Unexpected species diversity in electric eels with a description of the strongest living bioelectricity generator

Is there only one electric eel species? For two and a half centuries since its description by Linnaeus, Electrophorus electricus has captivated humankind by its capacity to generate strong electric discharges. Despite the importance of Electrophorus in multiple fields of science, the possibility of additional species-level diversity in the genus, which could also reveal a hidden variety of substances and bioelectrogenic functions, has hitherto not been explored. Here, based on overwhelming patterns of genetic, morphological, and ecological data, we reject the hypothesis of a single species broadly distributed throughout Greater Amazonia. Our analyses readily identify three major lineages that diverged during the Miocene and Pliocene—two of which warrant recognition as new species. For one of the new species, we recorded a discharge of 860 V, well above 650 V previously cited for Electrophorus, making it the strongest living bioelectricity generator. © 2019, The Author(s)

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

Land use effects on the co-occurrence patterns of streams ichthyofauna in the eastern Amazon

In this manuscript, we aimed to answer: 1) which environmental and spatial processes are determinant for the patterns of co-occurrence of fish in Amazonian streams, and 2) which variables are responsible for the positive and negative associations between species pairs. For this, we sampled 32 Terra-Firme forest streams in a basin affected by different land uses in the eastern Amazon. In each stream, we measured environmental metrics for its physical characterization; estimated the percentage of land cover of the drainage network; and sampled the ichthyofauna. We also analyzed associations (positive or negative) between pairs of species and whether these associations were determined by physical habitat characteristics and the percentage of vegetation cover, spatial dispersal or biotic interactions, using a classical null model approach complemented by spatial tests and of environmental characteristics of the sites occupied by members of each pair of species. Most of the patterns of ichthyofauna co-occurrence occurred at random, composed mainly of rare species, which may be due to the specificity of these species or because the still forested and highly heterogeneous areas of the region may be acting as a mosaic, together with less aggressive land uses such as agriculture, generating these random pairs. Meanwhile, 32 species (41.03%) formed 613 non-random aggregated or segregated pairs (20.41% of the total pairs), composed mainly of species of intermediate frequency and abundance in the region and with different niches and guilds and determined by biotic interactions, environmental filters’ action and/or by limiting species dispersal

How reliable are species identifications in biodiversity big data? Evaluating the records of a neotropical fish family in online repositories

The increase of free and open online biodiversity databases is of paramount importance for current research in ecology and evolution. However, little attention is paid to using updated taxonomy in these “biodiversity big data” repositories and the quality of their taxonomic information is often questioned. Here we assess how reliable is the current use of nomenclatural classification in the distributional information available from two biodiversity information networks: GBIF and the Brazilian SpeciesLink. We use as a study case the records of Auchenipteridae, a Neotropical fish family that has been subject to recent taxonomical reviews. A data filtering procedure was applied to identify and quantify the inaccuracies in the taxonomical status of the records in three steps: assessment of identification accuracy at the family, genus or species level; current validity of species name; and assignation of inaccurate species records to different categories of classification quality. Synonyms, nonexistent combinations, and outdated combinations were reassigned to currently valid species. A total of 9148 records of Auchenipteridae fishes were analyzed, of which 4165 were from GBIF and 4983 from SpeciesLink, deriving from 46 and 31 sources, respectively. After correcting all possible records following the taxonomic data filtering steps, 6988 records (76.4% of the original) were adequate for describing species distributions, while 2160 remained inaccurate. The most inaccurate records at the species level were due to the use of outdated nomenclatures, resulting in non-valid combinations of species and genus, and synonymy. Our results evidence a large taxonomic inconsistency among records, and, most importantly, that taxonomic information obtained from repositories should be used with caution. Many inaccuracy issues may be embedded in the biodiversity databases’ records, which could lead researchers to provide an incomplete or even mistaken perspective of the variations in the natural world.This research was supported by the Coordenacao de Aperfeicoamento de Pessoal de Nıvel Superior - Brasil (CAPES - Finance Code 001) under Grant (TMSF23038.042984/2008-30); CNPq (Conselho Nacional de Desenvolvimento Cientıfico e Tecnologico) under Grant (PDM308694/2015-5; LFAM305017/2016-0; JH314523/2014-6)

Mine tailings storage dams modify upstream headwater fish assemblages

Riverscape connectivity is a critically important component determining the ecological condition of lotic ecosystems. We evaluated changes in fish assemblages caused by the loss of connectivity by mine tailings storage dams (TSDs), hypothesizing that headwater fish assemblages are restructured by TSDs located downstream, even though the upstream habitats are not altered. We used standard methods to collect fish in 24 first to third order sites, with half draining to TSDs (dammed) and the other half free from this impact (undammed). To identify differences between treatments, we used PERMANOVA to test both environmental variables and ichthyofauna composition (Bray-Curtis similarity index) and evaluated the biological metrics that most influenced assemblage composition change. As expected, we observed no difference between treatments for environmental variables, but we did observe differences in fish assemblage composition. We also observed five metrics with lower values in dammed streams (richness and abundance of intolerant species, siluriform richness, and abundance of Pareiorhaphis cf. proskynita and Trichomycterus brasiliensis) and two metrics with higher values in dammed streams (perciform richness and abundance of Oligosarcus argenteus). We believe these changes resulted from of stream fragmentation by TSDs, in addition to source-sink mechanisms and conclude that mine TSDs located downstream change headwater fish assemblages, an impact often neglected in biomonitoring and bioassessment studies

Thresholds of freshwater biodiversity in response to riparian vegetation loss in the Neotropical region

Protecting riparian vegetation around streams is vital in reducing the detrimental effects of environmental change on freshwater ecosystems and in maintaining aquatic biodiversity. Thus, identifying ecological thresholds is useful for defining regulatory limits and for guiding the management of riparian zones towards the conservation of freshwater biota. Using nationwide data on fish and invertebrates occurring in small Brazilian streams, we estimated thresholds of native vegetation loss in which there are abrupt changes in the occurrence and abundance of freshwater bioindicators and tested whether there are congruent responses among different biomes, biological groups and riparian buffer sizes. Mean thresholds of native vegetation cover loss varied widely among biomes, buffer sizes and biological groups: ranging from 0.5% to 77.4% for fish, from 2.9% to 37.0% for aquatic invertebrates and from 3.8% to 43.2% for a subset of aquatic invertebrates. Confidence intervals for thresholds were wide, but the minimum values of these intervals were lower for the smaller riparian buffers (50 and 100 m) than larger ones (200 and 500 m), indicating that land use should be kept away from the streams. Also, thresholds occurred at a lower percentage of riparian vegetation loss in the smaller buffers, and were critically lower for invertebrates: reducing only 6.5% of native vegetation cover within a 50-m riparian buffer is enough to cross thresholds for invertebrates. Synthesis and applications. The high variability in biodiversity responses to loss of native riparian vegetation suggests caution in the use of a single riparian width for conservation actions or policy definitions nationwide. The most sensitive bioindicators can be used as early warning signals of abrupt changes in freshwater biodiversity. In practice, maintaining at least 50-m wide riparian reserves on each side of streams would be more effective to protect freshwater biodiversity in Brazil. However, incentives and conservation strategies to protect even wider riparian reserves (~100 m) and also taking into consideration the regional context will promote a greater benefit. This information should be used to set conservation goals and to create complementary mechanisms and policies to protect wider riparian reserves than those currently required by the federal law. © 2020 British Ecological Societ