Southwest Amazon Research Articles

Threats to the integrity of urban streams in the southwest amazon

This study characterized the physical integrity, hydromorphology, and limnology of ten urban streams in the Southwestern Amazon. The objective was to investigate how these characteristics covary and identify threats to the health of these ecosystems. The physical integrity of the streams was assessed using a Habitat Integrity Index (HII), hydromorphology based on width, depth, flow, and substrate type, and limnological characterization through 14 physico-chemical parameters during dry and rainy seasons. Three streams were classified as preserved, two as intermediate, and five as degraded. Anthropogenic alterations were observed in hydromorphological characteristics, especially in width, depth, and substrate type across different integrity categories. Limnological analysis revealed that chemical and biochemical oxygen demands, ammoniacal nitrogen, nitrate, dissolved iron, and sulfides exceeded the limits established by Brazilian water quality regulations (CONAMA 357/2005). The alteration of these parameters reveals that the primary threat to the integrity of these ecosystems is sewage collection and treatment issues, reflecting the absence of basic sanitation. Redundancy Analysis (RDA) indicated the influence of specific substrate types on parameters in degraded streams, while preserved streams showed a correlation between dissolved oxygen with riparian forest conditions and the absence of anthropogenic influence. Cluster analysis emphasized the importance of integrating environmental, hydromorphological, and limnological metrics for a comprehensive assessment of ecosystem health. Given the heterogeneity of Amazonian aquatic ecosystems, this study may contribute to the establishment of criteria based on regional characteristics for accurate assessment and guidance of public policies aimed at protecting and ensuring the integrity of these ecosystems. Keywords: limnological characteristics, microbiological analysis, Porto Velho, urbanization.

Biodiversity of carbapenem-resistant bacteria in clinical samples from the Southwest Amazon region (Rondônia/Brazil)

Brazil is recognized for its biodiversity and the genetic variability of its organisms. This genetic variability becomes even more valuable when it is properly documented and accessible. Understanding bacterial diversity through molecular characterization is necessary as it can improve patient treatment, reduce the length of hospital stays and the selection of resistant bacteria, and generate data for health and epidemiological surveillance. In this sense, in this study, we aimed to understand the biodiversity and molecular epidemiology of carbapenem-resistant bacteria in clinical samples recovered in the state of Rondônia, located in the Southwest Amazon region. Retrospective data from the Central Public Health Laboratories (LACEN/RO) between 2018 and 2021 were analysed using the Laboratory Environment Manager Platform (GAL). Seventy-two species with carbapenem resistance profiles were identified, of which 25 species carried at least one gene encoding carbapenemases of classes A (blaKPC-like), B (blaNDM-like, blaSPM-like or blaVIM-like) and D (blaOXA-23-like, blaOXA-24-like, blaOXA-48-like, blaOXA-58-like or blaOXA-143-like), among which we will highlight Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Serratia marcescens, and Providencia spp. With these results, we hope to contribute to the field by providing epidemiological molecular data for state surveillance on bacterial resistance and assisting in public policy decision-making.

Influence of the addition of carbon nanotube on the physical behavior of a lateritic soil from the southwest Amazon

In this work we evaluate the physical-mechanical behavior of lateritic soil with addition of carbon nanotubes. The soil was collected in a commercial deposit located in Rio Branco – AC and later characterized through particle size tests, X-Ray Diffraction, X-Ray Dispersion Spectroscopy and Tropical Compressed Miniature essay. The dispersion of nanotubes in solution was carried out and the size of the nanoparticles was verified using Dynamic Light Spreading - DLS, Zeta Potential and PDI. Three percentages of additions (0.05%, 0.1% and 0.2%) of carbon nanotubes were evaluated and compared with the control group according to the parameters of Atterberg limits, real density, dry density maximum and optimum humidity. The results indicate that the soil has a clayey behavior with a medium texture, with the presence of clay mineral kaolinite in its composition and silicon and iron oxides. The dispersion of carbon nanotubes reached particles with an average hydrodynamic diameter of 68.9 nm and Zeta Potential of -24.87 mV and PDI of 0.231, characterizing a solution as moderately dispersed and kinetically stable. The results of the liquidity limit and plasticity tests showed a reduction of 10 and 13%, respectively, with the addition of carbon nanotubes, while for the parameters of plasticity index, real specific mass, maximum dry density and optimal moisture, they did not show significant variation. Carbon nanotubes interact with soils with lateritic behavior, and further studies are essential to better understand the mechanisms behind this interaction.

Integrative taxonomy of Cercomacroides serva (Sclater, 1858) demonstrates the validity of C. hypomelaena (Sclater, 1890) comb. nov. (Aves: Thamnophilidae)

Abstract Cercomacroides serva is widely distributed in northern South America. However, this species has never been thoroughly evaluated taxonomically. We conducted a taxonomic study of three taxa currently classified under Cercomacroides serva, based on a study of 307 skins and 145 recordings of male loudsongs. Females from the northwest Amazonian population differ qualitatively from populations from the southwest Amazon in the coloration of the upperparts, primary, and tail. Male loudsongs are superficially similar between these two populations, but the shape of the notes differs significantly. There is no evidence of intergradation or clinal variation in female plumage or male loudsongs. Based on differences in plumage coloration, loudsongs, and lack of evidence of intergradation, we suggest that two species are best recognized. The name Cercomacroides serva is here restricted to populations north of the Marañon River in Peru, to the north in Ecuador, and in southwestern Colombia. The name Cercomacroides hypomelaenacomb. nov. is revived. This species is found south of the Marañon River, and on both banks of the Ucayali River in Peru, to the eastern left bank of the Madeira River in Brazil, and in northern Bolivia.

SUSTAINABLE MODULAR PROTOTYPE WITH BAMBOO FOR COMMUNITY CENTERS

This contribution presents the results of research carried out in two areas of the Peruvian Amazon within the framework of two community projects for technology transfer and capacity development in construction with bamboo, with the objective of designing and building a modular prototype with bamboo for 1/1 scale with the function of a community center, capable of incorporating sustainable strategies, replicability and adaptability, as an architectural alternative to the deterioration of the Amazonian natural and cultural habitat. The methodology contemplates two phases of experimentation, the first of design and construction of the Model Prototype in the Southwest Amazon (Pilcopata), studying the local context, the bamboo species, the participatory construction process, to formulate the modular proposal with the function of a Center Tourist Community; the second validation of the Prototype, identifying the bamboo species and adding a module in the design format for use in the Communal Transformation Center in the Central Amazon (Native Community of Pampa Michi), both executed with the local population. Among the results, the efficiency, practicality and flexibility of the design and construction stand out, and the verification of sustainable strategies, with the use of carbon neutral materials such as bamboo, the revaluation of traditional knowledge with palm leaves and the replicability in similar conditions with models of participatory learning, which validate the Prototype. In a third phase, the construction processes are systematized, being part of the Manual for the construction of light structures with bamboo in Peru.

Dynamics of Variation in Agricultural and Forest Areas in the Southwest Amazon (Sena Madureira, AC)

Objective: To analyze the dynamics of variation in agricultural areas in the southwest of the Brazilian Amazon, specifically in the municipality of Sena Madureira, Acre. Theoretical framework: The expansion of agriculture in the Brazilian Amazon is the result of new logistics associated with new flow modes that allow the insertion of their activities in areas with potential for use and occupation. Method: Use of geotechnologies to analyze the dynamics of variation in areas and forms of use and occupation of agriculture, based on data generated by MapBiomas, with the aid of the ArcGis 10.8 software. Use of linear regression, including coefficient of determination and bivariate analysis. Results and conclusion: Exponential growth of cattle ranching with grassland areas reaching 222,413 hectares in 2022, expanding preferentially both in the vicinity of the margins of the BR 364 and AC 339 highways and in the urban perimeter of Sena Madureira, while agriculture presented oscillatory amounts in hectares of area, suggesting its use for subsistence. The very strong relationship between forest and grassland variables with linear regression analysis, shows the growth of agricultural areas to the detriment of forest areas. The study made it possible to generate bases for understanding the lack of conciliation between economic growth and environmental preservation. Implications of the research: Generation of bases for understanding the relationship between agricultural economic growth and environmental preservation in the southwest of the Brazilian Amazon. Originality/value: The historical perspective concerning the comprehension of areas used for agricultural practices and the intersection with Amazonian environmental issues.

Remote sensing evidence for population growth of isolated indigenous societies in Amazonia

Isolated indigenous societies who actively avoid sustained peaceful contact with the outside world are critically endangered. Last year, “Tanaru”, the lone surviving man of his tribe for at least 35 years, died in Southwest Amazonia, marking the latest cultural extinction event in a long history of massacres, enslavement, and epidemics. Yet in the upper reaches of the Amazon Basin, dozens of resilient isolated tribes still manage to survive. Remote sensing is a reliable method of monitoring the population dynamics of uncontacted populations by quantifying the area cleared for gardens and villages, along with the fire detections associated with the burning of those clearings. Remote sensing also provides a method to document the number of residential structures and village fissioning. Only with these longitudinal assessments can we better evaluate the current no-contact policies by the United Nations and governments, along with the prospects for the long-term survival of isolated tribes. While the world’s largest isolated indigenous metapopulation, Pano speakers in Acre, Brazil, appears to be thriving, other smaller isolated populations disconnected from metapopulations continue to be extremely vulnerable to external threats. Our applied anthropological conservation approach is to provide analyses of publicly available remote sensing datasets to help inform policies that enhance the survival and well-being of isolated cultural groups.

Spatial–temporal analysis of the effects of hydropower plants over the artisanal fishing in the middle Madeira region, Southwest Amazon

Spatial–temporal analysis of the effects of hydropower plants over the artisanal fishing in the middle Madeira region, Southwest Amazon

Genetic Evidence for a Potentially New Pathogenic Leptospira sp. Circulating in Bats from Brazilian Amazon

Leptospirosis is a neglected zoonosis frequently reported worldwide, caused by a spirochete of the genus Leptospira. It is capable of infecting domestic animals, free-living animals, and humans. Among wild animals, the role of bats in the epidemiology of leptospirosis has been investigated but is far from being elucidated. The Amazonian biome has the ideal conditions for maintaining and disseminating leptospires and, despite efforts that have been made to better understand leptospires’ occurrence in wild animals in the region, few studies aimed to explore and genetically characterize leptospires in bats. Based on this, the aim of the present study is to deeper investigate and genetically characterize leptospires detected in bats from the southwest Amazon. Animals were trapped by mist netting at five sites in the state of Acre, Brazil. Kidney samples were obtained and stored for molecular analysis. Polymerase chain reaction (PCR) was conducted first based on the LipL32 gene, and positive samples were submitted to rrs and secY-PCR and sequencing. Sequences were then submitted to phylogenetic analyses through multiple bioinformatic tools. The rrs sequences from the present study formed one single haplotype, different from any other previously deposited, grouped in a highly supported cluster with sequences from bats from Madagascar and China. The initial secY screening revealed no identity with previously deposited sequences. The phylogenetic trees revealed the sequences from the present study in an isolated branch, clearly separated from all previously known pathogenic Leptospira spp., suggesting the existence of a potentially undescribed species. The haplotype network including only leptospires from the Amazon region confirmed two new haplotypes from the same taxon unity, isolated from the others, with a probable origin of the species from L. noguchii. The characterization of this potentially new species in bats reinforces the complexity of the transmission dynamics of leptospires, including wild, periurban, and urban environments, emphasizing the need for an integrative look at leptospirosis vigilance within the context of One Health.

Climate change over South America simulated by the Brazilian Earth system model under RCP4.5 and RCP8.5 scenarios

Climate projections simulated by the Brazilian Earth System Model (BESM2.5) under RCP4.5 and RCP8.5 climate scenarios are analyzed based on future changes of surface air temperature (SAT) and precipitation with respect to the historical reference period 1971–2000. Since BESM2.5 is the only climate model developed in a South American country, this study gives a particular emphasis to South American future climate projections. Regarding the surface air temperature, BESM2.5 projects a steady warming throughout the 21st century, with the highest warming over eastern Amazonia, northern Chile and central South America for both scenarios. The SAT changes range between 2 °C and 3–4 °C for RCP4.5 and RCP8.5, respectively. On the other hand, projected precipitation varies over different regions of South America, with decreasing and increasing trends over the Amazon and southern South America, respectively. Interestingly, this study shows contrasting results with respect to extreme precipitation indicators, projecting enhanced extreme events with higher numbers of both consecutive dry days and days in which the precipitation exceeds 20 mm over the southeastern region. The model projects a meridional dipole pattern in the precipitation, with decreasing precipitation and longer dry spells over Northeast Brazil and the East Amazon region and increasing precipitation and shorter dry spells over Northwest South America and West Amazon, that is driven by future changes in the SLP that imposes a meridional gradient over these regions, causing the increase of westerlies that are likely to increase the moisture transport from the Pacific Ocean into western South America and the weakening of the easterlies that transport moisture over eastern South America and East Amazon.

A New Species of Vampirolepis (Cestoda: Cyclophyllidea: Hymenolepididae) from the Bat Artibeus lituratus (Chiroptera: Phyllostomidae) in the Amazon Rainforest, Brazil

The Amazon biome has a great diversity of bat species. In the state of Acre, Brazil, there is an estimated occurrence of 64 bat species with the species of the genus Artibeus as one of the most abundant. Despite their abundance and widespread distribution within the biome, the helminth fauna from Amazonian bats is still poorly known. In this way, the objective of this study is to describe a new species of cestode from the genus Vampirolepis found in A. lituratus, collected at the Parque Estadual do Chandless, a natural preserved area, located in the Purus River Basin, Southwest Amazon, the state of Acre. The new species of Vampirolepis is distinguished from the others by the number and size of hooks, testes disposition, size of the cirrus sac, ovaries and internal and external seminal vesicles. Additionally, molecular study showed that this forms a paraphyletic clade with Vampirolepis elongatus.

Two new species of the ant-like spider genus Fluda Peckham & Peckham, 1892 from Bolivia with first reports of potential ant models for the genus and a novel ant-resembling behavior (Araneae: Salticidae, Simonellini)

In this work, the results of a survey for species of Fluda Peckham & Peckham, 1892 in primary forest in five Bolivian forest ecoregions are reported. Fluda dauca sp. nov. is described from Southwest Amazon forest and F. thuruampara sp. nov. from Bolivian Yungas forest. Fluda perdita (Peckham & Peckham, 1892) is reported from Bolivia for the first time. Both new species exhibited polymorphic mimicry; dark females of both species resembled the turtle ant Cephalotes pusillus (Klug, 1824) and dark males of F. thuruampara sp. nov. the carpenter ant Camponotus sanctaefidei Dalla Torre, 1892. Orange males and females of F. dauca sp. nov. are likely mimics of Camponotus latangulus Roger, 1863. Males of Fluda may compensate lower mimetic accuracy by the broadened femora I, resembling an ant head in lateral view and ant mandibles when moving the face towards a potential threat. As in other Simonellini, the turnover of Fluda species between the South American superregions suggests that significant shifts in seasonality and related conditions are major factors triggering speciation in the tribe Simonellini.

Starch grain analysis of ceramic residue from forest islands associated with raised fields in west central Mojos, Bolivia

This study analyzed starch grain residues from 65 ceramic artifacts recovered from excavations of inhabited forest islands situated near raised fields in the Llanos de Mojos region of the southwestern Amazon Basin. The assemblage of starch grains from the forest island contexts represents a diverse array of plant resources including maize and manioc, but also other plants such as achira, arrowroot, and the first archaeological evidence for arracacha in the southwest Amazon. The artifacts sampled and plants identified in this study represent resource use by people living on forest islands who constructed and maintained adjacent raised fields for cultivation. The study highlights the importance of research into the diversity of local and regional foodways in the Llanos de Mojos.

Detrital zircon U-Pb provenance analysis of Precambrian and Paleozoic strata from southwestern Brazil: Assessment of potential Grenvillian sediment input and Amazonian-Laurentian tectonic interaction

Southwest Amazonia is proposed to have collided with southeast Laurentia during the Grenville orogeny. In Laurentia, the collision produced a continental-scale late Mesoproterozoic to early Neoproterozoic clastic wedge dominated by detrital zircon (DZ) sourced from Grenvillian magmatic rocks (major Geon 11 and 10, with minor Geon 13, 12, and 9 ages: the “Great Grenvillian Sedimentation Episode”). New DZ ages in clastic units from southwestern Brazil permit testing the hypothesis that Grenvillian sediment from southeast Laurentia spilled onto western Amazonia during Rodinian assembly. Late Mesoproterozoic arenites are dominated by Geons 18, 17, 15, 14, and 13 ages sourced from Amazonia basement provinces. Two samples exhibit major Geon 12 and 11 ages with minor Geon 18–13 ages. Geon 12 and 11 correspond to a conspicuous age gap in Amazonian magmatic events. Latest Neoproterozoic samples exhibit minor Geon 13 to 9 ages interpreted to be sourced from the Rondônia-San Ignacio or Sunsás provinces of western Amazonia. Late Neoproterozoic and Devonian age spectra exhibit multiple Amazonian age modes ∼2500 to 500 Ma but with no dominant modes. The age distributions for all samples indicate a lack of Laurentian Grenville sediment influx to southwest Amazonia during Rodinian assembly and breakup. The enigmatic Geon 12 ages are interpreted to correspond to a buried Andean source or the southwestern Grenville province in Laurentia. In contrast to exposed basement in southwestern Amazonia, Andean basement clastic sequences and Pleistocene to Recent Amazon River sediments exhibit Grenville dominance of DZ ages, strikingly similar to eastern Laurentia clastic systems. The Andean Grenville dominance may be accounted for by extensive Grenvillian crust beneath the Andean clastic wedge containing a major component of Geons 12, 11 and 10 magmatic rocks, and which was not being fully exhumed until the Neoproterozoic, similar to Laurentian Grenville.

Diametric distribution of forestry species in riparian forest in the southern part of the Amazon

The expansion and changes in land use and land cover in the Southwest Amazon are mainly related to the activities of logging without management rules, agriculture and cattle production, which resulted in the conversion of natural forests, especially along water courses. This study aimed to verify the diametric distribution of forestry species with higher importance value index in the riparian forest of the Acre River (Acre, Brazil). The forestry inventory was performed at eight municipalities crossed by the Acre River, using two stage sample units (conglomerates) and applying stratified random sampling techniques at the river bank. Twenty-seven primary plots were installed, within which another four secondary plots were implanted. It was fitted Weibull’s probability density functions with 2 and 3 parameters to species diametric distribution, provided by the maximum likelihood method. Graphic analysis verified that 86% of the species analyzed presented a distribution trend with positive asymmetry. The distribution of the Weibull function with two parameters presented better the best estimative of the frequency of species by diameter class of the natural forest evaluated. Considering the heterogeneity of the species, further studies to verify whether the distribution behavior follows the same trend is recommended.

On the sympatric occurrence of two subspecies of Blue-crowned Manakin, Lepidothrix coronata exquisita and L. c. caelestipileata, in south-west Amazonia

I present evidence of sympatric occurrence of two subspecies of Blue-crowned Manakin Lepidothrix coronata in south-west Amazonia. Specimens collected in eastern Acre in Brazil and northern Bolivia, as well as records from south-east Peru, indicate that L. c. exquisita and L c. caelestipileata both occur in the south-east of the Inambari centre of endemism, when compared to their respective holotypes. Thus, L. c. exquisita, which was considered endemic to central-north Peru, is also present in the lowlands of south-west Brazilian Amazonia and northern Bolivia, whilst caelestipileata, previously known from the Juruá–Madeira region in Brazil, is present further south, reaching south-east Peru and northern Bolivia.

Lidar reveals pre-Hispanic low-density urbanism in the Bolivian Amazon

Archaeological remains of agrarian-based, low-density urbananism1–3 have been reported to exist beneath the tropical forests of Southeast Asia, Sri Lanka and Central America4–6. However, beyond some large interconnected settlements in southern Amazonia7–9, there has been no such evidence for pre-Hispanic Amazonia. Here we present lidar data of sites belonging to the Casarabe culture (around ad 500 to ad 1400)10–13 in the Llanos de Mojos savannah–forest mosaic, southwest Amazonia, revealing the presence of two remarkably large sites (147 ha and 315 ha) in a dense four-tiered settlement system. The Casarabe culture area, as far as known today, spans approximately 4,500 km2, with one of the large settlement sites controlling an area of approximately 500 km2. The civic-ceremonial architecture of these large settlement sites includes stepped platforms, on top of which lie U-shaped structures, rectangular platform mounds and conical pyramids (which are up to 22 m tall). The large settlement sites are surrounded by ranked concentric polygonal banks and represent central nodes that are connected to lower-ranked sites by straight, raised causeways that stretch over several kilometres. Massive water-management infrastructure, composed of canals and reservoirs, complete the settlement system in an anthropogenically modified landscape. Our results indicate that the Casarabe-culture settlement pattern represents a type of tropical low-density urbanism that has not previously been described in Amazonia.

Black Manakin (Xenopipo atronitens) as a keystone species for seed dispersal in a white-sand vegetation enclave in Southwest Amazonia

Black Manakin (Xenopipo atronitens) as a keystone species for seed dispersal in a white-sand vegetation enclave in Southwest Amazonia

A new species of the seasonal killifish genus Moema (Cyprinodontiformes: Rivulidae) from the Piraí watershed in the Southwest Amazon basin

Abstract Moema, a genus of the Rivulidae family, currently comprises 20 valid species. Most of these species inhabit temporary pools in the Amazon basin and only one species is found in the upper Paraguay basin. A new member of this genus from the upper Río Madeira drainage is here described. Males of the new species differ from all congeners by the combination of a color pattern consisting of oblique, sometimes chevron-like, irregular rows of red and light blue double-dots on body; dark yellowish to golden pectoral fins with no visible markings; and a stripe pattern on the ventral section of caudal fin with a very narrow black marginal line, intermittent or even absent. The existence of infrageneric species groups within Moema, the geographic distribution and taxonomic aspects of the species present in the Ríos Mamoré and Iténez/Guaporé rivers drainages, and the observation of intraspecific aggression between males and amphibious lifestyle in the new species are discussed.

Browse from Three Tree Legumes Increases Forage Production for Cattle in a Silvopastoral System in the Southwest Amazon.

Assessing the palatability of forage from locally adapted trees could improve the sustainability of livestock production systems. However, grasses continue to dominate livestock feed across the Amazon. We established a silvopastoral cattle farming system in Peru, comparing three different forage tree species with grass monocultures using a randomised block design. Trees were arranged in alleys of 0.5 × 7.5 m, planted alongside grass, and were directly browsed by cattle. Browse removal was estimated by three methods: destructive sampling, canopy measurements and leaf counts. We found that all three tree species were palatable to cattle. Plots containing trees and grass produced more available forage (mean > 2.2 Mg ha-1) for cattle than the grass monocultures (mean = 1.5 Mg ha-1). Destructive sampling below 1.6 m demonstrated that cattle consumed 99% of the available Erythrina berteroana forage, 75% of the available Inga edulis forage and 80% of the available Leucaena leucocephala forage in 8 days. This research demonstrates methodologies to estimate the intake of locally adapted browse species by cattle and highlights the potential benefits of silvopastoral systems in the Amazon. Planting trees could also benefit animal health and provide ecosystem services such as soil regeneration, enhanced nutrient cycling and carbon capture.