Amazonian waters are classified into three biogeochemical categories by dissolved nutrient content, sediment type, transparency, and acidity—all important predictors of autochthonous and allochthonous primary production (PP): (1) nutrient-poor, low-sediment, high-transparency, humic-stained, acidic blackwaters; (2) nutrient-poor, low-sediment, high-transparency, neutral clearwaters; (3) nutrient-rich, low-transparency, alluvial sediment-laden, neutral whitewaters. The classification, first proposed by Alfred Russel Wallace in 1853, is well supported but its effects on fish are poorly understood. To investigate how Amazonian fish community composition and species richness are influenced by water type, we conducted quantitative year-round sampling of floodplain lake and river-margin habitats at a locality where all three water types co-occur. We sampled 22,398 fish from 310 species. Community composition was influenced more by water type than habitat. Whitewater communities were distinct from those of blackwaters and clearwaters, with community structure correlated strongly to conductivity and turbidity. Mean per-sampling event species richness and biomass were significantly higher in nutrient-rich whitewater floodplain lakes than in oligotrophic blackwater and clearwater river-floodplain systems and light-limited whitewater rivers. Our study provides novel insights into the influences of biogeochemical water type and ecosystem productivity on Earth’s most diverse aquatic vertebrate fauna and highlights the importance of including multiple water types in conservation planning.
The Amazon River basin hosts the most diverse freshwater ichthyofauna in the world, and yet huge areas of the basin remain unexplored. This is the case for the upper tributaries of the rio Negro, especially those draining the Colombian territory. Here we present a list of 224 species derived from the examination of specimens collected in the Mitú region (Vaupés Department, Colombia), the middle basin of the río Vaupés. Of the species identified in our study, 10 species are recorded from Colombia for the first time, and 26 species are newly recorded from the Colombian Amazon. The number of species we present here comprise almost one-third of the known species diversity of the Colombian Amazon and nearly a tenth of the total number of those known across the entirety of the Amazon basin. The most diverse orders were Characiformes (120 species) and Siluriformes (65 species), and the remaining six orders comprised less than 20% of total species. The study area comprised blackwater systems, which are considered to be nutrient-poor environments. We discuss some ecological aspects that might explain how this highly diverse ichthyofauna originates and is maintain in less productive systems. The list presented here adds an important number of new records and complements the information derived from previous studies, carried out thus far with regards to the fish fauna of the Colombian Amazon.
Riverine floodplains are biologically diverse and productive ecosystems. Although tropical floodplains remain relatively conserved and ecologically functional compared to those at higher latitudes, they face accelerated hydropower development, climate change, and deforestation. Alterations to the flood pulse could act synergistically with other drivers of change to promote profound ecological state change at a large spatial scale. State change occurs when an ecosystem reaches a critical threshold or tipping point, which leads to an alternative qualitative state for the ecosystem. Visualizing an alternative state for Amazonian floodplains is not straightforward. Yet, it is critical to recognize that changes to the flood pulse could push tropical floodplain ecosystems over a tipping point with cascading adverse effects on biodiversity and ecosystem services. We characterize the Amazonian flood pulse regime, summarize evidence of flood pulse change, assess potential ecological repercussions, and provide a monitoring framework for tracking flood pulse change and detecting biotic responses.
A new species of Bryconops is described from the rio Maicuru, a tributary of the left margin of the lower Amazon River, Pará, Brazil. Bryconops chernoffi new species, differs from all its congeners by the presence of an elongated dark patch of pigmentation immediately after the posterodorsal margin of the opercle, running vertically from the supracleithrum to the distal margin of the cleithrum (vs. absence of a similar blotch), and by a dark dorsal fin with a narrow hyaline band at middle portion of dorsal-fin rays (vs. dorsal fin hyaline or with few scattered chromatophores). It differs further from all its congeners, except B. colanegra, by the presence of a blurred black stripe at the anal fin base. It differs from B. colanegra by possessing fewer predorsal scales (8–9 vs. 10–11) and in that the third infraorbital contacts the preopercle ventrally (vs. third infraorbital not contacting preopercle ventrally). The new species is assigned to the subgenus Creatochanes by the number of maxillary teeth, and ossification and denticulation of the gill rakers.
The geographic distribution of a catfish of the family Loricariidae, Rineloricaria daraha Rapp Py-Daniel and Fichberg, 2008, which was only known from its type locality within the Rio Daraá, Brazil, is extended here within the Rio Negro basin to Colombia. This new record from Colombian territory is more than 700 km apart, in hydrological distance, from previously recorded locality in the Rio Daraá. Illustrations of diagnostic characters and morphometrics are provided based on Colombian specimens.
Explaining the mechanisms underlying spatial and temporal variation in community composition is a major challenge. Nevertheless, the processes controlling temporal variation at a site (i.e., temporal β-diversity, including its turnover and nestedness components) are less understood than those affecting variation among sites (i.e., spatial β-diversity). Short-term temporal turnover (e.g., throughout an annual cycle) is expected to correlate positively with seasonal environmental variability and landscape connectivity, but also species pool size (γ-diversity). We use the megadiverse Amazonian freshwater ichthyofauna as a model to ask whether seasonality and landscape connectivity drive variation in temporal species turnover among geomorphological habitat types, while taking into account between-habitat variation in γ-diversity. 11,397 fish representing 260 species were collected during a year-long sampling program in an area containing the lowland Amazon’s four major geomorphological habitat types: rivers, floodplains, terra firme streams, and shield streams. River-floodplain systems exhibit strong but predictable seasonality (via a high-amplitude annual flood pulse), high connectivity, and high species richness with many rare species. Terra firme and shield streams exhibit low seasonality, low connectivity, and low species richness with proportionally fewer rare species. Based on these parameters we predicted that river-floodplain systems should have higher temporal turnover than stream systems. Using a null model approach combined with β-deviation calculations, we confirmed that rivers and floodplains do exhibit higher turnover (but not nestedness) than terra firme and shield streams, even when controlling for the potentially confounding effect of higher species richness in river-floodplain systems. All habitats exhibit low temporal nestedness, indicating that short-term changes in community composition result primarily from temporal species turnover. Our results provide a timely reminder that efforts to conserve the Amazon’s threatened aquatic biodiversity should account for the distinct temporal dynamics of habitat types and variation in hydrological seasonality.
Registros de literatura, complementados con la revisión de ejemplares de colección de referencia de peces del Instituto Humboldt - IAvH-P (Colombia), Estación Biológica de Rancho Grande - EBRG y Museo de Ciencias Naturales de Guanare - MCNG (Venezuela), muestran que 109 especies nativas de agua dulce y 14 de origen marino y estuarino habitan la subcuenca el río Catatumbo, constituyéndose en el sistema con mayor diversidad de especies de peces de la cuenca del Lago de Maracaibo. Estas especies pertenecen a 10 órdenes, 39 familias y 91 géneros. Los órdenes con mayor número de familias, géneros y especies fueron Siluriformes con 12 familias, 42 géneros y 60 especies, y Characiformes 11 familias, 24 géneros y 32 especies. Las familias con mayor riqueza fueron Loricariidae (16 géneros y 25 especies), Characidae (13 géneros y 18 especies) y Pimelodidae (6 géneros y 8 especies); presentando las restantes 37 familias entre una y cinco especies. De las 123 especies registradas, 69 fueron capturadas y catalogadas como resultados de los muestreos durante el presente estudio y 11 corresponden a nuevos registros para Colombia. Para el río Catatumbo se registraron 61 especies de las 68 consideradas endémicas para la cuenca del Lago de Maracaibo y se establecieron como especies pesqueras 40, de las cuales seis fueron marino-estuarinas y 34 dulceacuícolas. Se discute las variaciones del número de especies registradas en los diferentes listados y sus implicaciones en la riqueza de especies para la subcuenca del Catatumbo.
Based on a rigorous analysis of fish collections of the Instituto Amazónico de Investigaciones Científicas (Sinchi) and new collections by us, we report new Colombian records and geographical range extensions for freshwater fish species. The new occurrences include representatives of four taxonomic orders, eight families, and 13 genera. Our findings expand the geographic ranges of fish species within the Amazon and Orinoco basins and include species reported from Colombia for the first time. This information is fundamental for completion of species inventories, as well as analyses of freshwater fish diversity patterns at macroecological scales. In addition, our data provide useful information for the formulation of strategies for the conservation, management, and sustainable use of biodiversity.
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