23736 research outputs found
Sort by
Planetary boundary layer evolution over the Amazon rainforest in episodes of deep moist convection at the Amazon Tall Tower Observatory
Full text linkIn this study, high-frequency, multilevel measurements, performed from late October to mid-November of 2015 at a 80m tall tower of the Amazon Tall Tower Observatory (ATTO) project in the central state of Amazonas, Brazil, were used to diagnose the evolution of thermodynamic and kinematic variables as well as scalar fluxes during the passage of outflows generated by deep moist convection (DMC). Outflow associated with DMC activity over or near the tall tower was identified through the analysis of storm echoes in base reflectivity data from an S-band weather radar at Manaus, combined with the detection of gust fronts and cold pools utilizing tower data. Four outflow events were selected, three of which took place during the early evening transition or nighttime hours and one during the early afternoon. Results show that the magnitude of the drop in virtual potential temperature and changes in wind velocity during outflow passages vary according to the type, organization, and life cycle of the convective storm. The nocturnal events had well-defined gust fronts with moderate decreases in virtual potential temperature and increases in wind speed. The early afternoon event lacked a sharp gust front and only a gradual drop in virtual potential temperature was observed, probably because of weak or undeveloped outflow. Sensible heat flux (H) increased at the time of the gust front arrival, which was possibly due to the sinking of colder air. This was followed by a prolonged period of negative H, associated with enhanced nocturnal negative H in the wake of the storms. In turn, increased latent heat flux (LE) was observed following the gust front, owing to drier air coming from the outflow; however, malfunctioning of the moisture sensors during rain precluded a better assessment of this variable. Substantial enhancements of turbulent kinetic energy (TKE) were observed during and after the gust front passage, with values comparable to those measured in grass fire experiments, evidencing the highly turbulent character of convective outflows. The early afternoon event displayed slight decreases in the aforementioned quantities in the passage of the outflow. Finally, a conceptual model of the time evolution of H in nocturnal convective outflows observed at the tower site is presented. © Author(s) 2020
Multilocus data of a manakin species reveal cryptic diversification moulded by vicariance
No full textWe used molecular tools and a multilocus approach to investigate the phylogeography of Lepidothrix coronata across most of its ample range. We sequenced six DNA fragments to produce phylogenies, molecular dating estimates, analyses of the dynamics of the demographic history of the species and a biogeographic analysis to estimate the events and changes in the ancestral distribution of the species. The results indicated the presence of four well-established lineages, with high levels of divergence. These lineages are delineated by well-defined geographic barriers, with one lineage, restricted to the west of the Andes, being the first to diverge from the complex. The other three lineages are exclusive to the Amazonian distribution of the species, with two being found north of the Amazon River, and the third, south of the Amazon. Some of the relationships found between these lineages were distinct from those described in previous studies. Important disagreements were found between the mtDNA phylogeny and that of the multilocus analysis, in relation to the lineages located to the west of the Andes. We propose that past introgression events may have influenced shifts in the relationships between lineages, despite the fact that the groups were well defined in both the phylogenies. The biogeographic analysis indicates that the lineages arose through successive vicariance events, which had a primary role in the diversification of the group. Two or three genetically structured subclades were also found within each Amazonian lineage, although these subclades are not isolated by an obvious geographic barrier. © 2019 Royal Swedish Academy of Science
Individual variation in feather corticosterone levels and its influence on haemosporidian infection in a Neotropical bird
No full textCorticosterone (CORT) is the main glucocorticoid hormone of amphibians, reptiles, birds and some mammals. This hormone may have evolved as an adaptive metabolic mechanism, in part because increased concentrations of CORT are essential for individuals to manage energy resources and thus cope with negative perturbations such as predation and storms. The benefits of CORT are offset by costs, because elevated levels can suppress inflammatory responses of individuals, making them more susceptible to parasites and pathogens. In this study, we investigated the relationships between feather CORT levels, infection status and diversity of haemosporidian parasites in the Blue-crowned Manakin Lepidothrix coronata, considering possible effects related to the sex and age of individuals. We predicted higher levels of feather CORT in infected individuals. We observed that feather CORT levels were similar among individuals of different sexes and ages. Although haemosporidian infection status did not vary among sexes, occurrence probability was higher among younger individuals, which may indicate that the less developed immune system of these individuals makes them more susceptible to avian malaria. Contrary to expectations, we found that feather CORT levels were not associated with the infection status and diversity of haemosporidian parasites. That haemosporidian occurrence probability does not increase with elevated feather CORT levels suggests that individuals are not immunosuppressed by elevated levels of this hormone, at least to the extent that feather CORT truly reflects individual differences in the level of this hormone. © 2019 British Ornithologists’ Unio
Physical, Chemical, Morphological and Mineralogical Characterization Surface and Subsurface in Hydromorphic and Non-hydromorphic Soil of the Central Amazon
No full textPhysicochemical features of Amazonian water typologies for water resources management
Full text linkToday, an increasing amount of hydrochemical data indicate that the chemical composition of Amazonian rivers varies much more than the traditional classification indicates. In this first comprehensive review of Amazonian river chemistry, we synthesized critical information from 400 scientific publications and distinguish the types: white, black, clear, intermediate type A and type B. We show the distribution of such rivers across the Amazon basin and the limitations of such approach. These insights into Amazonian river classification provide a new understanding of their baseline limnological conditions. They have implications for sustainable management of Amazonian freshwater systems. © 2020 IOP Publishing Ltd
On the scaling of activity in tropical forest mammals
No full textActivity range – the amount of time spent active per day – is a fundamental aspect contributing to the optimization process by which animals achieve energetic balance. Based on their size and the nature of their diet, theoretical expectations are that larger carnivores need more time active to fulfil their energetic needs than do smaller ones and also more time active than similar-sized non-carnivores. Despite the relationship between daily activity, individual range and energy acquisition, large-scale relationships between activity range and body mass among wild mammals have never been properly addressed. This study aimed to understand the scaling of activity range with body mass, while controlling for phylogeny and diet. We built simple empirical predictions for the scaling of activity range with body mass for mammals of different trophic guilds and used a phylogenetically controlled mixed model to test these predictions using activity records of 249 mammal populations (128 species) in 19 tropical forests (in 15 countries) obtained using camera traps. Our scaling model predicted a steeper scaling of activity range in carnivores (0.21) with higher levels of activity (higher intercept), and near-zero scaling in herbivores (0.04). Empirical data showed that activity ranges scaled positively with body mass for carnivores (0.061), which also had higher intercept value, but not for herbivores, omnivores and insectivores, in general, corresponding with the predictions. Despite the many factors that shape animal activity at local scales, we found a general pattern showing that large carnivores need more time active in a day to meet their energetic demands. © 2020 Nordic Society Oikos. Published by John Wiley & Sons Lt
Composition and Diversity of Fungal Decomposers of Submerged Wood in Two Lakes in the Brazilian Amazon State of Pará
Full text linkAquatic ecosystems in tropical forests have a high diversity of microorganisms, including fungi, which are important decomposers of submerged wood. Despite the importance of their role in decomposition, research concerning the diversity of freshwater fungi from Brazilian Amazonian environments is scarce. The aim of this work was to describe the composition and diversity of fungi present on submerged wood in two lakes of the Brazilian Amazon (State of Pará). Fragments of decaying wood (30 samples per lake) were collected from the Lakes Juá and Maicá. The wood samples were inspected for 6 months in the presence of fungal reproductive structures. Fungi observed in the wood were identified morphologically. Twenty-three taxa were identified in the Lake Juá (10 sexual and 13 asexual) and 26 taxa in the Lake Maicá (17 sexual, 9 asexual). ITS sequences were obtained for 14 taxa to aid in identification. In the Lakes Juá and Maicá, the diversity indices were H': 2.6514 and H': 2.8174, respectively. The Sørensen index of the fungal communities in the studied lakes was 0.3673. This study is the first to describe the fungal biodiversity of two important aquatic environments in Pará, Brazil. © 2020 Eveleise Samira Martins Canto et al
Swimming performance and use of energetic substrates in two species of pacu (Metynnis argenteus and Myloplus asterias) from Anavilhanas National Park, Amazonas
No full textHistorical demography and climate driven distributional changes in a widespread Neotropical freshwater species with high economic importance
Full text linkThe Neotropical region exhibits the greatest worldwide diversity and the diversification history of several clades is related to the puzzling geomorphologic and climatic history of this region. The freshwater Amazon ecoregion contains the main hydrographic basins of the Neotropical region that are highly dendritic and ecologically diverse. It contains a rich and endemic fish fauna, including one of its most iconic and economically important representatives, the bony-tongue Arapaima gigas (Teleostei, Osteoglossiformes). Here, we evaluated the projected distribution of the genus in different historical periods (Present, Last Glacial Maximum, Last Interglacial Maximum and Near Future) and interpreted these results in light of the genomic diversity and modeled historical demography. For that, we combined species distribution models, population genetic analysis using SNPs and deep learning model selection. We analyzed a representative sample of the genus from the two basins where it naturally occurs, four localities in the Amazon (Am) and three in the Tocantins-Araguaia (To-Ar) basin, as well as individuals from three fish farms. We inferred a potentially smaller distribution in the glacial period, with a possible refuge in central Am. Our genetic data agrees with this result, suggesting a higher level of genetic diversity in the Am basin, compared to that observed in To-Ar. Our deep learning model comparison indicated that the To-Ar basin was colonized by the population from the Am basin. Considering a global warming scenario in the near future, A. gigas could reach an even larger range, especially if anthropogenic related dispersal occurs, potentially invading new areas and impacting their communities. © 2020 The Authors. Ecography published by John Wiley & Sons Ltd on behalf of Nordic Society Oiko