A ictiofauna do interflúvio Purus-Madeira e os fatores estruturantes em múltiplas escalas

The goal of this study was to increase our knowledge about the stream-fish fauna of PurusMadeira Interfluve and evaluate the main ecological gradients that act in the assemblages structuring, incorporating both spatial and temporal scales. In the first chapter we present a checklist of streamfish of Purus-Madeira Interfluve, built up from new expeditions to difficult-to-access drainages and also by incorporating the previously listed records for the region. The final list consisted of 184 species, of which 43 were only collected in our samples and five genera represent new records for the Madeira River basin. The number of species recorded is higher than those usually found in other stream studies in the Amazon and suggests that this region harbor a biodiversity whose structuring factors still need to be better understood. In the second chapter we seek to understand how the taxonomic and functional diversity patterns of stream fish assemblages are influenced by local and landscape variables. Our results indicate that, at large spatial scales, distance to large rivers is more important than distance among sites and local conditions in explaining functional and taxonomic diversity of fish assemblages and more isolated streams tend to have fewer species and less functional diversity. In the third chapter, we analyze the interannual variation in the composition of fish assemblages of 11 intermittent streams of the Purus-Madeira Interfluvie. The composition of the assemblages was quite variable between years, however the streams more connected with the floodplain presented more stable assemblages and shared more species between years, while the most distant assemblages present high species substitution over the analyzed period. Our results provides a clue that these assemblages are structured both by stochastic processes of dispersion and local extinction, and by the recruitment dynamics of the floodplain.O objetivo desta tese foi ampliar o nível de conhecimento sobre a fauna de peixes de riacho do interflúvio Purus-Madeira e compreender quais os principais gradientes ecológicos que atuam na estruturação das assembleias, incorporando tanto escalas espaciais quanto temporais. No primeiro capítulo nós apresentamos uma lista de ocorrência dos peixes de riacho do interflúvio Purus-Madeira, construída a partir de novas expedições às drenagens de difícil acesso e também através da incorporação dos registros previamente listados para a região. A lista final foi composta por 184 espécies, das quais 43 foram apenas coletadas na nossa amostragem e cinco gêneros representam novos registros para a bacia do rio Madeira. O número de espécies registradas é maior do que aqueles usualmente encontrados em outros estudos de riachos na Amazônia e sugere que a região abriga uma biodiversidade cujos fatores estruturantes ainda precisam ser melhor compreendidos. No segundo capítulo nós buscamos compreender como os padrões de diversidade taxonômica e funcional das assembleias de peixes de riacho são influenciados por variáveis locais e da paisagem. Nossos resultados mostram que em amplas escalas geográficas, a distância aos grandes rios é mais importante que a distância por água e que as condições ambientais na determinação de dissimilaridade taxonômica e funcional de assembleias e que riachos mais isolados tendem a ter menos espécies e menos diversidade funcional. No terceiro capítulo, nós analisamos a variação interanual da composição das assembleias de peixes de 11 riachos intermitentes do interflúvio Purus-Madeira. A composição das assembleias foi bastante variável entre anos, entretanto os riachos mais conectados com a planície de inundação apresentaram assembléias mais estáveis e compartilharam mais espécies entre anos, enquanto que as assembléias mais afastadas apresentam alta substituição de espécies ao longo do período analisado. Nossos resultados são um indício de que essas assembléias são estruturadas tanto por processos estocásticos de dispersão e extinção local, quanto pela influência das dinâmicas de recrutamento da planície de inundação

Distance to large rivers affects fish diversity patterns in highly dynamic streams of Central Amazonia

Longitudinal-zonation hypotheses generally predict gradual changes in fish composition from upstream to downstream due to changes in habitat conditions, but largely disregard downstream effects on upstream segments. Floodplains of large rivers represent areas of high connectivity during flood periods and can act as stable refuges in dry seasons, which may attenuate deterministic constraints imposed by local conditions on fish assemblages in surrounding habitats. In this study, we investigated the effects of proximity to large rivers on taxonomic- and functional-diversity patterns of stream-fish assemblages in an extensive region of Central Amazonia. We sampled 31 headwater-stream reaches in nine catchments in the Purus and Madeira Rivers interfluve between December 2014 and March 2015. Ninety seven fish species from seven orders and 19 families were captured. The results indicate that distance to large rivers is more important than distance among sites and local conditions in explaining functional and taxonomic diversity of stream-fish assemblages at large spatial scales. We also found a decrease in taxonomic and functional richness towards headwaters, mainly related to the loss of benthic and sedentary species along the distance gradient. These species may be favored by the proximity to refuge areas and high resource availability near the floodplain. In contrast, upstream assemblages were mainly occupied by small-sized, nektonic species with higher dispersal capacity, highly dependent of allochthonous resources. Downstream effects could be detected for many kilometers upstream in hydrographic catchments and this reinforces the crucial role of connectivity between fluvial habitats in maintenance of stream-fish diversity patterns in the region. © 2019 Stegmann 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

A database of freshwater fish species of the Amazon Basin

The 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

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Environmental filters predict the trait composition of fish communities in reservoir cascades

Dam construction alters flow regimes and can change the composition of aquatic communities. Using data from three Brazilian hydrographic basins, we tested the hypothesis that reservoir cascades act as environmental filters for fish traits. This dataset included information on different environmental variables and fish traits (diet, migration, fecundation, parental care, position in the water column, and body size), and we used multivariate analysis (partial RLQ) to quantify the relationships between environmental variables, species abundance and traits. We found that the abundance of migratory species declined towards downstream reservoirs, which tend to be smaller and less turbid with a shorter water residence time than upstream reservoirs. We also found evidence of an association between reservoir age and the domination of fish communities by small-sized species with parental care, external fecundation, and benthic habits. Our findings suggest that particular fish traits are selected for across reservoir cascades. © 2017, Springer International Publishing AG