23736 research outputs found
Sort by
Linking dissolved organic matter composition and bacterioplankton communities in an Amazon floodplain system
No full textDissolved organic matter (DOM) is the main substrate for aquatic prokaryotes, fuelling their metabolism and controlling community composition. Amazonian rivers transport and process large fluxes of terrestrial DOM, but little is known about the link between DOM composition and heterotrophic bacteria in the Amazon basin. The aims of this study were to characterize DOM composition and investigate the coupling between DOM and bacterial community composition (BCC) during a complete hydrological cycle in an Amazon floodplain system (lake Janauacá). Our study revealed a clear seasonal pattern in DOM composition through the flood pulse, which affected the amounts of autochthonous and allochthonous inputs and consequently the extent of humification, molecular weight, and aromaticity of the DOM. BCC was tightly coupled to DOM fluorescence, which was also driven by differences over the hydrological cycle, with distinct components and operational taxonomic units being simultaneously more abundant and correlating with a specific season. This coupling was particularly well reflected for three of the four identified fluorescence components, two terrestrial humic-like components (C1 and C3) and an autochthonous component (C4). Despite clear changes in DOM composition, dissolved organic carbon concentrations tended to be relatively stable throughout the year. Overall, our results suggest that BCC shifts were associated with DOM quality but not with its quantity (that remains relatively constant throughout the year), and that bacteria preferably use labile and freshly produced DOM in lake Janauacá. © 2019 Association for the Sciences of Limnology and Oceanograph
The combined role of dispersal and niche evolution in the diversification of Neotropical lizards
No full textEcological requirements and environmental conditions can influence diversification across temporal and spatial scales. Understanding the role of ecological niche evolution under phylogenetic contexts provides insights on speciation mechanisms and possible responses to future climatic change. Large-scale phyloclimatic studies on the megadiverse Neotropics, where biomes with contrasting vegetation types occur in narrow contact, are rare. We integrate ecological and biogeographic data with phylogenetic comparative methods, to investigate the relative roles of biogeographic events and niche divergence and conservatism on the diversification of the lizard genus Kentropyx Spix, 1825 (Squamata: Teiidae), distributed in South American rainforests and savannas. Using five molecular markers, we estimated a dated species tree, which recovered three clades coincident with previously proposed species groups diverging during the mid-Miocene. Biogeography reconstruction indicates a role of successive dispersal events from an ancestral range in the Brazilian Shield and western Amazonia. Ancestral reconstruction of climatic tolerances and niche overlap metrics indicates a trend of conservatism during the diversification of groups from the Amazon Basin and Guiana Shield, and a strong signal of niche divergence in the Brazilian Shield savannas. Our results suggest that climatic-driven divergence at dynamic forest-savanna borders might have resulted in adaptation to new environmental niches, promoting habitat shifts and shaping speciation patterns of Neotropical lizards. Dispersal and ecological divergence could have a more important role in Neotropical diversification than previously thought. © 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd
Diversidade Microbiana da Amazônia Vol. 3
Full text linkAo divulgar o terceiro volume do livro Diversidade Microbiana da Amazônia, tendo como conteúdo,
cerca de 65% dos trabalhos apresentados no 7° CDMicro – Congresso sobre Diversidade Microbiana da
Amazônia - realizado no final de 2018 na cidade de Manaus, queremos agradecer aos participantes, todo
o apoio dado ao nosso evento.
O CDMicro vem, ao longo desses anos, contribuindo para a divulgação e troca de informações sobre
a microbiota, com ênfase à presente na Amazônia brasileira, e já se consolidou na região, servindo como
referência para os alunos, professores e pesquisadores que trabalham com os microrganismos encontrados na natureza.
O livro é o coroamento do processo de divulgação da maior parte do conhecimento apresentado no
congresso e fica à disposição a todos os interessados.
Esperamos com essa obra, estar contribuindo para que as informações sobre os microrganismos sejam mais intensamente compartilhadas entre todos aqueles que se dedicam a conhecê-los melhor
Propagação vegetativa de Himatanthus sucuuba (Spruce ex Müll. Arg.) Woodson por meio das técnicas de estaquia e embriogênese somática
Full text linkVegetative propagation techniques, such as cutting and somatic embryogenesis, can be an advantageous alternative to the production of native species seedlings with social-environmental and economic importance as Himatanthus sucuuba. In this context, the present study aimed to evaluate the effect of different types of cuttings and indole butyric acid (IBA) concentration, on the survival and rooting of cuttings of H. sucuuba, as well as to induce somatic embryogenesis in callus originating from nodal and foliar segments in different cultivation conditions. In the cuttings, the experimental design used was in randomized complete blocks, with a factorial arrangement: 2 types of cuttings (with and without leaves) and 3 concentrations of IBA (0, 1000 and 3000 mg L–1). After 100 days, were evaluated the following variables: survival (%), rooting (%), number of roots per cutting, length of the largest root (cm), number of leaves and dry biomass. The somatic embryogenesis experiment was subdivided into three distinct phases: induction (I), maturation (II) and germination of somatic embryos (III). In phase I, the explants' responses to callus formation in MS medium, with 2,4-dichlorophenoxyacetic acid (2.4-D) and Thidiazuron (TDZ) (18.08+9.8 μM and 4.52+6.81 μM), were evaluated using descriptive statistics. In phase II, the effects of abscisic acid (ABA) on the formation of embryogenic structures in the callus were evaluated, in MS and B5 medium, with and without the addition of activated carbon. And in phase III, the potential for conversion of embryos to seedlings in B5 medium supplemented with IBA+BAP (6-benzylaminopurine). The design used in the last two phases was completely randomized, with a 2x2x4 and 2x2x2 factorial arrangement, respectively: 2 explants (nodal and leaf segment callus), 2 light conditions (white and dark light), 4 concentrations of ABA (0, 10, 20 and 30 μM) or 2 concentrations of AIB+BAP (1+2.5 μM and 1+5 μM). The data were subjected to analysis of variance (ANOVA) and means compared by Tukey’s test at p<0.05. As for the percentage of survival and rooting of cuttings, average values above 70% were observed in all treatments. There was no significance for the interaction of the factors analyzed, neither for the effect of AIB, analyzed in isolation. The cutting of H. sucuuba was considered viable, and the maintenance of the leaves, associated with juvenility of the propagules, were determining factors in the conditions in which this study was developed. The results obtained for somatic embryogenesis demonstrate a double interaction between the type of explant and the luminosity and absence of significant
differences for ABA. Despite the success in callus induction, the following maturation and germination protocols were ineffective for obtaining seedlings using this technique. New studies must be carried out in order to intensify the expression of somatic embryogenesis, bypass the phenolic oxidation of the culture and increase the rooting and survival percentages in the cutting technique.As técnicas de propagação vegetativa, tais como a estaquia e a embriogênese somática, podem ser alternativas vantajosas para a produção de mudas de espécies nativas com importância socioambiental e econômica, como Himatanthus sucuuba. Neste contexto, o presente estudo teve como objetivo avaliar o efeito de diferentes tipos de estacas e concentrações de ácido indolbutírico (AIB), sobre a sobrevivência e enraizamento das estacas de H. sucuuba, bem como, induzir a embriogênese somática em calos originados a partir de segmentos nodais e foliares em diferentes condições de cultivo. Na estaquia, o delineamento experimental utilizado foi em blocos casualizados, com arranjo fatorial duplo: 2 tipos de estacas (com e sem folhas) e 3 concentrações de AIB (0, 1000 e 3000 mg L–1). Após 100 dias, foram avaliadas as seguintes variáveis: sobrevivência (%), enraizamento (%), número de raízes por estaca, comprimento da maior raiz (cm), número de folhas e biomassa seca. O experimento da embriogênese somática foi subdividido em três fases distintas: indução (I), maturação (II) e germinação de embriões somáticos (III). Na fase I foram avaliadas as respostas dos explantes quanto à formação de calos em meio MS, com ácido diclorofenoxiacético (2,4-D) e Tidiazuron (TDZ) (18,08+9,8 μM e 4,52+6,81 μM), por meio de estatística descritiva. Na fase II, foi avaliado os efeitos do ácido abscísico (ABA) sobre a formação de estruturas embriogênicas nos calos, em meio MS e B5, com e sem a adição de carvão ativado. E na III, o potencial de conversão de embriões a plântulas, em meio B5 suplementado com AIB+BAP (6-benzilaminopurina). O delineamento utilizado nas duas últimas fases foi o inteiramente casualizado, com arranjo fatorial 2x2x4 e 2x2x2, respectivamente: 2 explantes (calos de segmentos nodais e foliares), 2 condições de luminosidade (luz branca e escuro), 4 concentrações de ABA (0, 10, 20 e 30 μM) ou 2 concentrações de AIB+BAP (1+2,5 μM e 1+5 μM). Os dados foram submetidos a análise de variância (ANOVA), e tiveram suas médias comparadas entre si, pelo teste de Tukey a p<0,05. Quanto aos percentuais de sobrevivência e enraizamento das estacas, foram observados valores médios superiores a 70% em todos os tratamentos. Não houve significância para a interação dos fatores analisados, tampouco para o efeito do AIB, analisado isoladamente. A estaquia de H. sucuuba foi considerada viável, sendo que a manutenção das folhas, associada a juvenilidade dos propágulos, foram fatores determinantes nas condições
em que o presente estudo foi desenvolvido. Já os resultados obtidos para embriogênese somática, demonstram uma interação dupla entre o tipo de explante e a luminosidade, e ausência de diferenças significativas para o ABA. Apesar do sucesso na indução de calos, os protocolos seguintes de maturação e germinação foram ineficazes para a obtenção de plântulas por meio desta técnica. Novos estudos devem ser realizados no sentido de intensificar a expressão da embriogênese somática, a fim de controlar a oxidação fenólica da cultura e aumentar os percentuais de enraizamento e sobrevivência na técnica de estaquia
Phylogenomics and biogeography of the world's thrushes (Aves, Turdus): New evidence for a more parsimonious evolutionary history
Full text linkTo elucidate the relationships and spatial range evolution across the world of the bird genus Turdus (Aves), we produced a large genomic dataset comprising ca 2 million nucleotides for ca 100 samples representing 53 species, including over 2000 loci. We estimated time-calibrated maximum-likelihood and multispecies coalescent phylogenies and carried out biogeographic analyses. Our results indicate that there have been considerably fewer trans-oceanic dispersals within the genus Turdus than previously suggested, such that the Palaearctic clade did not originate in America and the African clade was not involved in the colonization of the Americas. Instead, our findings suggest that dispersal from the Western Palaearctic via the Antilles to the Neotropics might have occurred in a single event, giving rise to the rich Neotropical diversity of Turdus observed today, with no reverse dispersals to the Palaearctic or Africa. Our large multilocus dataset, combined with dense species-level sampling and analysed under probabilistic methods, brings important insights into historical biogeography and systematics, even in a scenario of fast and spatially complex diversification. © 2020 The Author(s) Published by the Royal Society. All rights reserved
New species from the nivicola group of Hypogastrura Bourlet, 1839 (Collembola, Poduromorpha, Hypogastruridae) from Canada
No full textA new Hypogastrura species of the nivicola group from Canada is described and illustrated. The new species is characterized by postantennal organ with outer anterior lobe elongated, head interocular tubercles not prominent, all terga with some extra chaetae, dens dorsally with 8-9 conical, bi- or tridentate spines, and a boat-shaped mucro with subapical tooth. A discussion on the morphology of the nivicola group is given and an identification key for all eight species of this group found in the Nearctic is provided. Copyright © 2020 Magnolia Pres
Hierarchical effects of historical and environmental factors on lizard assemblages in the upper Madeira River, Brazilian Amazonia
Full text linkInvestigating the role of historical and ecological factors structuring assemblages is relevant to understand mechanisms and processes affecting biodiversity across heterogeneous habitats. Considering that community assembly often involves scale-dependent processes, different spatial scales may reveal distinct factors structuring assemblages. In this study we use arboreal and leaf-litter lizard abundance data from 83 plots to investigate assemblage spatial structure at two distinct scales in southwestern Brazilian Amazonia. At a regional scale, we test the general hypothesis that the Madeira River acts as a barrier to dispersal of some lizard species, which results in distinct assemblages between river banks. At a local scale, we test the hypothesis that assemblages are not evenly distributed across heterogeneous habitats but respond to a continuum of inadequate-to-optimal portions of environmental predictors. Our results show that regional lizard assemblages are structured by the upper Madeira River acting as a regional barrier to 29.62% of the species sampled. This finding suggests species have been historically isolated at one of the river banks, or that distinct geomorphological features influence species occurrence at each river bank. At a local scale, different sets of environmental predictors affected assemblage composition between river banks or even along a river bank. These findings indicate that environmental filtering is a major cause of lizard assemblage spatial structure in the upper Madeira River, but predictor variables cannot be generalized over the extensive (nearly 500 km) study area. Based on a single study system we demonstrate that lizard assemblages along the forests near the banks of the upper Madeira River are not randomly structured but respond to multiple factors acting at different and hierarchical spatial scales. © 2020 Marques Peixoto et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
The influence of the atlantic multidecadal oscillation on the choco low-level jet and precipitation in colombia
No full textThis study examines the influence of the Atlantic Multidecadal Oscillation (AMO) on the Choco Low-level Jet (CJ) variations during the 1983-2016 period. Considering the September-November (SON) 925 hPa zonal wind index in the CJ core, a significant breakpoint occurs in 1997 with larger values after 1997. The changes in the CJ and Caribbean Low-Level Jet (CLLJ), and their related ocean-atmospheric patterns and impacts on precipitation over Colombia were analyzed considering separately the 1983-1996 and 1998-2016 periods, which overlap the cold and warm AMO phases, respectively During the 1998-2016 period, the negative sea surface temperature (SST) anomalies in the tropical Pacific Ocean and the positive ones in the Caribbean Sea and Tropical North Atlantic (TNA) strengthen the CJ and weaken the CLLJ, and moisture is transported into Central and Western Colombia increasing the rainfall there. Our results indicate that part of the CJ strengthening after 1997 was due to a higher percentage of intense CJ events coinciding with La Nina events during the warm AMO and cold Pacific Decadal Oscillation (PDO) background. However, the AMO-related SST and sea level pressure (SLP) variations in the TNA seem to be more crucial in modulating the CJ and CLLJ intensities, such that CJ is weakened (intensified) and CLLJ is intensified (weakened) before (after) 1997. As far as we know, the relations of the CJ and CLLJ intensities to the AMO phases were not examined before and might be useful for modeling studies. © 2020 by the authors
Unveiling geographical gradients of species richness from scant occurrence data
No full textAim: Despite longstanding investigation, the gradients of species richness remain unknown for most taxa because of shortfalls in knowledge regarding the quantity and distribution of species. Here, we explore the ability of a geostatistical interpolation model, regression-kriging, to recover geographical gradients of species richness. We examined the technique with an in silico gradient of species richness and evaluated the effect of different configurations of knowledge shortfalls. We also took the same approach for empirical data with large knowledge gaps, the infraorder Furnariides of suboscine birds. Innovation: Regression-kriging builds upon two cornerstones of geographical gradients of biodiversity, the spatial autocorrelation of species richness and the conspicuous association of species with environmental factors. With this technique, we recovered a simulated gradient of richness using < 0.01% of sampling sites across the region. The accuracy of the regression-kriging is higher when input samples are more evenly distributed throughout the geographical space rather than the environmental space of the target region. Moreover, the accuracy of this method is more sensitive to the sufficiency of sampling effort within cells than to the quantity of sampled localities. For Furnariides birds, regression-kriging provided a geographical gradient of species richness that resembles purported patterns of other groups and illustrated ubiquitous shortfalls of knowledge about bird diversity. Main conclusions: Geostatistical interpolation, such as regression-kriging, might be a useful tool to overcome shortfalls in knowledge that plague our understanding of geographical gradients of biodiversity, with many applications in ecology, palaeoecology and conservation. © 2020 John Wiley & Sons Lt