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Integrative taxonomy reveals a new species of Pacu (Characiformes: Serrasalmidae: Myloplus) from the Brazilian Amazon [Integrative taxonomy reveals a new species of Pacu (Characiformes: Serrasalmidae: Myloplus) from the Brazilian Amazon]
No full textPacus of the genus Myloplus represent a formidable taxonomic challenge, and particularly so for the case of M. asterias and M. rubripinnis, two widespread and common species that harbor considerable morphological diversity. Here we apply DNA barcoding and multiple species discovery methods to find candidate species in this complex group. We report on one well-supported lineage that is also morphologically and ecologically distinct. This lineage represents a new species that can be distinguished from congeners by the presence of dark chromatophores on lateral-line scales, which gives the appearance of a black lateral line. It can be further diagnosed by having 25–29 branched dorsal-fin rays (vs. 18–24), 89–114 perforated scales from the supracleithrum to the end of hypural plate (vs. 56–89), and 98–120 total lateral line scales (vs. 59–97). The new species is widely distributed in the Amazon basin, but seems to have a preference for black-and clearwater habitats. This ecological preference and black lateral line color pattern bears a striking similarity to the recently described silver dollar Metynnis melanogrammus. © 2020 The Authors
Dams, Chinese investments, and EIAs: A race to the bottom in South America?
No full textThe political economy of dam development in South America is changing as a result of a resurgence in water infrastructure investments. The arrival of Chinese-funded projects in the region has altered a context traditionally dominated by multilateral development banks. Tensions are escalating around new dam projects and the environmental impact assessment process is increasingly the site of politicization around water in the region. In this perspective, we examine the most recent surge in dam development in South America, the resulting environmental and social impacts, and the mobilization of civil society and environmental groups that have developed in response to these projects. In the absence of regionally shared standards for environmental assessment and regional mechanisms to mitigate the emerging conflicts—primarily occurring between companies, states, and civil society—we argue there is a risk of a race to the bottom to finance infrastructure projects with laxer environmental and social standards. © 2019, Royal Swedish Academy of Sciences
Compreendendo os efeitos de características topoedáficas sobre a produtividade do sítio em plantios de Bertholletia excelsa Bonpl. no Amazonas
Get PDFForest site classification is a crucial prerequisite for species selection and definition of management strategies in productive plantations. However, even for the most widely planted native forest species in Amazonia, such as Brazil nut (Bertholletia excelsa Bonpl.), the site quality still is little known. Here, we ask if the variation in soil quality and topography influences the site productivity in B. excelsa plantations. Nonlinear models were tested to classify the productive capacity of B. excelsa stands of different ages (14 to 21 years), from the algebraic difference method. We used a database of 75 temporary plots allocated on field and complete stem analysis of 30 trees. Chemical and physical soil analysis were realized at depths of 0-20 cm and 20-40 cm. Topographic information was obtained by GPS and digital elevation model image processing provided by Shuttle Radar Topography Mission (SRTM). Site classes were spatialized in the study area using the geostatistical interpolation method by ordinary point kriging. The relationships between topoedaphic variables and site index were evaluated by correlation matrix to identify the major characteristics limiting the site quality. In addition, regression models were adjusted to evaluate whether edaphic and topographical characteristics explain the growth variation in B. excelsa stands, with the identification of the best predictors by principal component analysis and stepwise backward method. The Chapman-Richards model presented a good statistical performance, a good distribution of residues and resulted in polymorphic curves that best represented the behavior of the dominant height variable over time. The polymorphism evaluation indicated a differentiated growth patterns among the sites. Soil texture (sand content) and topography (altitude) were the main drivers of site productivity. However, some chemical variables of the soil (K+, Mn2+ and pHKCl) also contributed to explaining the variation in the site productivity. The results can support the best planning of operational activities related to installation and management of B. excelsa stands in the Amazon, besides to identification of potential areas to expand the plantations of this important commercial tree species.A classificação de sítios florestais é pré-requisito para a seleção de espécies e definição de estratégias de manejo de povoamentos florestais. No entanto, mesmo para as espécies florestais nativas mais plantadas na região amazônica, a exemplo da Castanheira da amazônia (Bertholletia excelsa Bonpl.), a variação na qualidade dos sítios é pouco conhecida. O objetivo geral deste estudo foi verificar se a variação na qualidade do solo e topografia influencia a produtividade do sítio em plantios de B. excelsa. Foram comparados diferentes modelos não-lineares para classificar a capacidade produtiva de povoamentos de B. excelsa de diferentes idades (14 a 21 anos) localizados no município de Itacoatiara, Amazonas. Para tanto, utilizamos o método da diferença algébrica aplicado a um banco de dados oriundo de 75 parcelas temporárias e da análise completa de tronco de 30 árvores. Em campo, foram feitas medições de resistência do solo à penetração e coletadas amostras de solo nas profundidades de 0-20 cm e 20-40 cm para análises química e física do solo. As informações topográficas foram obtidas a partir de GPS e processamento de imagens de modelo digital de elevação da Shuttle Radar Topography Mission (SRTM). Os modelos Schumacher, Chapman-Richards, Bailey-Clutter, Logístico, Gompertz e Hossfeld IV foram comparados usando estatísticas de erro padrão da estimativa em porcentagem, critério de Informação de Akaike, critério de Informação Bayesiano, análise gráfica dos resíduos e estabilidade entre as curvas polimórficas e anamórficas de cada modelo. As classes de sítio foram espacializadas na área de estudo usando o método de interpolação geoestatística por krigagem ordinária pontual. As relações entre as variáveis topoedáficas e os índices de sítio foram testadas por matriz de correlação e análise de componentes principais para identificar as características mais limitantes à produtividade do sítio. Modelos de regressão múltipla foram ajustados para avaliar se características topoedáficas explicam a variação de crescimento nos povoamentos florestais de B. excelsa. O modelo Chapman-Richards apresentou bom desempenho estatístico, boa distribuição de resíduos e resultou em curvas polimórficas que melhor representaram o comportamento da variável altura dominante em função da idade dos plantios. A avaliação do polimorfismo indicou padrão de crescimento diferenciado entre os sítios. As diferenças na capacidade produtiva dos sítios foram relacionadas principalmente à textura do solo e topografia. A variação na qualidade do sítio em povoamentos de B. excelsa foi explicada principalmente por características físicas do solo como teor de areia, altitude e, em menor magnitude, por características químicas como K+, Mn2+ e pHKCl. Os resultados encontrados deverão subsidiar futuras ações de planejamento de atividades operacionais relacionadas às etapas de implantação e condução dos povoamentos de B. excelsa no Amazonas, além de contribuir para a identificação de áreas potenciais à expansão de plantios desta espécie
The Upper Madeira River sub-basin suspended sediment connectivity system. A brief hydro-climatological approach assessment.
No full textWith a contribution of ~ 50% of the total suspended sediment load to the Amazon River, the Madeira River has a key role in sustaining the major fluvial system. This high contribution has its origin in the complex Andes geology, and the interaction with different erosive factors. Particularly, the rainfall plays an important role in the sediment dynamic. Hence, this work presents the analysis that was done in the Upper Madeira sub-basin relating the spatiotemporal rainfall variability with the water discharge and the suspended sediment concentration. Through the assessment of the fine fraction of the suspended sediment at the outlet of the principal tributaries -Beni and Mamoré rivers-, it was found that a decrease of suspended sediment concentration, downstream the Hydroelectric Madeira Complex (Jiraú and Santo Antonio dams) at the station of Porto Velho in Brazil is partially related to a decrease of sediment, upstream the dams in the Beni River. Yet, the existence of different hypothesis related to the decrease, as well as the limited data available at the Andean Madre de Dios River and middle sub-basin, made unable to conclude with confidence the main reason for the decrease. One of the hypothesis, was the change in the spatiotemporal rainfall variability that could limited the sediment in the river. Therefore, considering that the station of Rurrenabaque in the Andean Beni River, represents nearly 60% of the suspended sediment at the outlet of the river (Vauchel et al. 2017), the rainfall, water discharge and suspended sediment concentration relationships were evaluated. The main cause related to the decrease was also not well described only by the assessment at Rurrenabaque, however, the evaluation between the surface and base flow with the suspended sediment concentration, showed the dual role rainfall has on the suspended sediment dynamics, firstly promoting solid material detachment and mobilization it to the river channel by the surface flow and, secondly through the groundwater recharge it promotes the dilution of the sediment concentration. The former allowed the estimation of suspended sediment concentration based on a water discharge seasonal empirical function that was further compare with a probabilistic estimation (Copula functions). As described above the key role the rainfall has on the suspended sediment dynamic and to be able to have a rainfall validated data set to assess variable relationships, the satellite-based precipitation product CHIRP in its second version was validated according the main modes of rainfall variability in the sub-basin, particularly at its Andean region.O Rio Madeira tem um papel fundamental na sustentação do grande sistema fluvial do rio
Amazonas, com uma contribuição aproximada do 50% da carga total de sedimentos em
suspensão. Este grande aporte tem sua origem na complexa geologia dos Andes, e na
interação com diferentes fatores erosivos. Em particular, a precipitação desempenha um
relevante função na dinâmica sedimentar. Portanto, este trabalho apresenta a análise da
variabilidade espaço-temporal das precipitações com a descarga de água e a concentração
de sedimentos em suspensão na sub-bacia do Alto Madeira. Mediante a avaliação da fração
fina do sedimento em suspensão na saída dos principais tributários - rios Beni e Mamoré -
, verificou-se que a diminuição da concentração de sedimentos em suspensão, à jusante do
Complexo Hidrelétrico do Madeira (Barragens de Jiraú e Santo Antônio) na estação de
Porto Velho, no Brasil, está parcialmente relacionada com a diminuição de sedimentos, à
montante das barragens no Rio Beni. No entanto, a existência de diferentes hipóteses
relacionadas com dita diminuição, bem com os limitados dados disponíveis no Rio Andino
Madre de Dios e na parte média da sub-bacia, impossibilitou concluir com certeza a
principal razão para a diminuição. Uma das hipóteses, foi a mudança na variabilidade
espaço-temporal da precipitação que pode limitar o sedimento do rio. Por isso,
considerando que a estação de Rurrenabaque representa quase o 60% dos sedimentos em
suspensão na saída do Rio Andino Beni (Vauchel et al. 2017), foram avaliadas as relações
de precipitação, descarga de água e concentração de sedimentos em suspensão. Porém, a
principal causa relacionada à diminuição não foi bem descrita apenas pela avaliação em
Rurrenabaque, mas a avaliação entre a vazão superficial e a base com a concentração de
sedimentos em suspensão mostrou o duplo papel da precipitação na dinâmica dos
sedimentos em suspensão, em primeiro lugar promovendo o desprendimento de materiais
sólidos e sua mobilização para o canal do rio pelo fluxo superficial e, em segundo lugar, através da recarga de águas subterrâneas que promove a diluição da concentração de
sedimentos. A primeira permitiu a estimativa da concentração de sedimentos em suspensão
com base em uma função empírica sazonal de descarga de água que foi comparada com
uma estimativa probabilística (funções de Copula). Como descrito acima, a precipitação
tem um papel chave na dinâmica dos sedimentos em suspensão e, para poder ter um
conjunto de dados validados de precipitação para avaliar as relações entre as variáveis, o
produto CHIRP, versão 2.0, foi estudado de acordo com os principais modos de
variabilidade de precipitação na região andina da sub-baci
A database of freshwater fish species of the Amazon Basin
Get PDFThe Amazon Basin is an unquestionable biodiversity hotspot, containing the highest freshwater biodiversity on earth and facing off a recent increase in anthropogenic threats. The current knowledge on the spatial distribution of the freshwater fish species is greatly deficient in this basin, preventing a comprehensive understanding of this hyper-diverse ecosystem as a whole. Filling this gap was the priority of a transnational collaborative project, i.e. the AmazonFish project - https://www.amazon-fish.com/. Relying on the outputs of this project, we provide the most complete fish species distribution records covering the whole Amazon drainage. The database, including 2,406 validated freshwater native fish species, 232,936 georeferenced records, results from an extensive survey of species distribution including 590 different sources (e.g. published articles, grey literature, online biodiversity databases and scientific collections from museums and universities worldwide) and field expeditions conducted during the project. This database, delivered at both georeferenced localities (21,500 localities) and sub-drainages grains (144 units), represents a highly valuable source of information for further studies on freshwater fish biodiversity, biogeography and conservation
Population dynamics of attalea excelsa (arecaceae) in floodplain forest of the amazonian estuary
No full textSix new species of Tetrapyrgos (Basidiomycota, Agaricales, Marasmiaceae) from the Brazilian Amazon
No full textExperimental forest fragmentation alters Amazonian mixed-species flocks
No full textHabitat fragmentation has been associated with myriad negative effects for forest-dependent birds in the Neotropics. However, the vast majority of negative effects have been inferred from comparisons of pre-existing fragments with separate control sites. Such comparisons confound area loss with isolation and ignore effects of patchy distributions and local habitat heterogeneity. To directly test the effects of fragmentation on Amazonian mixed-species flocks—a complex and diverse species interaction network—we observed birds before and after re-isolation of three 10-ha fragments at the Biological Dynamics of Forest Fragments Project in central Amazonia. Following initial isolation in the 1980s, these fragments have been surrounded by a matrix of developing second growth that was cut again in 2013–2014 (re-isolation). Simultaneously, we also followed three control flocks in primary forest that bordered tall secondary forest. We quantified species richness and attendance, home range size, proportional use of edge and second growth, and space use for fragment and control flocks before and after re-isolation. Following re-isolation, one flock disappeared entirely and half of the obligate flock-followers either vanished or decreased attendance rates. Home ranges of fragment flocks shrunk, and movements were confined by newly created hard edges. These results provide direct experimental evidence that isolation leads to the deterioration and collapse of flocks in forest fragments, affecting both direct metrics and emergent properties of a complex social network. This study also provides retrospective insight into the value of adjacent second growth habitat as immigration corridors for birds in mixed-species flocks. © 2020 Elsevier Lt
