Patterns of population differentiation in annual killifishes from the Paraná–Uruguay–La Plata Basin: the role of vicariance and dispersal

Aim To elucidate the role of vicariance versus dispersal at the microevolutionary scale in annual killifish populations belonging to the Austrolebias bellottii species complex (Rivulidae). Within this complex, A. bellottii and A. apaii have low vagility and occur widely within the study area, making them excellent models for testing biogeographic hypotheses of differentiation. Location South America, in the Paraná–Uruguay–La Plata river basin. Methods Molecular data and morphometric analyses were used to reconstruct the phylogeographic history and morphological variation of 24 populations of two taxa of the A. bellottii species complex. Phylogenetic analyses using maximum likelihood (ML) and Bayesian inference (BI) model‐based methods, estimates of clade divergence times implemented in beast , non‐metric multidimensional scaling, analysis of molecular variance results, and morphological analyses elucidated the role of vicariance versus dispersal hypotheses in population differentiation in the aforementioned river basin. Results In the A. bellottii species complex from the Paraná–Uruguay–La Plata river basin, past allopatric fragmentation from vicariance events seems to be the most plausible scenario for diversification since the Late Miocene and more recently since the Plio‐Pleistocene. The Plio‐Pleistocene vicariance produced the differentiation of three major clades in A. bellottii populations. One clade from the eastern Uruguay River drainage was separated from another in western Uruguay and the Paraná–La Plata River drainages. A later vicariance event split populations to the south (lower Paraná–La Plata Basin) and north (middle Paraná) of the western Paraná River drainage. However, our results do not exclude the possibility of dispersal events among A. bellottii populations from both the Uruguay and Paraná river drainages, which could occur in these river basins during hypothesized connectivity cycles of the Late Pliocene and Pleistocene. Main conclusions Past allopatric fragmentation caused by different vicariance events seems to be the main driver of diversification in the A. bellottii species complex since the Plio‐Pleistocene. However, the current molecular data suggest that populations from both drainages of the Paraná–Uruguay rivers may have experienced cycles of connectivity during the Pleistocene, perhaps including multiple vicariance or dispersal events from populations located in the western lower Uruguay River drainage, which encompassed climatic and geological changes in the Paraná–Uruguay–La Plata Basin.     

Sympatry between <Emphasis Type="Italic">Alouatta caraya</Emphasis> and <Emphasis Type="Italic">Alouatta clamitans</Emphasis> and the rediscovery of free-ranging potential hybrids in Southern Brazil

Records of sympatry between Alouatta caraya and A. clamitans are rare despite their extensive range overlap. An example of their current sympatry and the rediscovery of free-ranging potential hybrids of A. caraya and A. clamitans in the forests of the Upper Paraná River, Southern Brazil, are reported in this paper. Eight groups were observed in the study area: five monospecific groups of A. caraya, two of A. clamitans, and a group containing two adult males and two adult females of A. caraya and a sub-adult male and two adult females identified as Alouatta sp. The color of the last three individuals was a mosaic between the two species; this is consistent with previously described variations in museum specimens collected in the Paraná River in the 1940s that had been identified as potential hybrids. The results from this study emphasize the need for scientific studies in the region of the Ilha Grande National Park, one of the few regions in the Paraná River that currently harbors both howler species. Contribution number 1637 of the Departamento de Zoologia, Universidade Federal do Paraná, Caixa Postal 19020, 81531-980, Curitiba, Paraná, Brasil.     

Genetic structure and evidence of anthropogenic effects on wild populations of two Neotropical catfishes: baselines for conservation

Genetic diversity and structure of Pseudoplatystoma corruscans and P. reticulatum, large migratory South America catfishes, where overfishing and the construction of numerous dams in their feeding and reproducing areas are affecting their migratory processes negatively, were studied using microsatellites in samples from Paraguay (that comprises the Pantanal biome), and the upper and lower Paraná Basins. Genetic diversity was in accordance to that observed for other large migratory fishes, but the most geographically isolated populations of P. reticulatum and those P. corruscans subject to anthropogenic effects (stocking and dams) showed lower genetic diversity and evidences of bottlenecks compatible with low effective population size. Pseudoplatystoma reticulatum presented subtle genetic differentiation within the Paraguay area, especially between the edges of its distribution. Pseudoplatystoma corruscans, in this same area, presented a quite homogeneous but significant genetic break between the Paraguay and upper Paraná populations, apparently resulting from natural and historical isolation between the basins until recently. These data demonstrates that, although these Pseudoplatystoma spp. are abundant in the Pantanal area, anthropogenic events are leading to negative effects on their populations, particularly in the upper Paraná Basin. Genetic differentiation observed along each species distribution demands conservation actions to preserve each population's biodiversity. These results represent important genetic information using new microsatellite markers and the first genetic study of P. reticulatum covering this area of its native distribution. Data may also contribute to a better understanding of species migration patterns and to be used as a baseline for proper management.     

Has the bumblebee <Emphasis Type="Italic">Bombus bellicosus</Emphasis> gone extinct in the northern portion of its distribution range in Brazil?

Evidence for the extinction of the bumblebee Bombus bellicosus in Paraná state, in Brazil, is presented. The species is found in areas covered with open grass fields and shrub vegetation, originally ranging from northwestern Argentina to Paraná, where it reached its northeastern limit. Until the early 1980s, B. bellicosus was relatively abundant in Paraná, when the last known specimens were collected. In recent surveys conducted from 2002 to 2005, no specimens were recovered at sites in which the species was previously known to occur. Possible causes for local extinction of this species are discussed, including habitat conversion, pollution and climate change.     

Taxonomic revision of Hypostomus albopunctatus (Siluriformes: Loricariidae) reveals a new piece of the Hypostomus jigsaw in the upper Rio Paraná basin

Hypostomus albopunctatus was described from the Rio Piracicaba, a tributary of the Rio Tietê, upper Rio Paraná basin. Nevertheless, specimens attributed to this species are commonly found throughout other river systems in the upper Rio Paraná basin and present varying degrees of morphological variation. A taxonomic review of H. albopunctatus based on large series of specimens from many localities throughout the upper Rio Paraná basin was carried out. Results support H. lexi, H. niger and H. scaphyceps as junior synonyms. Hypostomus albopunctatus differs from all congeners except H. heraldoi by having pectoral-fin spine equal to or shorter than pelvic-fin spine (v. longer); it differs from H. heraldoi by having white or light yellow spots on the body and fins (v. dark brown or black spots). Despite conspicuous variation related to the shape and size of the spots and snout morphology, both spot and snout patterns overlapped among the examined populations, thus this variation was inferred to be intraspecific within a widely distributed H. albopunctatus.     

Morphological and genetic divergence of a small stream fish species along a watershed

Piabina argentea is a species of Characidae family that is widely distributed in the hydrographic basins of the São Francisco and Paraná Rivers and in some Atlantic coastal drainages of South America. The genus contains only one other species, which is restricted to the Tietê River headwaters (the Upper Paraná River Basin) and is considered monophyletic within the Stevardiinae subfamily. Despite the apparent morphological conservation of at least six well-structured clades, great genetic distance revealed by DNA barcoding has already been reported. In an attempt to evaluate the effect of the watershed of the two river basins in the Arc of Upper Paranaíba region (Upper Paraná and São Francisco River basins), we analyzed the populations from both basins using mitochondrial DNA sequences and morphometry and constructed a distribution scenario for the species in both basins.     

Yellow-eyed piranhas produce louder sounds than red-eyed piranhas in an invasive population of Serrasalmus marginatus

Serrasalmus marginatus is a piranha species native from the lower Paraná River basin and has been invasive in the upper Paraná River basin since the 1980s. In piranhas, sounds of different species have different features. The aim of this study was to investigate if the sounds produced by this species could be used to distinguish two morphotypes: red- and yellow-eyed S. marginatus from the Araguari River (upper Paraná River basin). All the temporal and frequency features of the sounds were equivalent in both groups of eye colour; it corresponds to the species-specific signature described for S. marginatus. Nonetheless, the amplitude features were all statistically different between red- and yellow-eyed piranhas. Yellow-eyed specimens produced louder sounds. In different fish species, colour change in eyes can be due to the absence or the presence of a dominant allele. It can also be involved in social rank or during reproduction. Different hormones and neuropeptides can modulate vocal features. It is hypothesized that a mutation or different hormonal concentrations could explain both sound amplitude and eye colour playing a role in animal communication in S. marginatus.     

Trophic ecology and metabolism of two species of nonnative freshwater stingray (Chondrichthyes: Potamotrygonidae)

The stingrays Potamotrygon amandae and Potamotrygon falkneri are nonnative species established in the Upper Paraná basin. Although they are widely distributed, few studies on their diets or respective metabolic responses exist. Therefore, the aim was to evaluate the dietary composition, trophic niche breadth and lipid/protein concentrations in muscle and hepatic tissues of these two species, as well as the interrelationships between them. The individuals were collected in two areas on the Upper Paraná River. The stomachs and samples of muscle and liver tissues were taken for analysis. A broad dietary spectrum was observed for both species, along with differences in dietary composition, with a higher consumption of detritus by P. amandae and Baetidae by P. falkneri. No differences were observed in the trophic niche breadth. Regarding the metabolic variables, differences were only found in the hepatic protein, with a higher content observed in P. falkneri. A significant positive correlation was observed between items of animal origin and detritus with muscle protein for this species. This shows that such feeding habits, which are characteristic of a generalist, influenced the metabolism of the species and possibly contributed to the successful adjustment of the species to new habitats in the Upper Paraná River.

     

A phylogeographical perspective on the ex situ conservation of Aylacostoma (Thiaridae,Gastropoda) from the High Paraná River (Argentina–Paraguay)

Aylacostoma Spix, 1827, contains species that are the subject of focused conservation efforts under the auspices of the ‘Aylacostoma Project’, the only ex situ conservation programme for freshwater gastropods in South America. Two species from the High Paraná River (Argentina–Paraguay) are included in this programme (Aylacostoma chloroticum Hylton Scott, 1954 and Aylacostoma brunneum Vogler & Peso, 2014), as their habitats have disappeared as a consequence of the filling of the Yacyretá Reservoir in the 1990s. At present, A. chloroticum is restricted to only one known wild population in a small and fragile habitat, and wild populations of A. brunneum are presumed to have gone extinct. We used partial sequences of the cytochrome oxidase subunit I gene to provide the first phylogeographical perspective on these species from a limited dataset containing representatives of several wild populations that are successfully being bred in captivity. We found low genetic diversity and two haplotypes in A. chloroticum, and absence of variation with one haplotype in A. brunneum. The reservoir's entry zone was identified to be of great interest for conservation, and is where we suggest re‐introductions and translocations should be targeted, to preserve the future evolutionary potential of the extant diversity. © 2015 The Linnean Society of London     

New species of glass knifefish genus Eigenmannia (Gymnotiformes: Sternopygidae) with comments on the morphology and function of the enlarged cephalic lateral-line canals of Sternopygidae

A new species of Eigenmannia is described from the Rio Paraná (the Grande, Paranapanema and Tietê basins). This new species is distinguished from all congeners by colouration pattern, position of the mouth, relative depth of posterodorsal expansion on infraorbitals 1 + 2, number of teeth, osteological features, number of rows of scales above lateral line (LL) and morphometric data. Comments on the widened cephalic lateral-line canals of Sternopygidae and a dichotomous key to the species of Eigenmannia from the Rio Paraná Basin are provided.     

Transcontinental dispersal,ecological opportunity and origins of an adaptive radiation in the Neotropical catfish genus Hypostomus (Siluriformes: Loricariidae)

Ecological opportunity is often proposed as a driver of accelerated diversification, but evidence has been largely derived from either contemporary island radiations or the fossil record. Here, we investigate the potential influence of ecological opportunity on a transcontinental radiation of South American freshwater fishes. We generate a species‐dense, time‐calibrated molecular phylogeny for the suckermouth armored catfish subfamily Hypostominae, with a focus on the species‐rich and geographically widespread genus Hypostomus. We use the resulting chronogram to estimate ancestral geographical ranges, infer historical rates of cladogenesis and diversification in habitat and body size and shape, and test the hypothesis that invasions of previously unoccupied river drainages accelerated evolution and contributed to adaptive radiation. Both the subfamily Hypostominae and the included genus Hypostomus originated in the Amazon/Orinoco ecoregion. Hypostomus subsequently dispersed throughout tropical South America east of the Andes Mountains. Consequent to invasion of the peripheral, low‐diversity Paraná River basin in southeastern Brazil approximately 12.5 Mya, Paraná lineages of Hypostomus, experienced increased rates of cladogenesis and ecological and morphological diversification. Contemporary lineages of Paraná Hypostomus are less species rich but more phenotypically diverse than their congeners elsewhere. Accelerated speciation and morphological diversification rates within Paraná basin Hypostomus are consistent with adaptive radiation. The geographical remoteness of the Paraná River basin, its recent history of marine incursion, and its continuing exclusion of many species that are widespread in other tropical South American rivers suggest that ecological opportunity played an important role in facilitating the observed accelerations in diversification.     

Testing hypotheses on the origin and dispersion of <Emphasis Type="Italic">Limnoperna fortunei</Emphasis> (Bivalvia,Mytilidae) in the Iguassu River (Paraná, Brazil): molecular markers in larvae and adults

The invasive bivalve Limnoperna fortunei (Dunker 1857) was introduced in South America in 1991, with the first occurrence in Brazil in 1998. In the Iguassu River, the species was recorded in 2001; however, it is unknown how it was introduced and spread. Adults and larvae were sampled in Iguassu and Paraná Rivers, and the genetic profiles were compared. The species was absent in the upper reaches and only larvae were found, in low densities, in intermediary reaches. The L. fortunei populations from the lower Iguassu River presented no genetic differentiation among themselves, suggesting strong connectivity, and were significantly different from the Paraná River populations, most likely because of Iguassu Falls. Furthermore, the results suggest that the Paraná River represents the source of propagules to the Iguassu River. Generally, no significant differences were observed between the genetic structure inferred from adults and larvae. Only the population from the Iguassu National Park, a lotic environment, differed from the remaining subpopulations. The characterization of genetic profile using larval stages of L. fortunei populations was satisfactory, and represents an important protocol for studying the population genetics of aquatic species with planktonic larval stages.     

Acoustic homogeneity in the piranha Serrasalmus maculatus

Different studies suggest some social calls could be used in fish identification if their specificity is unambiguously assessed. Sounds of different populations of piranhas Serrasalmus maculatus Kner, 1858 were recorded to determine their homogeneity between rivers inside a single basin (Araguari and Grande River, upper Paraná River basin) and between separated basins (Amazon and Paraná basins). All fish from the different populations produced sounds with similar acoustic features. Consequently, the populations were not discernible based on individual sound characteristics. This high homogeneity between sounds from different populations indicates their usefulness for conservation projects using passive acoustic monitoring in piranhas. Moreover, it supports the use of acoustic features as complementary key characteristics in taxonomic studies.     

Differentiated ZZ/ZW sex chromosomes in Apareiodon ibitiensis (Teleostei,Parodontidae): cytotaxonomy and biogeography

Conventional and molecular chromosomal analyses were carried out on three populations of Apareiodon ibitiensis sampled from the hydrographic basins of the São Francisco River and Upper Paraná River (Brazil). The results reveal a conserved diploid number (2n = 54 chromosomes), a karyotype formula consisting of 50 m‐sm + 4st and a ZZ/ZW sex chromosome system that has not been previously identified for the species. C‐banding analysis with propidium iodide staining revealed centromeric and terminal bands located in the chromosomes of the specimens from the three populations and allowed the identification of heteromorphism of heterochromatin regions in the Z and W chromosomes. The number of 18S sites located through fluorescent in situ hybridization (FISH) varied between the populations of the São Francisco and Upper Paraná Rivers. The location of 5S rDNA sites proved comparable in one pair of metacentric chromosomes. Thus, the present study proposes a ZZ/ZW sex chromosome system for A. ibitiensis among the Parodontidae, and a hypothesis is presented regarding possible W chromosome differentiation stages in this species through DNA accumulation, showing geographical variations for this characteristic, possibly as a consequence of geographical reproductive isolation.     

Homogenization of freshwater fish faunas after the elimination of a natural barrier by a dam in Neotropics

Aim We quantify biotic homogenization of fish fauna caused by the elimination of a natural barrier between two freshwater ecoregions. We also evaluated fish introductions by different mechanisms such as aquaculture, angling and the aquarium trade in the homogenization of fish assemblages. The relative importance of native extinctions in the homogenization process was assessed by simulating the exclusion of threatened species in the data set. Location Paraná River, south‐eastern South America. Methods A fish species list of the Parana River Basin was organized in a subset of species distributions, according to pre‐ and post‐introductions caused by the elimination of the natural barrier and by other mechanisms. Biotic homogenization was verified by the use of Jaccard’s and Bray–Curtis’s coefficients, Whittaker’s beta diversity index, non‐metric multidimensional scaling analysis (NMDS) and nonparametric tests. Results For all subsets of species distributions, we observed an increase in the number of non‐native species in common related to the introductions. Between 40 and 52% of the species currently present in the Upper Paraná Basin dispersed upstream from the Lower Paraná after the construction of Itaipu Dam, including at least 1 class, 2 orders, 4 families and 16 genera of fish. Jaccard’s coefficient between the Upper and Lower Parana River increased by 6–7.5% only considering the Itaipu Dam influence and 10.5% considering all mechanisms of fish introductions. More than 50% of the increase in similarity was caused by the elimination of the barrier. Our results indicated functional homogenization related to large‐bodied Siluriformes (catfish). Main conclusions Itaipu Lake flooded a natural barrier and allowed hydrologic connectivity between the Upper and Lower Paraná River, and many fishes of the lower part of the river were able to colonize the upper stretches. The homogenization of the two assemblages between these adjacent aquatic regions was an unpredicted result of hydropower implementation. Introductions by dam can also shift longitudinal and latitudinal body size patterns (i.e. Bergmann's rule).     

First observations on longitudinal succession of Zooplankton in the main course of the Paraná River between Santa Fe and Buenos Aires Harbour

The material was been collected in 1972 during a field trip performed by the research vessel of the National Institute of Limnology, Argentina, along the main course of the Paraná River from the Santa Fe harbor down to the Río de la Plata. Sixty sampling stations were covered. In the lower course of the river sampling was carried out in the Paraná Guazú and the Paraná Bravo branches down to its confluence with the Uruguay River, and the Paraná de las Palmas and the Rio de la Plata down to the Buenos Aires harbor. Water samples for chemical analysis were collected and some physical parameters were measured.

Due to the characteristics of the part of the river under consideration, we have divided it into four sectors.

Sixty six species were seen. The rotifers were always the most important. Trichocerca rattus was the predominant species.

The Zooplankton density and specific diversity showing differences between those from industrialized areas and not industrialized ones.     

Isolation and characterization of polymorphic microsatellites in the threatened catfish Jaú, Zungaro jahu (Siluriformes, Pimelodidae)

This paper describes eight polymorphic microsatellite loci of the large migratory catfish Jaú, Zungaro jahu, a threatened species in the Paraguay—Paraná River Basin, which includes the Brazilian wetland Pantanal system. The number of detected alleles varied from 3 to 10, while observed and expected heterozygosity values ranged from 0.3182 to 0.8333 and 0.3298 to 0.8652, respectively. Cross-amplification on five related species was successfully evaluated. These isolated markers demonstrated to be very useful for population studies of this fish and related species, consisting in important tools for evaluations related to the management and conservation of the native populations.     

Cytogenetic studies on Apareiodon affinis (Pisces, Characiformes) from Paraná river basin: sex chromosomes and polymorphism

Comparative cytogenetic studies were carried out on Apareiodon affinis from an important hydrographic system at South America, the Paraná river basin. Two distant regions were chosen, which were separated by Guaíra Falls (formerly Sete Quedas); the region in the upper part of the hydrographic basin is called Upper Paraná (Brazil), whereas and the other in the lower part is called Lower Paraná (Argentina). Individuals from Upper Paraná have diploid numbers of 2n = 54 (NF = 108) for males and 2n = 55 (NF = 110) for females, showing female heterogamety with a ZZ/ZW₁W₂ multiple sex chromosomes system that is endemic for the region. In different localities at Lower Paraná, the specimens presented diploid number of 2n = 54 for both sexes, without any sex chromosomes heteromorphism. However, they have an accentuated polymorphism characterized by variation in number of acrocentric chromosomes, constituting something new for family Parodontidae. The most likely hypothesis to explain the origin of such polymorphism is based on successive pericentric inversions giving rise to acrocentric chromosomes. Thus, it was possible to detect 10 cytotypes along the Lower Paraná basin. Such chromosomal variations possibly are the consequence of an adaptative process. Our data probably indicate the occurrence of distinct species in each region that share the same denomination. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Temporal Asynchrony of Planktonic Cladocerans Population at Different Environments of the Upper Paraná River Floodplain

The aim of this study was to investigate the existence of synchronic fluctuation patterns in cladoceran populations of the Upper Paraná River floodplain. The following hypothesis were tested: (i) the populations of a given species present the same fluctuation pattern in abundance for different environments and (ii) synchrony is higher when we consider subsets of neighboring environments or those belonging to the same category (e.g., lagoons, rivers). Samplings were performed every three months from February 2000 to November 2002 at 11 sites. To evaluate spatial synchrony, the intraclass correlation coefficient was used. The results showed no significant correlation for the most abundant species, meaning that fluctuation patterns of planktonic cladocerans were asynchronous. Asynchrony indicated that the influence of floods and regional climatic factors was not strong enough to synchronize the populations, suggesting that local factors were more important than regional effects in determining zooplankton abundance patterns. The implications of these results are that the observations from a single environment cannot be extrapolated to other environments in a manner that would allow its use as a sentinel site. This means that a monitoring program for floodplain systems, or at least for the Paraná River floodplain, has to comprise greater spatial extents. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A new pelagic predatory pike cichlid (Teleostei: Cichlidae: Crenicichla) from the C. mandelburgeri species complex with parallel and reticulate evolution

The Crenicichla mandelburgeri species complex from the Middle Paraná shows parallel evolution of ecomorphs to the unrelated C. missioneira species complex from the Uruguay River. In this article, we describe a new species from the C. mandelburgeri species complex that has evolved a parallel morphology and ecology to an unrelated species from the C. missioneira species complex (C. celidochilus). The new species is a pelagic predator that feeds predominantly on fishes and together with C. celidochilus is the only known pelagic species in the large riverine genus Crenicichla. The new species is endemic solely to a small tributary (the Urugua-í) of the Middle Paraná River where it is sympatric and partly syntopic with two other closely related endemic species that, however, differ strongly in their ecomorphologies (one is a generalistic invertivore and the other a specialized molluscivore). Mitochondrial DNA phylogeny finds the new species nested within the widespread C. mandelburgeri. Reduced genome-representation ddRAD analyses, however, demonstrate that this new species is of a hybrid origin and shares ancestry with C. ypo, one of the two studied sympatric species.