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)

Evolution of South American cichlid fishes with an emphasis on the genus Apistogramma

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Discus fishes: Mitochondrial DNA evidence for a phylogeographic barrier in the Amazonian genus Symphysodon (Teleostei: Cichlidae)

Genetic relationships and variation in meristic counts, body shape and colour were examined in a large sample of Symphysodon collected from several locations in floodplain habitats along the length of the Amazon River. Surprisingly, mitochondrial DNA indicates no difference between the two historically described species, Symphysodon discus and Symphysodon aequifasciatus, but shows that non-clinal variation exists with a distinct lineage found in the western Amazon. This lineage is consistent with a colour form that is distinct from other Symphysodon lineages. This form has a parapatric distribution and is recognized as a distinct species, Symphysodon tarzoo. Adaptation to floodwater habitats supports genetic cohesion across a large range preventing fine scale regional diversification of the genus. Possible explanations for the unusual set of distributions for genetic and colour characters relate to the history of the Amazon basin and the probable division of lowland species when submerged geologic arches influence surface topology. © 2006 The Fisheries Society of the British Isles

Holistic multi-method survey to enhance Madagascar's freshwater fish conservation

<p>Freshwater ecosystems are crucial for global biodiversity, supporting plant and animal species and providing essential resources. However, these ecosystems, particularly in island environments such as Madagascar, are under significant threat. Our study focuses on the Amboaboa River basin, home to the rare and endemic fish species <i>Rheocles derhami</i>, last recorded in 2013. To assess the status of this and other threatened fish species including <i>Ptychochromis insolitus</i> and <i>Paretroplus gymnopreopercularis</i>, and to understand freshwater fish population dynamics in this biodiversity hotspot, we conducted a comprehensive survey using both environmental DNA (eDNA) and traditional fishing methods. Our findings reveal updated records of <i>Rheocles derhami</i> and an expanded species list within these freshwater environments. We also explore the implications of combining these two monitoring approaches and investigate the trade-offs associated with multi-primer assessments in eDNA analysis, focusing on three different primers targeting the 12S mitochondrial gene: MiFish, Tele02, and Riaz. Additionally, we provide 12S reference barcodes for 10 species across 9 genera of fishes from the region to increase the coverage of the public reference databases. Overall, our study enlightens the current state of freshwater biodiversity in Amboaboa River basin and underscores the value of employing multiple methods for effective conservation strategies.</p&gt

An inverse latitudinal gradient in speciation rate for marine fishes

Far more species of organisms are found in the tropics than in temperate and polar regions, but the evolutionary and ecological causes of this pattern remain controversial1,2. Tropical marine fish communities are much more diverse than cold-water fish communities found at higher latitudes3,4, and several explanations for this latitudinal diversity gradient propose that warm reef environments serve as evolutionary ‘hotspots’ for species formation5,6,7,8. Here we test the relationship between latitude, species richness and speciation rate across marine fishes. We assembled a time-calibrated phylogeny of all ray-finned fishes (31,526 tips, of which 11,638 had genetic data) and used this framework to describe the spatial dynamics of speciation in the marine realm. We show that the fastest rates of speciation occur in species-poor regions outside the tropics, and that high-latitude fish lineages form new species at much faster rates than their tropical counterparts. High rates of speciation occur in geographical regions that are characterized by low surface temperatures and high endemism. Our results reject a broad class of mechanisms under which the tropics serve as an evolutionary cradle for marine fish diversity and raise new questions about why the coldest oceans on Earth are present-day hotspots of species formation