Unraveling the systematics and evolution of the 'Geophagus' brasiliensis (Cichliformes: Cichlidae) species complex

The role of dispersal of repetitive DNAs in the diversification of bristlenose plecos (Loricariidae, Hypostominae, Ancistrus) from South Atlantic Coastal drainages

Sea-level changes during the Pleistocene and the geomorphological history have largely molded the intricate shaping of coastal drainages in Eastern South America. Therefore, freshwater fishes from this region are promising models to infer how riverine isolation and reconnections affected their genetic diversification and geographic distribution. In the present study, we provided a detailed cytogenomic analysis of Ancistrus multispinis and Ancistrus brevipinnis, including the physical mapping of repetitive DNA classes, to verify whether chromosome differentiation would be related to the split between two major watersheds in Southern Brazil. Both species of Ancistrus shared the same modal diploid number (2n=52) and karyotype formulae (14 metacentric, 8 submetacentric and 30 subtelo/acrocentric chromosomes), besides single and terminal 18S ribosomal cistrons, (CGG)10 microsatellite sequences interspersed with heterochromatin in nucleolar organizer regions and a dispersed content of (AC)15 and (GT)15 microsatellites. In turn, the patterns of heterochromatin distribution, number of (GAG)10 microsatellites and 5S rDNA clusters diverged between both taxa. Most likely, these microstructural differences were determined by independent evolutionary processes, strongly associated to the geographic isolation between watersheds. Furthermore, the mapping of repetitive DNAs revealed a dynamic reorganization of genomes of Ancistrus, being useful for the taxonomic disambiguation in this complex group of Neotropical fish.

Ichthyofauna from tributaries of the Paranapanema River basin, Cerqueira César municipality, southeastern Brazil

Here we provide an ichthyofaunistic inventory of the Cerqueira César municipality, in the middle Paranapanema River drainage, upper Paraná River basin, São Paulo State, southeastern Brazil. Collections were carried out in 10 streams and in the Novo River, an important watercourse in the Paranapanema River basin. We caught a total of 808 individuals comprising 49 fish species. Among our main findings-in addition to the high species richness in the sampled region-was the capture of a probably undescribed species of Cambeva and the non-native poeciliid Poecilia reticulata. Some individuals were not identified accurately at the species level, requiring future evaluations. Our study fills an important gap on the ichthyofauna of the municipality of Cerqueira César and may, in the future, assist in new studies on impacts on waterbodies in the studied region.

Freshwater fishes of the Northeastern Mata Atlântica ecoregion, Brazil: an updated checklist with distributional patterns of a highly endemic ichthyofauna

We present an annotated and updated checklist of freshwater fish species occurring in the Northeastern Mata Atlântica ecoregion (NMAF), Eastern Brazil. A total of 305 native freshwater fish species are documented for this ecoregion, of which 210 are endemic. Distribution maps of 298 species are provided. There is a general pattern of increased sampling intensity in coastal zones, gradually diminishing towards the west as elevation increases. A bioregionalization algorithm identified four biogeographic units in the NMAF ecoregion: Northern Bioregion, Central Bioregion, Coastal Tablelands Bioregion and Southern Bioregion. The heterogeneous nature of the ichthyofauna in this area, along with the significant faunal overlap observed between NMAF and adjacent ecoregions, suggests that the approach of ecoregion delimitation may not be fully congruent with the current faunal compositions. This underscores the need for novel regionalization approaches that reinforce outcomes consistent with the diversity patterns evident within the ecoregion.

The fish collection of Jos Mariano da Conceio Veloso (17421811) and the beginning of ichthyological research in Brazil, with a taxonomic description of the extant specimens

Two Portuguese institutions, the Museu Maynense da Academia das Cincias de Lisboa (ACL), and the Museu da Cincia da Universidade de Coimbra (MCUC), house a collection of 85 dried fish specimens prepared in what can be called a fish-herbaria following a process similar to that developed by the Dutch naturalist Johan Frederic Gronovius (16901762). These specimens date back to the late eighteenth century and represent Brazilian taxa. Previous authors assumed that they were part of the collections amassed by the Brazilian-Portuguese naturalist Alexandre Rodrigues Ferreira (17561815) during his philosophical voyage to the Amazon. Here we present a review of these specimens, suggesting that they belonged to Friar Jos Mariano da Conceio Veloso (17421811) and describe the history of dispersal of these collections up the present day. A total of 58 species in 50 genera, 32 families and 19 orders are represented in the collection. Only 8.6% of these specimens represent freshwater species, while 91.4% are marine or brackish water species. The present known distribution of these taxa is focused on southwestern Brazil, which agrees with the area where Veloso collected natural history specimens. A good percentage of the species were undescribed at the time Veloso collected them, and had they been published by him, would have had priority over species described decades later by famous eighteenth and nineteenth century ichthyologists. We also present a brief discussion on the challenges and opportunities of studying historical natural history specimens, with special focus on those amassed during the late eighteenth and early nineteenth century by Brazilian-Portuguese naturalists.

Genetic Diversity in Natural Populations of the Near-Threatened Species Lignobrycon myersi (Characiformes, Triportheidae): Implications for Species Conservation

The river basins of Brazil contain a highly diverse ichthyofauna of remarkable endemism, including several threatened species. Accordingly, Lignobrycon myersi is a fish species distributed only in a few rivers from the state of Bahia, northeastern Brazil. Since this species is classified as Near Threatened and is poorly studied, efforts to understand the genetic structure of populations and putative cryptic forms should help define efficient strategies of management and conservation. Herein, the molecular identification and the population genetic diversity of specimens of L. myersi across their range (Almada, Contas, and Cachoeira river basins) were assessed using mitochondrial markers (16S rDNA and D-Loop, respectively). The inferences based on phylogenetics, genetic distance, and species delimitation methods invariably identified all samples as L. myersi. In addition, sequencing of D-loop fragments revealed significant haplotype diversity and a considerable level of population genetic structure. Despite their geographic isolation, these data suggested that populations from Almada and Contas rivers represent a single evolutionary lineage that could be managed as a whole. In contrast, the population from Cachoeira River was highly differentiated from the others and should be managed separately as a unique and endemic unit, particularly focused on the conservation of native habitats.

Conjectures and refutations: Species diversity and phylogeny of Australoheros from coastal rivers of southern South America (Teleostei: Cichlidae)

Morphological and genetic analyses of species of Australoheros focusing on those distributed in coastal rivers from the Rio de La Plata north to the Rio Buranhém, support recognition of 17 valid species in the genus. Eight species are represented in coastal rivers: A acaroides, A. facetus, A. ipatinguensis, A. oblongus, A. ribeirae, and A. sanguineus are validated from earlier descriptions. Australoheros mboapari is a new species from the Rio Taquari in the Rio Jacuí drainage. Australoheros ricani is a new species from the upper Rio Jacuí. Specimens from the Rio Yaguarón and Rio Tacuary, affluents of Laguna Merín, and tributaries of the Rio Negro, tributary of the Rio Uruguay are assigned to A. minuano pending critical data on specimens from the type locality of A. minuano. Australoheros taura is a junior synonym of A. acaroides. Australoheros autrani, A. saquarema, A. capixaba, A. macaensis, A. perdi, and A. muriae are junior synonyms of A. ipatinguensis. Heros autochthon, A. mattosi, A. macacuensis, A. montanus, A. tavaresi, A. paraibae, and A. barbosae, are junior synonyms of A. oblongus. Heros jenynsii is a junior synonym of A. facetus.

Ecology and the origin of non-ephemeral species

AbstractResearch over the past three decades has shown that ecology-based extrinsic reproductive barriers can rapidly arise to generate incipient species-but such barriers can also rapidly dissolve when environments change, resulting in incipient species collapse. Understanding the evolution of unconditional, "intrinsic" reproductive barriers is therefore important for understanding the longer-term buildup of biodiversity. In this article, we consider ecology's role in the evolution of intrinsic reproductive isolation. We suggest that this topic has fallen into a gap between disciplines: while evolutionary ecologists have traditionally focused on the rapid evolution of extrinsic isolation between co-occurring ecotypes, speciation geneticists studying intrinsic isolation in other taxa have devoted little attention to the ecological context in which it evolves. We argue that for evolutionary ecology to close this gap, the field will have to expand its focus beyond rapid adaptation and its traditional model systems. Synthesizing data from several subfields, we present circumstantial evidence for and against different forms of ecological adaptation as promoters of intrinsic isolation and discuss alternative forces that may be significant. We conclude by outlining complementary approaches that can better address the role of ecology in the evolution of nonephemeral reproductive barriers and, by extension, less ephemeral species.

A new species of Geophagus (Teleostei: Cichlidae): Naming a cichlid species widely known in the aquarium hobby as 'Geophagus sp. Tapajos red head'

A new species of Geophagus sensu stricto is described from the Tapajos River basin, Brazil, elevating the number of species of the genus to 21. The new species is of commercial importance and is known in the aquarist trade as Geophagus 'red head'. The new species is diagnosed using an integrative approach, based on mitochondrial DNA analysis along with morphological evidence. The new species is distinguished from all congeners by the absence of markings on the head, the bar pattern composed by nine vertical bars on the flanks and the presence of distinct longitudinal bands in the caudal fin. Additionally, it shows a genetic distance of at least 2.0% in cytochrome b gene sequences from its closest congeners. Molecular analysis including most genera of Cichlidae from South America corroborates that the new species belongs to the group of Geophagus sensu stricto.

Multi-locus phylogeny and species delimitations of the striped-back shrew group (Eulipotyphla: Soricidae): Implications for cryptic diversity, taxonomy and multiple speciation patterns

The striped-back shrew group demonstrates remarkable variation in skull and body size, tail length, and brightness of the dorsal stripe; and karyotypic and DNA variation has been reported in recent years. In this study, we investigated the phylogenetic structure of the group, as well as speciation patterns and demographic history in Mountains of Southwestern China and adjacent mountains, including the southern Himalayas, Mts. Bashan, Wushan, and Qinling. We sequenced a total of 462 specimens from 126 localities in the known range of the group, which were sequenced and analyzed based on 6.2 kb of sequence data from two mitochondrial, six nuclear, and two Y chromosome markers. Phylogenetic analyses of the concatenated mtDNA data revealed 14 sympatric and independently evolving lineages within the striped-back shrew group, including Sorex bedfordiae, S. cylindricauda, S. excelsus, S. sinalis and several cryptic species. All concatenated data (ten genes) showed a consistent genetic structure compared to the mtDNA lineages for the group, whereas the nuclear and the Y chromosome data showed a discordant genetic structure compared to the mtDNA lineages for the striped-back shrew group. Species delimitation analyses and deep genetic distance clearly support the species status of the 14 evolving lineages. The divergence time estimation suggested that the striped-back shrew group began to diversify from the middle Pleistocene (2.34 Ma), then flourished at approximately 2.14 Ma, followed by a series of rapid diversifications through the Pleistocene. Our results also revealed multiple mechanisms of speciation in the Mountains of Southwestern China and Adjacent Mountains with complex landscapes and climate. The uplifting of the Qinghai-Tibetan Plateau, Quaternary climate oscillations, riverine barriers, ecological elevation gradients, topographical diversity, and their own low dispersal capacity may have driven the speciation, genetic structure, and phylogeographic patterns of the striped-back shrew group.

Otolith shape analysis supports three cryptic species in the Stellifer punctatissimus complex (Acanthuriformes: Sciaenidae)

Abstract Sciaenidae species (croakers and drums) are known for specializations in their sensory apparatus, such as otoliths and lateral line. Within this family, some Stelliferinae members remain taxonomically unresolved due to their cryptic aspects and low phenotypic disparities. Stellifer punctatissimus comprises a species complex putatively formed by three species on morphological grounds, but molecular data have indicated only two evolutionary lineages. Herein, we tested the hypothesis that this complex is composed of Stellifer gomezi (GM), S. menezesi (MN), and S. punctatissimus (PC), using the otolith shape and morphology to differentiate them. Seventy-seven sagittal otoliths (GM = 30, MN = 30, PC = 17) were photographed to outline the otolith contour by Elliptical Fourier descriptors. Ten otoliths for each group were used to detect shape variation in the sulcus acusticus through semilandmarks. Differences in otolith shape contour were recorded among the species by PERMANOVA (Pseudo-F = 4.02, df = 2, p < 0.001) and corroborated by the Linear Discriminant Analysis, which demonstrated three partially segregated groups with satisfactory re-classification rates. A larger sulcus acusticus (GM and MN), rounded projection (PC), and distinct rectangularity pattern were also recorded. Our results support the morphological hypothesis and thus contribute to narrowing the taxonomic gaps in Sciaenidae.

Prey selectivity of the invasive largemouth bass towards native and non-native prey: an experimental approach

Abstract Non-native predators are known to cause ecological impacts through heightened consumption of resources and decimation of native species. One such species is Micropterus salmoides. Often introduced for sport fishing worldwide; it has been listed by International Union for Conservation of Nature and Natural Resources as one of the 100 of the world’s worst invasive species. Whilst impacts conferred towards native prey are well known, its relationship with other non-native species has received much less attention. Therefore, the aim of this study was to experimentally investigate the feeding preference of M. salmoides towards native prey (Geophagus iporangensis) compared to non-native prey (Oreochromis niloticus and Coptodon rendalli) using comparative consumption and the Manly-Chesson selectivity index. We found a higher consumption by M. salmoides towards the non-native prey and a tendency for this non-native preference to increase when prey availability increased. Our results are in line with the hypothesis that the invasion of the non-native predator can be facilitated by the high abundance and reproductive rate of the non-native prey. This is relevant considering the interaction of multiple invaders in an ecosystem, in particular environments modified by humans. Interspecific relationships are complex and their understanding is necessary for environmental management decision-making.

Mapping the hidden diversity of the Geophagus sensu stricto species group (Cichlidae: Geophagini) from the Amazon basin

South American freshwater ichthyofauna is taxonomically the most diverse on the planet, yet its diversity is still vastly underestimated. The Amazon basin alone holds more than half of this diversity. The evidence of this underestimation comes from the backlog of morphologically distinct, yet undescribed forms deposited in museum collections, and from DNA-based inventories which consistently identify large numbers of divergent lineages within even well-studied species groups. In the present study, we investigated lineage diversity within the Geophagus sensu stricto species group. To achieve these objectives, we analyzed 337 individuals sampled from 77 locations within and outside the Amazon basin representing 10 nominal and six morphologically distinct but undescribed species. We sequenced the mitochondrial cytochrome c oxidase subunit I (COI) and delimited lineages using four different single-locus species discovery methods (mPTP-15 lineages; LocMin-14 lineages; bGMYC-18 lineages; and GMYC-30 lineages). The six morphologically distinct but undescribed species were also delimited by the majority of the species discovery methods. Five of these lineages are restricted to a single collection site or a watershed and their habitats are threatened by human activities such as deforestation, agricultural activities and construction of hydroelectric plants. Our results also highlight the importance of combining DNA and morphological data in biodiversity assessment studies especially in taxonomically diverse tropical biotas.

Disentangling the complex alpha taxonomy of Andean populations of Ctenomys (Rodentia: Ctenomyidae) from northern Patagonia: the need for extensive sampling in heterogeneous landscapes

In the Andean portion of northern Patagonia, populations of Ctenomys are found from low-elevation plains to high-elevation meadows and valleys. Despite their prevalence, the taxonomy of these subterranean rodents remains poorly resolved. Using genetic and morphological data obtained from museum specimens and animals collected in the field, we examined the taxonomy of Ctenomys from southwestern Mendoza Province, Argentina. Our analyses suggest the presence of at least five species of Ctenomys within the study area. The highest, innermost portion of the Andes is occupied by C. maulinus. To the east, the mountains and foothills are inhabited by two forms associated with the “mendocinus” and the “magellanicus” lineages, respectively. The former appears to be a local variant of C. emilianus, while the latter is sister to C. pontifex. Although C. pontifex was not encountered during our field sampling, it remains a valid species that likely is restricted to the isolated Valle Hermoso in westernmost Mendoza Province. In addition, we report an undescribed form from Las Leñas Valley that is associated with the “mendocinus” lineage. This complex alpha taxonomic scenario occurs within less than one degree of latitude, thereby highlighting the need to conduct detailed field collections to improve our knowledge of the systematics of Ctenomys.

From the headwaters to the Iguassu Falls: Inventory of the ichthyofauna in the Iguassu River basin shows increasing percentages of nonnative species

Abstract: Knowledge of the ichthyofauna of a hydrographic basin is the minimum necessary condition for the implementation of any measures for the exploration, management or preservation of water and fishing resources. Despite its relevance, the number of fish species across the Iguassu River basin is still uncertain. Thus, the objective of this study was to compile the fish species that occur in the extensive stretch of the basin above the Iguassu Falls. In addition, we recorded the level of threat of extinction for native species, the origin of nonnative species, and their main vectors of introduction. To achieve this goal, a survey was carried out through consultations with ichthyological collections as well as online databases. Also, a literature review was conducted using the search platforms Thomson Reuters, SciELO and Elsevier’s ScienceDirect to locate all articles published by March 2020 that addressed the topic “ichthyofauna in the Iguassu River basin”. The survey compiled a total of 133 fish species distributed in nine orders, 29 families and 72 genera. Seventy-nine fish species were recorded that occur throughout the entire length of the basin, 119 species that occur in the hydrographic units of the middle and lower Iguassu River (40 exclusive) and 93 species that occur in the hydrographic unit of the upper Iguassu River (14 exclusive). The endemism rate shown here for the Iguassu River basin (approximately 69%) contrasts with the 40 nonnative fish species recorded (approximately 30% of the total species in the basin). Successive impoundments, reductions in habitat quality and the increase in the number of nonnative species are the main threats to native species, especially to the endemic species; approximately 20% of these species were listed in some category of threat of extinction. We emphasize that constant monitoring of ichthyofauna is necessary to discover putatively undescribed species, as well as for the application of management strategies to mitigate the negative effects and promote the control of the spread of nonnative species.