaping diversity patterns and biological community structures. In this context, anurans are considered excellent models for ecological studies due to their high sensitivity to environmental changes. This study analyzed how differences between open and forested formations and seasonality influence the taxonomic, functional, and phylogenetic diversity of anuran assemblages in an area of Neotropical savanna. Parameters of taxonomic (species richness—SR), functional (functional diversity—SES.FD, functional dispersion—FDis, and functional redundancy—FR), and phylogenetic diversity (phylogenetic species variability—PSV and phylogenetic species richness—PSR) were used to quantify spatiotemporal changes in the anuran assemblages. Sampling was carried out over 15 months, using pitfall traps and active searches. In total, we recorded 598 individuals belonging to 21 species and seven families. Species composition, SR, and PSR differed between habitats and seasons, the latter two being higher in open formations during the rainy season. SES.FD differed seasonally and was higher in the dry season. FDis, FR, and PSV did not differ between treatments. Anurans from forested formations were functionally and phylogenetically clustered during the rainy season, while those from open formations were functionally clustered during the same season. Habitat type and seasonal variation were important in determining the taxonomic, functional, and phylogenetic diversity of the anuran assemblages. However, changes in climate and land use are expected to negatively impact the ecological and evolutionary diversity of these organisms in the Cerrado, reinforcing the importance of conservation policies and actions.Abstract in Portuguese is available with online material.

Molecular Phylogeny and Historical Biogeography of Byrsonima (Malpighiaceae) Corroborates the Mid-Miocene Origins of Neotropical Savannas

We present a dated and calibrated molecular phylogeny for one of the most characteristic genera of Neotropical savannas, Byrsonima (Malpighiaceae), based on the ETS, ITS, and psbA-trnH markers. We sampled 33 species of Byrsonima and four species of the outgroups Blepharandra, Diacidia, and Pterandra to test the monophyly of the infrageneric classification of the genus. Bayesian inference (BI) analysis was performed for the combined molecular dataset. Seven morphological characters were optimized on the obtained tree. Calibration points derived from a published chronogram for Malpighiaceae were used alongside a relaxed, uncorrelated molecular clock on Beast 1.8.4. Ancestral range reconstructions focusing on four main Neotropical biomes (Cerrado, Atlantic rainforest, Amazon rainforest, and Caatinga dry forests) were performed on BioGeoBEARS. Our phylogenetic results corroborated the monophyly of Byrsonima, but all of its subgenera and sections were polyphyletic, with all morphological characters circumscribing these infrageneric ranks being highly homoplastic. The most recent common ancestor of Byrsonima was widespread in South American biomes at 11.41 Ma, posteriorly diversifying in the Amazon rainforests up to 7.72 Ma, when it started massively diversifying in Neotropical savannas. A few re-colonization events from savannas to rain or dry forests occurred from 2.95–0.53 Ma. These results corroborate the mid-Miocene origins of Neotropical savannas, and future studies should aim to sample Mesoamerican species of Byrsonima.

Leaf tolerance to heat is independent of leaf phenology in neotropical savanna trees

Leaf tolerance to heat is independent of leaf phenology in neotropical savanna trees

Beyond fire: Flower production naturally occurs and is also influenced by leaf removal in a Neotropical savanna herb.

Several herbaceous species exhibit mass flowering after fires in Neotropical savannas. However, unequivocal evidence of fire dependency and the consequences for plant reproduction are lacking. In nutrient-poor fire-prone savannas, the damage caused by fire and by other means (e.g., leaf removal, but not necessarily having a negative impact) constrains the maintenance and expansion of plant population by affecting the ability of individuals to recover. Therefore, the compensatory responses of plants to both damages should be convergent in such environments. Using Bulbostylis paradoxa-reported to be fire-dependent to flower-as a model, we investigated the role of fire and leaf removal in anticipating the flowering and reproduction periods, and its possible consequences on seedling establishment. We monitored 70 burned individuals, 70 damaged/clipped, and 35 without damage to estimate time for flowering, seed quality and germination parameters. To expand our sampling coverage, we examined high-resolution images from herbarium collections in the SpeciesLink database. For each herbarium image, we recorded the presence or absence of a fire scar, the month of flowering, and the number of flowering stalks. Bulbostylis paradoxa was fire-stimulated but not dependent on fire to flower, with 65.7% of the individuals flowering in the burned area, 48.6% in the clipped, and 11.4% in the control. This was consistent with the analysis of the herbarium images in which 85.7% of the specimens with flowers had fire scars and 14.3% did not. Burned individuals synchronized flowering and produced more viable seeds. However, the seeds might face a period of unsuitable ecological conditions after early to mid-dry season fires. Flowering of unburned plants was synchronized with the onset of the rainy season. Flexibility in flowering and vegetative reproduction by fragmentation confer to this species, and most likely other plants from the herbaceous layer, the capability of site occupation and population persistence in burned and unburned savanna sites.

Macroecological patterns of functional and phylogenetic diversity vary between ground and arboreal assemblages in Neotropical savanna ants

Macroscale environmental gradients can have contrasting effects on organisms that occupy different vertical niches, but we have little understanding of how this might result in different macroscale diversity patterns in ground and arboreal communities. We also have little understanding of how different dimensions of diversity, such as functional and phylogenetic diversity, vary along macroscale environmental gradients. Here we examine latitudinal and elevational patterns of different dimensions of diversity for both ground and arboreal assemblages in Neotropical savanna ants. The study was based on ant species occurring at 32 sites covering a 22° range of latitude and > 1000 m range in elevation in Brazil. Functional and phylogenetic richness were positively correlated with species richness, all increasing with latitude. However, the greater phylogenetic richness on the ground than in trees did not simply reflect differences in species richness. The mean functional and phylogenetic divergence among species was also greater on the ground than in trees, indicating a stronger role of competition. Both mean functional and phylogenetic divergence showed negative correlations with elevation in trees but not on the ground. In trees, the standardized effect size (taking into account differences in species richness) of mean functional divergence was negatively related to elevation and mean phylogenetic divergence was negatively related to both latitude and elevation. These findings suggest that as temperature decreases the relative importance of environmental filtering in arboreal but not ground communities increases (and that of competition and niche partitioning decreases). Overall, we show that the macroecological patterns of ant species richness that have previously been reported for Brazilian savannas do not adequately represent other dimensions of diversity, and that the representativeness differs between vertical strata. Macroecological patterns of functional and phylogenetic divergence indicate that the relative importance of competition and environmental filtering also differs between vertical strata.

Ant-plant networks exhibit distinct species diversity but similar organization in urban and wild areas of neotropical savannas

Ant-plant networks exhibit distinct species diversity but similar organization in urban and wild areas of neotropical savannas

Coordination of bark and wood traits underlies forest‐to‐savanna evolutionary transitions

AbstractAimTo test the hypothesis that adaptive shifts leading to the assembly of tropical savannas involved coordination between bark and wood traits and to understand the underlying mechanisms.LocationTropical South America.TaxonAngiosperms (woody).MethodsWe compiled data on three bark traits (total, inner and outer relative bark thickness), wood density, maximum height, five secondary xylem traits and on species' habitat information (light environment, climate, soil and fire history) for Neotropical savanna, forest and generalist species (biome groups). We tested for pairwise and multivariate associations among traits across species and if biome group and habitat conditions explained species positions along the resulting strategy axes.ResultsTraits covaried along four different axes. The first axis was consistent with a trade‐off between fire (thick barks) and shade tolerance (low bark to diameter ratio, high vessel density) and contributed to differentiate the three biome groups according to the preference for shaded environments. Forest species also differed from savanna and generalist species in a separate axis by being more resource acquisitive. Maximum height and wood density did not strongly trade‐off with bark thickness, although maximum height was negatively covaried with relative outer bark thickness. Preference for shaded conditions was the main driver of variation in the two principal strategy axes, but temperature, fire and soil sand content also explained differences in plant stature between savanna and generalist species.Main ConclusionsAllocation to bark is constrained by trade‐offs with wood, opposing shade‐tolerant and acquisitive forest species to fire‐resistant and conservative savanna species. Rather than a single strategy axis, three axes are necessary to understand the functional differences among savanna, forest and generalist species. Because two of these axes are controlled by light availability, the associated traits tend to covary in space and time, but not across species.

Habitat Selection of Three Neotropical Grassland Birds Is Dependent on Vegetation Structure and Resources

Grassland birds are globally imperiled. Those of endemic Neotropical savannas may be particularly threatened as knowledge of the ecology of many species is lacking, restricting our ability to take decisive conservation action. During the dry (non-breeding) season of 2010, we studied the population size, distribution, and habitat associations of the Cock-tailed Tyrant (Alectrurus tricolor), Black-masked Finch (Coryphaspiza melanotis), and Wedge-tailed Grass-finch (Emberiziodes herbicola) across a disturbance-mediated savanna–grassland gradient in Beni, Bolivia. We used distance sampling and surveyed structural and resource-specific habitat features at plots where birds were present versus random locations. Occupancy models identified fine-scale habitat associations. Cock-tailed Tyrant (7.1 ind./km2) specialized on open habitats in areas expected to be heavily inundated in the wet season, avoided trees, and selected tall grassy swards. Black-masked Finch (25.1 ind./km2) occurred across the gradient, associating with tall, forb-rich swards, sparse shrubs, and low levels of fruiting and seeding vegetation. Wedge-tailed Grass-finch (27.9 ind./km2) also occurred across the gradient, particularly associated with tall, forb-rich swards, abundant seeding grasses, and sparse shrubs. Our results offer the first quantitative abundance estimates for these species in Beni, provide vital baselines for future monitoring, and improve knowledge of the ecology and conservation management needs of these species. Importantly, our results suggest that populations of these three grassland birds may be best maintained in heterogenous, mosaic landscapes that can be produced by carefully managed burning and grazing. Further research in the breeding season would facilitate making stronger, more specific management recommendations.

Mercury distribution, bioaccumulation, and biomagnification in riparian ecosystems from a neotropical savanna floodplain, Araguaia River, central Brazil

Litterfall is the main source of dry deposition of mercury (Hg) into the soil in forest ecosystems. The accumulation of Hg in soil and litter suggests the possibility of transfer to terrestrial invertebrates through environmental exposure or ingestion of plant tissues. We quantified total mercury (THg) concentrations in two soil layers (organic: 0–0.2 m; mineral: 0.8–1 m), litter, fresh leaves, and terrestrial invertebrates of the Araguaia River floodplain, aiming to evaluate the THg distribution among terrestrial compartments, bioaccumulation in invertebrates, and the factors influencing THg concentrations in soil and invertebrates. The mean THg concentrations were significantly different between the compartments evaluated, being higher in organic soil compared to mineral soil, and higher in litter compared to mineral soil and fresh leaves. Soil organic matter content was positively related to THg concentration in this compartment. The order Araneae showed significantly higher Hg concentrations among the most abundant invertebrate taxa. The higher Hg concentrations in Araneae were positively influenced by the concentrations determined in litter and individuals of the order Hymenoptera, confirming the process of biomagnification in the terrestrial trophic chain. In contrast, the THg concentrations in Coleoptera, Orthoptera and Hymenoptera were not significantly related to the concentrations determined in the soil, litter and fresh leaves. Our results showed the importance of organic matter for the immobilization of THg in the soil and indicated the process of biomagnification in the terrestrial food web, providing insights for future studies on the environmental distribution of Hg in floodplains.

Increasing fire severity alters the species composition and decreases richness of seeds potentially dispersed by small mammals

AbstractSeed dispersal is a key process that influences the recruitment of plant species, yielding profound consequences on vegetation structure. This process can be affected by environmental disturbances, such as fires, leading to varied impacts on the agents involved, both dispersers and plants. We investigated the potential role of small mammals (rodents and marsupials) as seed dispersers in a Neotropical savanna (Brazilian Cerrado). We also evaluated the impact of fire severity on the seed dispersal services provided by these animals in gallery forests, 3 years after a major fire event. We live‐trapped small mammals in 14 sites, 7 of which were located in forests classified in three categories of fire severity (“unburned”, “low severity”, or “moderate severity”). We captured 13 mammal species, finding a total of 11,688 seeds in their feces (collected inside traps or handling bags). These seeds encompassed 28 plant species from at least 8 families. A multivariate analysis (NMDS) revealed differences among small mammal species in terms of potentially dispersed plants, with seeds of 18 plant species being consumed by no more than one small mammal species. An increase in fire severity affected the composition of plant species potentially dispersed, changed the relative role of forest small mammals as seed dispersers, and decreased observed richness of defecated seeds. We conclude that high‐severity wildfires affect highly relevant ecological processes, such as seed dispersal by animals. These effects could impact the recruitment dynamics of plant species and, consequently, the vegetation recovery and plant community composition in fire‐affected areas.Abstract in Portuguese is available with online material.

A new species of Dolichurus Latreille (Hymenoptera, Apoidea, Ampulicidae) from Brazil

A new species of Dolichurus Latreille (Hymenoptera, Apoidea, Ampulicidae) from Brazil Dolichurus sensei Ferreira and Lopez sp. nov. is described based on a single female specimen from a Neotropical savanna fragment in São Carlos, São Paulo, Brazil. We include images of the holotype and provide an additional commentary on its coloration.

Influence of soil properties on woody vegetation structure, diversity and seasonality in Neotropical savannas

AbstractUnderstanding how savanna soil properties influence vegetation diversity and function is a major challenge in ecological studies. We investigated the effects of soil properties on woody species density, richness, composition, and vegetative phenology (inferred by the Normalized Difference Vegetation Index (NDVI)) in two alluvial and two interfluvial savanna sites (1 block of 10 plots of 20 × 50 m in each site), in the Brazilian Cerrado. We showed that plots in alluvial savannas present less fertile soils and have lower plant densities and species richness and higher seasonality of NDVI than plots in the interfluvial savannas. The species composition of the sites was associated with the P, Fe, K, and Mn content of the soil. Soil K, Fe, and Ca contents were the main variables associated with plant density in a linear mixed model (LMM) that explained 79% of data variability (r2c = 0.79%), and K, Fe, and Al were the main predictors to explain species richness (r2c = 0.81%). Soil K, pH, and Silt were the best predictors of the seasonality in NDVI (r2c = 0.14%). We highlight the all‐encompassing effect of K soil content on species density, richness, composition, and NDVI and argue that this macronutrient and a few other soil properties (e.g., P, Fe, Al, and Silt) are the main factors mediating plant responses to water and nutrient stress in woody savanna communities occurring in the Cerrado–Amazônia transition.

Termites are key drivers of short‐term deadwood decay in Neotropical Cerrado across vegetation types

AbstractThe impact of deadwood in ecosystems is dependent on its longevity, as determined by decay rates controlled by decay agents. Despite the importance of macroclimate, significant variation of decay rates within a given macroclimatic envelope has been reported. Such variation may be driven by local‐scale microenvironmental conditions as regulated by the plant community structure as well as the presence of specific biotic and abiotic decay agents, decoupling the relation between macroclimate conditions and deadwood decay rates. In this study, we evaluated the relation between local‐scale variation in plant community structure with the decay rates of deadwood and the relative importance of biotic and abiotic decay agents in deadwood decay in Neotropical Cerrado. For this, we performed a wood mass loss experiment using Pinus taeda wood which was installed at three sites in three vegetation types differing in canopy cover—grasslands, savannas and woodlands; wood was divided into treatments according to deadwood exposure to decay agents—microorganism, termite and solar radiation. Across sites, we found termites and microbes decomposed wood twice as fast as microbes alone, while solar radiation was not a strong driver of deadwood decay in our sites. Additionally, local‐scale variation in plant community structure affected deadwood decay, as decay rates and frequency of wood blocks discovered by termites were lower in woodlands than in grasslands and savannas. Our study highlights the interactive effects of local‐scale variation in plant community structure and termites on deadwood turnover, mainly due to differences in termite foraging behaviour among vegetation types and highlights the key role of termites in deadwood decay throughout Neotropical savannas.

Strategies of air space acquisition in Neotropical savanna trees differing in leaf habit

Strategies of air space acquisition in Neotropical savanna trees differing in leaf habit

From leaves to the whole tree: Mistletoe effects on the productivity, water relations, and demography of a Neotropical savanna tree

AbstractTrees' responses to mistletoes occur at multiple organization levels (e.g., leaf, individual, population), yet integrating these multi‐scale responses is still challenging. Here, we compared the traits of infected versus uninfected trees over multiple scales, from leaf anatomy and physiology to canopy allometries and individual growth rate and survivorship. We tested the hypotheses that mistletoes lead in the host (1) the production of leaves with a conservative resource‐use strategy, (2) more mechanically stable canopies and (3) reductions in growth and survival probability in the trees they infect. We addressed these hypotheses in the widespread savanna tree Vochysia thyrsoidea and xylem‐tapping mistletoe Psittacanthus robustus in the Brazilian Cerrado, a global biodiversity hotspot. We found that (1) mistletoe infection did not affect key traits associated with resource conservativeness, such as leaf mass per area (LMA) and carbon assimilation rates (A). Likewise, (2) hosts did not increase the mechanical safety of their trunks in response to mistletoe infection since infected and uninfected trees had a similar allometric scaling between height and crown volume against stem diameter. (3) At the population level, both the relative growth rate and survival probability decreased as the number of parasites increased. However, zero growth and a 50% chance of mortality were estimated to occur in a minority of heavily infected trees (>7 and 14 parasites, respectively). Our results challenge the idea that mistletoes have a ubiquitous negative impact on their hosts. We highlight, therefore, the need for clarifying the mechanisms that allow trees to maintain their functioning even in the face of mistletoe parasitism.