Turbidity plays an important role in aquatic predator–prey interactions. Increases in turbidity are expected to reduce prey capture rates, especially for visually oriented predators. However, there ...is also evidence indicating that turbidity may have little or no effect on predation rates.
Here, we conducted a systematic review and meta‐analysis of the relationship between turbidity and capture rate. We explored possible sources of heterogeneity in the effect sizes (capture strategy, predator's body size, relative eye size and turbidity range in the experiments) while controlling for the dependence among effects sizes and phylogenetic relationships among predator species.
We found a consistent negative effect of turbidity on prey capture and that turbidity range (manipulated in the experiments) was the main factor accounting for between‐study variation in effect sizes. Also, capture rates of both visually and non‐visually oriented predators decreased with an increase in turbidity. In addition, for visually oriented fish predators, the relative eye size did not influence the effect sizes.
Despite the paucity of studies for some groups of aquatic predators (mainly in tropical regions), we provide corroborative evidence that turbidity is a critical environmental factor controlling predator–prey interactions. This result is especially relevant considering that changes in turbidity is a human‐induced pervasive environmental alteration resulted from, among other mechanisms, runoff after deforestation, eutrophication or oligotrophication in reservoir cascades, which imply changes in predator–prey interactions.
This meta‐analysis shows that turbidity reduces prey capture by aquatic predators with different predation strategies. Only the range in turbidity explains differences among experiments. These results highlight that turbidity drives predator‐prey dynamics in aquatic environments and draws attention to current and projected changes in water transparency caused by anthropogenic activities.
This work aimed to describe Cambeva cauim, sp. nov., endemic to the Rio Iguaçu basin, Brazil and redescribe Cambeva stawiarski using external and internal morphological data through the revision of ...specimens deposited in fish collections, including the type material. In this process, we have also added comments on the possible type locality of C. stawiarski. C. cauim, sp. nov. and C. stawiarski are mainly diagnosed by the anatomy and number of procurrent caudal‐fin rays in addition to colouration and several meristic and morphometric characters. Both species are compared with other possibly related species and their synapomorphic characters are discussed. C. cauim, sp. nov. and C. stawiarski along with eight other congeners are endemic to the Rio Iguaçu basin, a high impacted freshwater region which could be considered as a biodiversity hotspot to the genus.
A new species of Cambeva endemic to the Rio Ivaí basin, Upper Paraná basin, is described combining morphological and molecular data. This new species is distinguished from all congeners by characters ...related to the number of pectoral‐fin rays, to the colour pattern of the dorsal and lateral surface of the body, to the presence of diffuse blotches in the ventral surface of body, to the presence of a pelvic‐fin and pelvic girdle, to the number of odontodes in the inter‐opercular and opercular patches, to the number of dorsal and ventral procurrent rays. In addition, the analysis of mitochondrial DNA sequences identified a satisfactory genetic distance between this new species and its congeners. The new species from the Rio Ivaí reinforces its characteristics as an area of endemism for fishes in the Upper Rio Paraná basin.
Distributional, phylogenetic, molecular, and paleontological data may be integrated to discover biogeographic patterns exhibited by the organisms. Cladistic biogeography uses information on the ...phylogenetic relationships between taxa and their geographic distribution to infer a sequence of area fragmentation. Brooks Parsimony Analysis (BPA) was performed based on the phylogenetic proposals for Cnesterodontini to hypothesize on the historical relationships among nine areas previously recognized by endemism of freshwater fish from South America. Additionally, we investigated the conservation scenario for cnesterodontines based on biogeographic, phylogenetic, and extinction criteria to establish a priority ranking for the analyzed areas. We found that the area relationships for Cnesterodontini are strongly linked to the historical patterns of evolution of the hydrographic basins, revealing well-defined scenarios of the formation of hydrological barriers between coastal river basins (i.e., Atlantic Slope) and mainly drainages running into the La Plata River system (i.e., Inland Slope). Dispersal events through headwater capture and sea-level changes explain the congruences evidenced among other fish lineages that exhibit similar diversification patterns in the Central Brazil drainages and in drainages on the Atlantic coast of South America. The ranking of priority areas for conservation established for Cnesterodontini indicates that greater attention should be directed to the regions located in the Central Coastal and Upper Parana areas, mainly in the Atlantic Forest, which represents one of the most threatened biodiversity hotspots on the planet with serious threats to freshwater biodiversity.
Cambeva piraquara, sp. nov., a restricted-range and rare species last collected from over 20 years ago, is described from the Rio Piraquara, upper Rio Iguacu basin, Rio Parana (La Plata) system. The ...new species is distinguished from all congeners by having two conspicuous dark-brown longitudinal stripes on the inner skin layer of body over a plain yellowish background: a conspicuous wide and well-defined dark-brown longitudinal mid-lateral stripe extending from the opercular patch of odontodes to the first third of caudal-fin rays and a dorso-sagittal stripe comprising large and coalescent rounded blotches extending from occipital to the dorsal-fin base. We provide an illustrated osteological description and assess the conservation status of the new species, which faces several environmental impacts in the upper Rio Iguacu basin.
Landscape dynamics are widely thought to govern the tempo and mode of continental radiations, yet the effects of river network rearrangements on dispersal and lineage diversification remain poorly ...understood. We integrated an unprecedented occurrence dataset of 4,967 species with a newly compiled, time-calibrated phylogeny of South American freshwater fishes-the most species-rich continental vertebrate fauna on Earth-to track the evolutionary processes associated with hydrogeographic events over 100 Ma. Net lineage diversification was heterogeneous through time, across space, and among clades. Five abrupt shifts in net diversification rates occurred during the Paleogene and Miocene (between 30 and 7 Ma) in association with major landscape evolution events. Net diversification accelerated from the Miocene to the Recent (c. 20 to 0 Ma), with Western Amazonia having the highest rates of in situ diversification, which led to it being an important source of species dispersing to other regions. All regional biotic interchanges were associated with documented hydrogeographic events and the formation of biogeographic corridors, including the Early Miocene (c. 23 to 16 Ma) uplift of the Serra do Mar and Serra da Mantiqueira and the Late Miocene (c. 10 Ma) uplift of the Northern Andes and associated formation of the modern transcontinental Amazon River. The combination of high diversification rates and extensive biotic interchange associated with Western Amazonia yielded its extraordinary contemporary richness and phylogenetic endemism. Our results support the hypothesis that landscape dynamics, which shaped the history of drainage basin connections, strongly affected the assembly and diversification of basin-wide fish faunas.
Abstract Characidium xavante was described from two tributaries of the Culuene River drainage, in the upper Xingu River basin. New samplings recorded the species for streams from the Kaaiapó River ...drainage (Teles Pires River drainage, upper Tapajós River basin) with additional specimens also recorded in the Xingu River basin, Paranatinga municipality, Mato Grosso State, Brazil. The new records represent an extension of the geographical distribution of the species, that from now on fits in a pattern of distribution known to be shared with other ca. 20 species of fishes. We suggest that Characidium xavante could be classified as Least Concern (LC), according to the International Union for Conservation of Nature Standards and Petitions Committee (IUCN).
Phylogenetic comparative studies suggest that the direction of deviation from bilateral symmetry (sidedness) might evolve through genetic assimilation; however, the changes in sidedness inheritance ...remain largely unknown. We investigated the evolution of genital asymmetry in fish of the family Anablepidae, in which males' intromittent organ (the gonopodium, a modified anal fin) bends asymmetrically to the left or the right. In most species, males show a 1 : 1 ratio of left-to-right-sided gonopodia. However, we found that in three species left-sided males are significantly more abundant than right-sided ones. We mapped sidedness onto a new molecular phylogeny, finding that this left-sided bias likely evolved independently three times. Our breeding experiment in a species with an excess of left-sided males showed that sires produced more left-sided offspring independently of their own sidedness. We propose that sidedness might be inherited as a threshold trait, with different thresholds across species. This resolves the apparent paradox that, while there is evidence for the evolution of sidedness, commonly there is a lack of support for its heritability and no response to artificial selection. Focusing on the heritability of the left : right ratio of offspring, rather than on individual sidedness, is key for understanding how the direction of asymmetry becomes genetically assimilated.
A new miniature species of Characidium is described from the upper Rio Paraguay basin, Brazil. The new species can be diagnosed from all congeners by the presence of a dark‐brown humeral blotch, ...vertically elongated (spanning 5 to 7 horizontal scale rows), with the shape of an upside‐down acute triangle. Additionally, it can be diagnosed by a short lateral line (6 to 8 perforated scales), the absence of a conspicuous peduncular blotch, a lower number of principal caudal‐fin rays (14–16) and by absence of the adipose fin. The new species is the smallest species of the genus; the largest specimen was 19.3 mm standard length.
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