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The diurnal cycle of precipitation in the Amazon Basin (AB) is not homogeneous, varying in its intensity, time of occurrence of precipitation peaks and in the shape of its diurnal distribution. This study presents a seasonal characterization of the mean diurnal cycle of precipitation in the AB from IMERG Final Run (Δx = 0.1° and Δt = 30 min) database from 2001 to 2020. Diurnal and semi-diurnal oscillations were studied by harmonics analysis, i.e., using the first and second harmonics, respectively. Harmonic metrics of normalized amplitude (AN), phase and mean hourly precipitation rate were analyzed. The AN showed pixels within the AB with bimodal/uniform or unimodal distribution associated with the occurrence of two peaks (or none) or a single peak during the day. The phase of the first harmonic shows the time of occurrence of the precipitation rates peaks, as well as the displacement of the precipitation systems. The regionalization of the diurnal cycle was performed using the K-Means technique, showing that AB presents six clusters along its domain based mainly on the phase of the first harmonic. The spatial configuration of clusters showed seasonal variation, being modulated by the South American Monsoon System and the large-scale mechanisms responsible for triggering convection. However, their intensity, the shape of the diurnal distribution and the timing of precipitation peaks are modulated by local factors. [ABSTRACT FROM AUTHOR]

In this study, a new species of Rhyacoglanis is described from the Jamanxim River basin, Tapajós River basin. The new species differs from congeners based on the combination of the following diagnostic characters: two oblique dark bands formed by an agglomerate of melanophores on the predorsal region; dorsal confluence between the dark subdorsal and subadipose bands in large juveniles and adults; ventral confluence between the dark subadipose and caudal peduncle bands; body without conspicuous dark brown spots; complete dark band on caudal peduncle; body with three dark bands; a thin dark caudal-fin band; pectoral-fin spine with anterior serrae distributed along the entire margin; the posterior tip of the post-cleithral process reaching vertical through the base of the dorsal-fin spine; and hypural 5 free of hypural 3 and 4 and pointed caudalfin lobes. Additionally, our molecular phylogenetic results using ultraconserved elements (UCEs) corroborate the new species as Rhyacoglanis and sister to an undescribed species of Rhyacoglanis from the Xingu River basin. Moreover, as pointed out in previous studies, we confirm Cruciglanis as a sister group to Pseudopimelodus plus Rhyacoglanis. [ABSTRACT FROM AUTHOR]

Phenacorhamdia nigrolineata is redescribed, and the expansion of its geographic distribution is presented based on abundant new records. Morphological analysis, meristic comparison and osteological description were performed. No one autapomorphy was identified for P. nigrolineata, but the species is identified by an exclusive combination of characters of coloration of the body, morphometric and meristic data (snout length, maxillary and outer mental barbels length; number of vertebrae). A discussion of its geographic distribution, coloration pattern of the body, the putative relationships among some species of the genus, and its conservation status are presented. [ABSTRACT FROM AUTHOR]

Rheumatic heart disease (RHD) continues to be a burden in low- and middle-income countries and prevalence estimates are lacking from South America. We aimed to determine the prevalence of RHD in the Brazilian Amazon Basin. We examined a random sample of adults (≥18 years) from the general population, who underwent echocardiographic image acquisition by a medical doctor. All images were analyzed according to (i) the 2012 World Heart Federation criteria and (ii) a simplified algorithm for RHD from a previously validated risk score (categories: low-, medium-, high-risk) which involved assessment of the mitral valve (leaflet thickening and excessive motion, regurgitation jet length) and aortic valve (thickening and any regurgitation). A total of 488 adults were screened (mean age 40 ± 15 years, 38% men). The prevalence of RHD was 39/1000 adults (n = 17 definite and n = 2 borderline). Fourteen (74%) had pathological mitral regurgitation, four (21%) mitral stenosis, 0 (0%) pathological aortic regurgitation and six (32%) both mitral and aortic valve disease. None had a prior diagnosis of RHD, 10 (53%) had positive cardiac auscultation and two (11%) reported a history of rheumatic fever. The simplified algorithm identified four (21%) adults as low-risk, six (32%) as intermediate, and nine (47%) as high-risk. The prevalence of RHD was 39/1000 in adults from the Brazilian Amazon Basin, indicating the need for screening programs in remote areas. A simplified model was only able to categorize every second case of RHD as high-risk. External validation of simplified screening models to increase feasibility in clinical practice are encouraged. • Rheumatic heart disease (RHD) is a burden in low- and middle-income countries. • This is the first study to investigate RHD in the Brazilian Amazon Basin. • By echocardiographic screening the incidence was 39/1000 adults. • Screening programs to diagnose RHD are encouraged in the Amazon Basin. [ABSTRACT FROM AUTHOR]

The increase in the greenhouse gas emissions leads to changes in the mechanisms connecting the two major river basins in South America, the Amazon and La Plata basins, at subcontinental scale. Studies very often neglect to address the impact of the model-component choices on the projected change in precipitation in the two river basins. Within that context, the present study investigates the probable causes of changes in the hydroclimate of the two river basins through projections from three global climate models—driven by the pathway with no stabilization of the emissions growth by 2100—with focus on the warming of regions in the equatorial Atlantic and Pacific Oceans. Because the annual cycle of the precipitation differs in the northern and southern portions of the two river basins, changes are then preferably assessed in subregions. The model-dependent results project the following changes in the physical and dynamic mechanisms toward the end of the twenty-first century: (i) intensification of the 850-hPa northerly moisture flux from the western tropical Atlantic in the eastern side of the central Andes; and (ii) increase in the magnitude of the 200-hPa wind core whose location largely coincides with the La Plata basin. Those changes may increase the precipitation in the northern Amazon and southern La Plata basins by the end of the century. In contrast, the decrease in precipitation in the northern La Plata basin may result from the decrease in length of the rainy season associated with South American Monsoon System. [ABSTRACT FROM AUTHOR]

For over a century, Lepidosiren paradoxa has been recognized as the single lungfish species in South America. Previous studies have failed to identify morphological differences in lungfish populations inhabiting the Amazon and Paraná–Paraguay River basins. Here, we report molecular evidence of cryptic speciation in South American lungfish. Our analysis of mitochondrial gene sequences from 56 L. paradoxa individuals collected in the Amazon and Paraná–Paraguay river systems revealed that genetic distances between individuals from different basins were on average 20 times greater than those obtained for individuals that occur in the same basin. Haplotype network did not uncover shared haplotypes between basins. Additionally, the species delimitation analysis showed that the posterior probability for the existence of distinct species is highly significant (PP = 0.99961). The phylogenetic analyses (BI and ML) recovered individuals from distinctive basins in reciprocally monophyletic clades. Our divergence time estimate suggests that the Lepidosiren in the Amazon basin are seven million years split from those that occur in the Paraná–Paraguay basin. On the other hand, in agreement with previous reports, our morphological comparison of 20 specimens from the Amazon and 14 specimens from the Paraná–Paraguay basins revealed no distinctive morphological features. The combined molecular and morphological results suggest that these two forms may represent cryptic species. [ABSTRACT FROM AUTHOR]

Soils in the Amazon Basin are deficient in phosphorus, essential to soil fertility. Previous studies suggested that African mineral dust deposited to Amazonian soils served as an important source of phosphorus that enhances soil fertility. These studies lacked the quantitative measurements essential to validate estimates. Here we present daily measurements of mineral dust and PM10 carried in the trade winds at Cayenne, French Guiana, during 2002–2017. MERRA‐2 model dust concentrations showed excellent agreement with measurements over this period. Consequently, we used MERRA‐2 to estimate temporal and spatial deposition rates to Amazonia. Our annual deposition rate, 8–10 Tg dust, is substantially lower than previous estimates. Deposition rates are greatest over the northern and northeastern regions of South America. In contrast, rates are low in central Amazonia. Our results raise questions about the impact of African dust on soil fertility in Amazonia. However, African aerosol transport carries other aerosol species that could play a role in soil fertility, including biomass‐burning products known to contain substantial concentrations of phosphorus. Our study highlights the need for more measurements of aerosol and precipitation chemistry over wider expanses of South America in order to better characterize aerosol chemical and physical properties, to identify aerosol sources, and to constrain model estimates. We show that over 2002–2017 dust transport to South America was negatively correlated to rainfall over the Sahel in North Africa. Long‐term monitoring is needed to capture changes in transport from Africa that might occur as a result of climate change. Plain Language Summary: The Amazon Basin plays a major role in climate by removing huge quantities of carbon dioxide (CO2) from the atmosphere and storing the carbon in vegetation. This removal partially offsets the impact of CO2 emitted by humans and the consequent rate of global warming. There is a concern about decreasing soil fertility in the Amazon Basin because of the loss of phosphorus, an essential plant nutrient, due to intense tropical weathering and biomass burning. Previous work suggested that large quantities of dust are transported from Africa to South America every year and deposited to the Amazon. Dust contains phosphorus and other nutrients that could mitigate soil losses and increase Amazonian soil fertility. However, estimates of the amount of dust carried to the Amazon are uncertain because of the lack of aerosol measurements. Our multiyear measurements of African dust in the trade winds in French Guiana, coupled with a chemical transport model, suggest that significant quantities of dust reach the heart of the Amazon Basin although the amounts are substantially less than had been previously estimated. This raises questions about the long‐term status of soil fertility in the Amazon and the future impact on the carbon cycle. We also find that the quantities of dust transported to South America are inversely linked to rainfall in North Africa. Consequently, climate change will affect dust transport to South America. Key Points: We use 15 years of aerosol measurements in trade winds at Cayenne, French Guiana, to quantify the transport of African dust to South America in boreal springDust transport may be supplying significant amounts of nutrients, including phosphorus, that are important for maintaining soil fertility in the Amazon BasinThe MERRA‐2 model yields deposition rates to the Amazon that are substantially smaller than rates from previous studies [ABSTRACT FROM AUTHOR]

Modelling continental freshwater dynamics is expected to be challenging in regions with considerable influence of multi-scale global climatic drivers. An assessment of the interplay between these climatic drivers (e.g. El-Niño Southern Oscillation-ENSO) that influence hydro-climatic conditions and hydrological processes is therefore required to optimize predictive frameworks. The main aim of this study is to assess the impacts of eleven key climate modes describing oceanic variability in the nearby oceans on the spatial and temporal distributions of terrestrial water storage (TWS) derived from Gravity Recovery and Climate Experiment (GRACE) (2002 − 2017) over South America (SA). Considering that SA accounts for nearly one-fifth of global continental freshwater discharge, this assessment is crucial because of the differences in the intrinsic response of freshwater availability in some regions to several important processes of inter-annual variability. The novel integration of independent component analysis with parameter estimation techniques in this study shows that climate variability drivers (ENSO; Southern Oscillation Index (SOI); Pacific Decadal Oscillation (PDO); Ninos 1 + 2, 3.0, 3.4 and 4.0; North Tropical Atlantic (NTA); and the Caribbean Sea Surface Temperature (SST) anomalies) have considerable association (α = 0.05) with GRACE-derived TWS over SA. The influence of Nino 4.0 (r = − 0.72), Nino 3.4 (− 0.68), Nino 3.0 (− 0.53), ENSO (r = − 0.71), PDO (r = − 0.69), SOI (r = 0.64), Caribbean SST (r = − 0.67) and NTA (r = − 0.51) on TWS are relatively stronger in tropical SA (Amazon basin/northern SA) and result in higher amplitudes of TWS (> 100 mm). Given the temporal and spatial relationships of TWS with PDO over SA, there is also evidence to suggest strong multi-decadal variability in TWS. [ABSTRACT FROM AUTHOR]

Over oceans, precipitation generally increases with warming in regions where preindustrial precipitation minus evaporation is positive. This simple "wet‐get‐wetter" principle does not hold over land. The Amazon region and Equatorial Africa currently receive ample rainfall, but the former is projected to dry out whereas precipitation is expected to increase over the latter. Our experiments with an idealized Atmospheric General Circulation Model and realistic continents show that land surface evaporation must be limited in order to obtain drying over the Amazon basin. Our simulations with rectangular, flat continents reveal that large parts of South America would receive more rainfall with warming in the absence of Africa. We suggest that this is due to a warming‐induced Matsuno‐Gill‐type circulation anomaly over Africa. We propose a new simple scaling that diagnoses precipitation change from surface relative humidity change and provides further evidence for the importance of circulation changes for future rainfall. Plain Language Summary: Comprehensive climate models project different precipitation responses to increasing CO2 levels over land compared to oceans. Maritime precipitation is projected to increase where preindustrial precipitation exceeds evaporation (such as the equatorial regions) and decrease in the subtropical oceans (where evaporation rates exceed rainfall rates). However, continental precipitation change cannot be summarized in such a simplified manner. Equatorial Africa and the Amazon basin both currently see much more rainfall than evaporation, but the Amazon region is projected to dry out in the future, whereas Central Africa will probably receive more rainfall. We find that the drying of the Amazon basin is partly caused by the increase in convection—and thus rainfall—over Equatorial Africa. The ascent of air over Africa leads to subsidence to the west of the continent, resulting in unfavorable conditions for precipitation over tropical South America and the Atlantic Ocean. Key Points: Limited evaporation from land surfaces poses a major constraint on continental precipitation change, particularly in the Amazon basinWarming‐induced circulation changes over Africa lead to a decrease in precipitation over South AmericaA new simple scaling of precipitation change provides evidence for the impact of circulation anomalies on future rainfall [ABSTRACT FROM AUTHOR]

Hemiodus bimaculatus sp. nov., is described from tributaries of the Rio Juruena and Rio Teles Pires in the upper Rio Tapajós basin. The new species is diagnosed from most congeners, except Hemiodus jatuarana, by having a conspicuous circular or horizontally elongate dark blotch on the caudal peduncle (v. inconspicuous in H. iratapuru and absent in the other species). The new species differs from H. jatuarana by having a round midlateral spot on the flank (v. absent in H. jatuarana), 98–121 perforated scales in the lateral line (v. 66–72 in H. jatuarana), 23–28 scale series above and 14–19 below lateral line (v. 12–13 above and 6–7 below in H. jatuarana). Hemiodus bimaculatus is hypothesised to be related to species of the H. microlepis group, from which it also differs by having 11–25 epibranchial (v. 26–34 in H. argenteus, 29–39 in H. microlepis, 21–42 in H. orthonops and 27–35 in H. parnaguae) and 18–31 ceratobranchial (v. 38–50 in H. argenteus, 43–58 in H. microlepis, 32–52 in H. orthonops and 34–48 in H. parnaguae) gill rakers in the first arch. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms generating species distributions remains a challenge, especially in hyperdiverse tropical forests. We evaluated the role of rainfall variation, soil gradients and herbivory on seedling mortality, and how variation in seedling performance along these gradients contributes to habitat specialisation. In a 4-year experiment, replicated at the two extremes of the Amazon basin, we reciprocally transplanted 4638 tree seedlings of 41 habitat-specialist species from seven phylogenetic lineages among the three most important forest habitats of lowland Amazonia. Rainfall variation, flooding and soil gradients strongly influenced seedling mortality, whereas herbivory had negligible impact. Seedling mortality varied strongly among habitats, consistent with predictions for habitat specialists in most lineages. This suggests that seedling performance is a primary determinant of the habitat associations of adult trees across Amazonia. It further suggests that tree diversity, currently mostly harboured in terra firme forests, may be strongly impacted by the predicted climate changes in Amazonia. [ABSTRACT FROM AUTHOR]

This synopsis provides an identification key to the genera of Tribe Lachnophorini of the Western and Eastern Hemispheres including five genera previously misplaced in carabid classifications. The genus Asklepia Liebke, 1938 is revised with 23 new species added and four species reassigned from Eucaerus LeConte, 1853 to Asklepia Liebke, 1938. In addition, a new genus is added herein to the Tribe: Peruphorticus gen. n. with its type species P. gulliveri sp. n. from Perú. Five taxa previously assigned to other tribes have adult attributes that make them candidates for classification in the Lachnophorini: Homethes Newman, Aeolodermus Andrewes, Stenocheila Laporte de Castelnau, Diplacanthogaster Liebke, and Selina Motschulsky are now considered to belong to the Lachnophorini as genera incertae sedis. Three higher level groups are proposed to contain the 18 recognized genera: the Lachnophorina, Eucaerina, and incertae sedis. Twenty-three new species of the genus Asklepia are described and four new combinations are presented. They are listed with their type localities as follows: (geminata species group) Asklepia geminata (Bates, 1871), comb. n., Santarém, Rio Tapajós, Brazil; (hilaris species group) Asklepia campbellorum Zamorano & Erwin, sp. n., 20 km SW Manaus, Brazil, Asklepia demiti Erwin & Zamorano, sp. n., circa Rio Demiti, Brazil, Asklepia duofos Zamorano & Erwin, sp. n., 20 km SW Manaus, Brazil, Asklepia hilaris (Bates, 1871), comb. n., São Paulo de Olivença, Brazil, Asklepia grammechrysea Zamorano & Erwin, sp. n., circa Pithecia, Cocha Shinguito, Perú, Asklepia lebioides (Bates, 1871), comb. n., Santarém, Rio Tapajós, Brazil, Asklepia laetitia Zamorano & Erwin, sp. n., Leticia, Colombia, Asklepia matomena Zamorano & Erwin, sp.n., 20 km SW Manaus, Brazil; (pulchripennis species group) Asklepia adisi Erwin & Zamorano, sp. n., Ilha de Marchantaria, Lago Camaleão, Brazil, Asklepia asuncionensis Erwin & Zamorano, sp. n., Asunción, Río Paraguay, Paraguay, Asklepia biolat Erwin & Zamorano, sp. n., BIOLAT Biological Station, Pakitza, Perú, Asklepia bracheia Zamorano & Erwin, sp. n., circa Explornapo Camp, Río Napo, Cocha Shimagai, Perú, Asklepia cuiabaensis Erwin & Zamorano, sp. n., Cuiabá, Brazil, Asklepia ecuadoriana Erwin & Zamorano, sp. n., Limoncocha, Ecuador, Asklepia kathleenae Erwin & Zamorano, sp. n., Belém, Brazil, Asklepia macrops Erwin & Zamorano, sp. n., Concordia, Río Uruguay, Argentina, Asklepia marchantaria Erwin & Zamorano, sp. n., Ilha de Marchantaria, Lago Camaleão, Brazil, Asklepia marituba Zamorano & Erwin, sp. n., Marituba, Ananindeua, Brazil, Asklepia paraguayensis Zamorano & Erwin, sp. n., San Lorenzo, Rio Paraguay, Paraguay, Asklepia pakitza Erwin & Zamorano, sp. n., BIOLAT Biological Station, Pakitza, Perú, Asklepia pulchripennis (Bates, 1871), comb. n., Santarém, Rio Tapajós, Brazil, Asklepia samiriaensis Zamorano & Erwin, sp. n., Boca del Río Samiria, Perú, Asklepia stalametlitos Zamorano & Erwin, sp. n., Guayamer, Río Mamoré, Bolivia, Asklepia strandi Liebke, 1938, Guyana, Asklepia surinamensis Zamorano & Erwin, sp. n., l'Hermitage, Surinam River, Surinam, Asklepia vigilante Erwin & Zamorano, sp. n., Boca del Río Samiria, Perú. Images of adults of all 18 genera are provided. [ABSTRACT FROM AUTHOR]

Although common and widespread today throughout the neotropical lowlands, the domestic dog (Canis lupus familiaris) may have been a relatively recent introduction into certain areas. Numerous early documents, however, implicate the precolumbian presence of tamed endemic South American canids, at least in lowland areas of northern South America and the adjacent Caribbean. These early and limited descriptions of small dogs that did not bark were eventually dismissed in the scholarly literature as simply domesticated dogs that were trained not to bark. A review of the earliest documentation of indigenous canids in the Spanish Main, and subsequent accounts of tamed endemic canids in various parts of the continent, suggests that native foxes or forest dogs could have been tamed. Varied sources written at different times and from different areas of lowland South America also mention interbreeding of endemic canids with domesticated dogs. The control of tamed endemic canids by indigenous populations could also have factored into the late appearance of the domestic dog, particularly in portions of the Amazon Basin. [ABSTRACT FROM AUTHOR]

Abstract: The presence of acute Chagas disease (ACD) due to oral transmission is growing and expanding in several South American countries. Within the Amazon basin, the Abaetetuba municipality has been a site of recurrent cases spanning across distinct landscapes. Because Chagas disease is primarily a zoonotic infection, we compared the enzootic Trypanosoma cruzi transmission cycles in three different environmental areas of Abaetetuba to better understand this new epidemiological situation. Philander opossum was the most abundant mammalian species collected (38% of the collected mammals) with a T. cruzi prevalence of 57%, as determined by hemocultures. Didelphis marsupialis was abundant only in the area with the higher level of environmental disturbance (approximately 42%) and did not yield detectable parasitemia. Despite similarities observed in the composition of the small mammalian fauna and the prevalence of T. cruzi infection among the studied areas, the potential of these hosts to infect vectors differed significantly according to the degree of land use (with prevalences of 5%, 41%, and 64% in areas A3, A1 and A2, respectively). Domestic mammals were also found to be infected, and one canine T. cruzi isolate was obtained. Our data demonstrated that the transmission of T. cruzi in the Amazon basin is far more complex than had been previously taught and showed that the probability of humans and domestic mammals coming into contact with infected bugs can vary dramatically, even within the same municipality. The exposure of dogs to T. cruzi infection (indicated by positive serology) was the common feature among the studied localities, stressing the importance of selecting domestic mammals as sentinels in the identification of T. cruzi transmission hotspots. [Copyright &y& Elsevier]

The article discusses a research on the species Cohniella. It presents a taxonomic revision of the species found in the Amazon River in South America. It proposes a new species found in Caatinga, Brazil called Cohniella Caatingaensis. It provides taxonomic descriptions of several species including C. Cepula, C. sprucei, and C. jonesiana.

This study describes the main circulation patterns (CP) in the Amazonian Basin over the 1975-2002 period and their relationship with rainfall variability. CPs in the Amazonian Basin have been computed for each season from the ERA-40 daily 850 hPa winds using an approach combining artificial neural network (Self Organizing Maps) and Hierarchical Ascendant Classification. A 6 to 8 cluster solutions (depending on the season considered) is shown to yield an integrated view of the complex regional circulation variability. For austral fall, winter and spring the temporal evolution between the different CPs shows a clear tendency to describe a cycle, with southern wind anomalies and their convergence with the trade winds progressing northward from the La Plata Basin to the Amazon Basin. This sequence is strongly related to eastward moving extra tropical perturbations and their incursion toward low latitude that modulate the geopotential and winds over South America and its adjoining oceans. During Austral summer, CPs are less spatially and temporally organized compared to other seasons, principally due to weaker extra tropical perturbations and more frequent shallow low situations. Each of these CPs is shown to be associated with coherent northward moving regional rainfall patterns (both in in situ data and ERA-40 reanalysis) and convective activity. However, our results reveals that precipitation variability is better reproduced by ERA-40 in the southern part of the Amazonian Basin than in the northern part, where rainfall variability is likely to be more constrained by local and subdaily processes (e.g. squall lines) that could be misrepresented in the reanalysis dataset. This analysis clearly illustrates the existing connections between the southern and northern part of the Amazonian Basin in terms of regional circulation/rainfall patterns. The identification of these CPs provide useful information to understand local rainfall variability and could hence be used to better understand the influence of these CPs on the hydrological variability in the Amazonian Basin. [ABSTRACT FROM AUTHOR]

Abstract: An ongoing controversy in Amazonian palaeoecology is the manner in which Amazonian rainforest communities have responded to environmental change over the last glacial–interglacial cycle. Much of this controversy results from an inability to identify the floristic heterogeneity exhibited by rainforest communities within fossil pollen records. We apply multivariate (Principal Components Analysis) and classification (Unweighted Pair Group with Arithmetic Mean Agglomerative Classification) techniques to floral-biometric, modern pollen trap and lake sediment pollen data situated within different rainforest communities in the tropical lowlands of Amazonian Bolivia. Modern pollen rain analyses from artificial pollen traps show that evergreen terra firme (well-drained), evergreen terra firme liana, evergreen seasonally inundated, and evergreen riparian rainforests may be readily differentiated, floristically and palynologically. Analogue matching techniques, based on Euclidean distance measures, are employed to compare these pollen signatures with surface sediment pollen assemblages from five lakes: Laguna Bella Vista, Laguna Chaplin, and Laguna Huachi situated within the Madeira-Tapajós moist forest ecoregion, and Laguna Isirere and Laguna Loma Suarez, which are situated within forest patches in the Beni savanna ecoregion. The same numerical techniques are used to compare rainforest pollen trap signatures with the fossil pollen record of Laguna Chaplin. Pollen assemblages of pollen traps situated within riparian forest communities are most similar to surface sediment samples from Lagunas Bella Vista and Chaplin. Pollen derived from terra firme forests also comprises a significant proportion of these assemblages. Together, these pollen spectra successfully identify riparian and terra firme rainforest communities surrounding the two lakes today. Close similarity between terra firme liana pollen trap assemblages and surface samples obtained from Laguna Huachi, a lake surrounded by relatively undisturbed liana forest, suggests liana forest pollen rain may also be identified within lake sediment records. Pollen spectra obtained from surface sediment samples from lakes situated within gallery forests of the Beni savanna ecoregion are significantly different to those obtained from the Madeira-Tapajós ecoregion, reflecting their different floristic compositions. By applying our findings to the previously published Laguna Chaplin Quaternary pollen record, we show that differentiation between riparian and terra firme rainforest pollen assemblages can lead to more robust and detailed palaeovegetation reconstructions than has hitherto been possible. [Copyright &y& Elsevier]

Forest burning for pastures in tropical areas represents an important component of biogeochemical cycles. In order to provide information concerning chemical modifications after forest burning, in this local study the total contents of 29 elements in topsoils were analyzed when forest is changed to pasture land. The work was carried out in 1999 in Rondoˆnia state (Brazilian Amazon Basin) focussing on a native forest site and four neighboring pastures established in 1987, 1983, 1972 and 1911 after forest conversion. Chemical fingerprint graphs of the pasture soils related to the forest soil illustrated mainly higher contents for the vast majority of macro- and micro nutrients, but for other elements as well (e.g. Ba, Sr, Cr, Ni, V or Pb). Also increases of pH levels were measured in all pastures, which remained higher than the forest values for decades. After initial increases of most of the elements in pasture of 1987 the decreases of some macro elements (e.g. C, N, K, Mg, S) in pasture 1983 as well as again the enhanced levels in pasture 1972 and 1911 suggest both a persistent leaching of these elements and a function of pasture age where external element inputs exceed outputs. Ash deposition, accumulation of organic matter, animal excreta as well as natural soil conditions are discussed as influencing factors on the element contents of the original forest and the pasture soils. Nevertheless, in this particular area continuous pasturing after forest clearing primarily enriched the soils in elements. [Copyright &y& Elsevier]

Tree-ring width chronologies of cedro (Cedrela fissilis Vell.) (1875 to 2018), jatobá (Hymenaea courbaril L.) (1840 to 2018) and roxinho Peltogyne paniculata Benth.) (1910 to 2018) were developed by dendrochronological techniques in the southern Amazon Basin. Acceptable statistics for the tree-ring chronologies were obtained, and annual calendar dates were assigned. Due to the lack of long-term chronologies for use in paleoclimate reconstructions in degraded forest areas, dendrochronological dating was validated by 14C analysis. Tree-rings selected for analysis corresponded to 1957, 1958, 1962, 1963, 1965, 1971, and 1972. Those are critical calendar years in which atmospheric 14C changes were the highest, and therefore their tree-ring cellulose extracts 14C signatures when in alignment with existing post-AD 1950 atmospheric 14C atmospheric curves would indicate annual periodicity. Throughout our correlated calendar years and post-AD 1950 14C signatures, we indicate that H. courbaril shows an erratic sequence of wood ages. The other two tree species, C. fissilis and P. paniculata, are annual in nature and can be used successfully as paleoclimate proxies. Moreover, due to the sampling site's strategic location in relation to the Tropical Low-Pressure Belt over South America, these trees can be used to enhance the limited amount of observational data in Southern Hemisphere atmospheric 14C calibration curves. [ABSTRACT FROM AUTHOR]

The Santa Rosa fossil locality in eastern Perú produced the first Paleogene vertebrate fauna from the Amazon Basin, including the oldest known monkeys from South America. This diverse paleofauna was originally assigned an Eocene age based largely on the stage of evolution of the site's caviomorph rodents and marsupials. Here, we present detrital zircon dates that indicate that the maximum composite age of Santa Rosa is 29.6 ± 0.08 Ma (Lower Oligocene), although several zircons from Santa Rosa date to the Upper Oligocene. The first appearance datum for Caviomorpha in South America is purported to be the CTA-27 site in the Contamana region of Perú, which is hypothesized to be ∼41 Ma (Middle Eocene) in age. However, the presence of the same caviomorph species and/or genera at both CTA-27 and at Santa Rosa is now difficult to reconcile with a >11-My age difference. To further test the Middle Eocene age estimate for CTA-27, we ran multiple Bayesian tip-dating analyses of Caviomorpha, treating the ages of all Paleogene species from Perú as unknown. These analyses produced mean age estimates for Santa Rosa that closely approximate the maximum 29.6 ± 0.08 Ma composite date provided by detrital zircons, but predict that CTA-27 is much younger than currently thought (∼30 Ma). We conclude that the ∼41 Ma age proposed for CTA-27 is incorrect, and that there are currently no compelling Eocene records of either rodents or primates in the known fossil record of South America., Competing Interests: The authors declare no competing interest.

Peacock bass Cichla ocellaris is a piscivorous cichlid native from the Amazon and Orinoco river basins, which has been broadly introduced into tropical areas worldwide, leading to several adverse local effects. However, predictors of its invasibility and assessments of its ecological impacts over large spatial scales are still lacking. The importance of different environmental factors in explaining the relative abundance of peacock bass in 62 sites across South America (30 native and 32 invaded systems) was investigated. The impacts of peacock bass on fish assemblages were appraised, using years since introduction as a proxy of its cumulative impacts and modern statistical techniques, such as random forests, and negative binomial regression models. Random forests highlighted maximum depth, introduced status, and ecosystem type as the best predictors of the peacock bass relative abundance, which ranged 0.01-26.0%, increased with maximum depth, was highest in invaded reservoirs but decreased with depth in native riverine populations. Other factors such as climate or limnological features were less important in explaining C. ocellaris abundance, which did not vary markedly with years since introduction. Introduction year was not related to latitude but varied among hydrographic regions, indicating invasion pathways not linked to geographical proximity. Variation partitioning of different fish assemblage metrics showed that hydrographic region followed by limnological and reservoir features accounted for most explained variation, indicating a strong historical and local influence. Introduction time accounted for 5-8% of variation in species composition and diversity, independently of limnological features. Our results suggest that the ecological effects of introduced C. ocellaris on native fish fauna are likely but small compared to large geographical and environmental gradients. Although experiments and before-after designs are probably more sensitive in detecting the ecological impacts of invasive species, large-scale compilations of available data are more feasible and can provide invaluable information, especially for large-sized invaders that are often illegally introduced., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

• Combined JADE rotation and PLSR model to predict TWS over South America. • Climate variability and exchange of fluxes within floodplain drive TWS in the Amazon. • GRACE hydrological signals in some South American regions are complex. • Rainfall appear not to be the key driver of TWS in some regions of South America. • PLSR outputs indicate TWS in some river basins are less associated with climate. The underlying uncertainties in the prediction of freshwater evolutions in some regions can be induced by several unmitigated human actions, multi-scale climatic drivers, and dynamic physical processes. These factors have enduring hydro-ecological effects on the environments and combine to limit our understanding of large scale hydrological processes and impacts of climate on water availability. Considering the fact that several hydrogeological perturbations and disturbances have been reported during the last decade in South America (SA), a further assessment of continental land water storage is therefore warranted. In this study, a two-step regularization approach that combined the JADE (Joint Approximate Diagonalisation of Eigen matrices) algorithm and PLSR (partial least squares regression) was employed to assess GRACE (Gravity Recovery and Climate Experiment)-terrestrial water storage (TWS) over SA. Based on the Bartlett's statistics, significant independent patterns of SST (Sea Surface Temperature) anomalies from the Pacific and Atlantic oceans were used in the PLSR scheme to model the temporal evolutions of TWS (2002 - 2017) over twelve prominent river basins in SA. From the JADE rotation of TWS over SA, strong inter-annual changes in TWS observed over the Amazon basin and within its floodplain corridors were identified. The unabated mass loss in Patagonia ice-field caused by warming of the climate and other GRACE-hydrological signals were also retrieved from the JADE scheme. The rainfall-TWS relationship is considerably strong (r = 0.80 at 0 - 2 months lag) in much of tropical SA, including the Amazon basin and highlights the influence of climate variability in the region. Medium (r = 0.40) and moderately strong (r = 0.60) rainfall-TWS relationship were also found to be significant (α = 0.05) but with up to 4 months lag and more in some basins. During the 2010 - 2017 period, estimated TWS trends (α = 0.05) showed a considerable fall in Orinoco (- 38.48 ± 7.90 mm/yr) and Sao Francisco (- 30.84 ± 4.17) while the strongest rise was found in Uruguay (28.28 ± 3.49 mm/yr). As the rainfall-TWS relationship is not statistically significant (α = 0.05) in some areas, the spatial distribution of trends in TWS and rainfall, especially in some arid regions, which are inconsistent confirm possible impacts resulting from complex hydrogeological processes and/or anthropogenic influence. Further, in the modelling of TWS time series using the JADE-PLSR scheme, several validation skill metrics (e.g., R 2 , Nash-Sutcliffe Efficiency) confirm the considerable agreements between predicted and observed TWS in the Amazon ( R 2 = 0.95), Orinoco ( R 2 = 0.94), Tocantins ( R 2 = 0.91), and Chobut ( R 2 = 0.88). However, GRACE-hydrological signals in some regions are somewhat complex given the relatively higher uncertainties in the multivariate models employed in this study. [ABSTRACT FROM AUTHOR]

The deposition of phosphorus (P) from African dust is believed to play an important role in bolstering primary productivity in the Amazon Basin and Tropical Atlantic Ocean (TAO), leading to sequestration of carbon dioxide. However, there are few measurements of African dust in South America that can robustly test this hypothesis and even fewer measurements of soluble P, which is readily available for stimulating primary production in the ocean. To test this hypothesis, we measured total and soluble P in long-range transported aerosols collected in Cayenne, French Guiana, a TAO coastal site located at the northeastern edge of the Amazon. Our measurements confirm that in boreal spring when African dust transport is greatest, dust supplies the majority of P, of which 5% is soluble. In boreal fall, when dust transport is at an annual minimum, we measured unexpectedly high concentrations of soluble P, which we show is associated with the transport of biomass burning (BB) from southern Africa. Integrating our results into a chemical transport model, we show that African BB supplies up to half of the P deposited annually to the Amazon from transported African aerosol. This observational study links P-rich BB aerosols from Africa to enhanced P deposition in the Amazon. Contrary to current thought, we also show that African BB is a more important source of soluble P than dust to the TAO and oceans in the Southern Hemisphere and may be more important for marine productivity, particularly in boreal summer and fall., Competing Interests: The authors declare no conflict of interest.

Forest dynamics and tree species composition vary substantially between Paleotropical and Neotropical forests, but these broad biogeographic regions are treated uniformly in many land models. To assess whether these regional differences translate into variation in productivity and carbon (C) storage, we compiled a database of climate, tree stem growth, litterfall, aboveground net primary production (ANPP), and aboveground biomass across tropical rainforest sites spanning 33 countries throughout Central and South America, Asia, and Australasia, but excluding Africa due to a paucity of available data. Though the sum of litterfall and stem growth (ANPP) did not differ between regions, both stem growth and the ratio of stem growth to litterfall were higher in Paleotropical forests compared to Neotropical forests across the full observed range of ANPP. Greater C allocation to woody growth likely explains the much larger aboveground biomass estimates in Paleotropical forests (~29%, or ~80 Mg DW/ha, greater than in the Neotropics). Climate was similar in Paleo- and Neotropical forests, thus the observed differences in C likely reflect differences in the evolutionary history of species and forest structure and function between regions. Our analysis suggests that Paleotropical forests, which can be dominated by tall-statured Dipterocarpaceae species, may be disproportionate hotspots for aboveground C storage. Land models typically treat these distinct tropical forests with differential structures as a single functional unit, but our findings suggest that this may overlook critical biogeographic variation in C storage potential among regions., (© 2019 by the Ecological Society of America.)

Anopheles darlingi is the main malaria vector in humans in South America. In the Amazon basin, it lives along the banks of rivers and lakes, which responds to the annual hydrological cycle (dry season and rainy season). In these breeding sites, the larvae of this mosquito feed on decomposing organic and microorganisms, which can be pathogenic and trigger the activation of innate immune system pathways, such as proteins Gram-negative binding protein (GNBP). Such environmental changes affect the occurrence of polymorphic inversions especially at the heterozygote frequency, which confer adaptative advantage compared to homozygous inversions. We mapped the GNBP probe to the An. darlingi 2Rd inversion by fluorescent in situ hybridization (FISH), which was a good indicator of the GNBP immune response related to the chromosomal polymorphic inversions and adaptative evolution. To better understand the evolutionary relations and time of divergence of the GNBP of An. darlingi, we compared it with nine other mosquito GNBPs. The results of the phylogenetic analysis of the GNBP sequence between the species of mosquitoes demonstrated three clades. Clade I and II included the GNBPB5 sequence, and clade III the sequence of GNBPB1. Most of these sequences of GNBP analyzed were homologous with that of subfamily B, including that of An. gambiae (87 %), therefore suggesting that GNBP of An. darling belongs to subfamily B. This work helps us understand the role of inversion polymorphism in evolution of An. darlingi.

Above-ground dry biomass of living trees including palms was estimated in 65 1ha plots spanning a 1000km2 landscape in centralAmazonia. The study area was located on heavily weathered, nutrient-poor soils that are widespread in the Amazon region. Biomass values were derived by measuring the diameter-at-breast-height (DBH) of all >/=10cm trees in each plot, then using an allometric equation and correction factor for small trees to estimate total tree biomass. Detailed information on soil texture, organic carbon, available water capacity, pH, macro- and micro-nutrients, and trace elements was collected from soil surface samples (0-20cm) in each plot, while slope was measured with a clinometer. Biomass estimates varied more than two-fold, from 231 to 492 metric tons ha-1, with a mean of 356+/-47 tons ha-1. Simple correlations with stringent (p<0.006) Bonferroni corrections suggested that biomass was positively associatedwith total N, total exchangeable bases, K+, Mg2+, clay, and organic C in soils, and negatively associated with Zn+, aluminum saturation, and sand. An ordination analysis revealed one major and several minor soil gradients in the study area, with the main gradient discriminating sites with varying proportions of clay (with clayey soils having higher concentrations of total N, organic C, most cations, and lower aluminum saturation and less sand). A multiple regression analysis revealed that the major clay-nutrient gradient was the only significant predictor, with the model explaining 32.3% of the total variation in biomass. Results of the analysis suggest that soil-fertility parameters can account for a third or more of the variation in above-ground biomass in Amazonian terra-firme forests. We suggest that, because the conversion of forest to pasture tends to reduce the nitrogen, clay, organic carbon, and nutrient contents of soils, forests that regenerate on formerly cleared lands may have [ABSTRACT FROM AUTHOR]