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.     

Chromosomal banding in three species of the genus Rineloricaria (Siluriformes, Loricariidae, Loricariinae)

Cytogenetic analyses were conducted in three species: Rineloricaria cadeae, Rineloricaria strigilata and Rineloricaria pentamaculata. The nucleolar organizing regions (NORs) were localized at the terminal position, on the ninth pair of the complement for R. cadeae and R. strigilata, on the eighth and sixth pair of st–a, respectively; and on the fifth pair of the complement for R. pentamaculata, the first pair of st–a. Rineloricaria strigilata and R. pentamaculata showed NOR heteromorphism and polymorphism, respectively. All species showed heterochromatin in the pericentromeric regions and associated with NORs, which were chromomycin A₃ (CMA₃) positive, demonstrating to be GC rich. The results show that NOR is nonconservative in this genus.     

Karyotypic diversity of the armoured catfish genus Hypostomus (Siluriformes: Loricariidae) in the context of its occurrence and distribution

This study taxonomically reviewed the specimens studied by Artoni & Bertollo (1996) and assimilated species of Hypostomus into three groups according to their cytogenetic characteristics, vagility and occurrence environments.     

An integrative approach for species delimitation in the spider genus Grammostola (Theraphosidae,Mygalomorphae)

The mygalomorph genus Grammostola (family Theraphosidae) is endemic to South America. The species Grammostola anthracina is one of the largest spiders in Uruguay and reputed to be the longest lived tarantula in the world. This nominal species has two distinct colour morphs comprising black and reddish‐brown forms with controversial taxonomic status. Here, we present a phylogenetic study based on molecular characters (cytochrome c oxidase subunit I) of haplotypes of G. anthracina and closely related species. Our analysis together with new morphological data and biogeographical information indicates that the two morphs of G. anthracina constitute different species that are not sister to each other. Consequently, a new species, Grammostola quirogai is described, diagnosed and illustrated to encompass the black morph. Phylogenetic relationships and new taxonomic characters for Grammostola species included in this study are discussed.     

Biogeography and species delimitation of the rheophilic suckermouth catfish genus Pseudolithoxus (Siluriformes: Loricariidae), with the description of a new species from the Brazilian Amazon

The rapids-dwelling suckermouth catfish genus Pseudolithoxus was previously only known from the Guiana-Shield-draining Orinoco and Casiquiare river systems of Colombia and Venezuela, but new records have expanded this range considerably further into the Amazon basin of Brazil, and include occurrences from rivers draining the northern Brazilian Shield. These highly disjunct records are now placed in an evolutionary and phylogeographic context using a dated species tree constructed from mitochondrial (Cytb) and nuclear (RAG1) gene sequence data. Due to mito-nuclear discordance, we also delimit the putative species using statistical coalescent models and a range of additional metrics. We infer that at least two species of Pseudolithoxus are present in the Amazon basin: P. nicoi, previously only recorded from the río Casiquiare, but now also reported from the upper rio Negro, and a new species, which we describe herein from south-draining Guiana Shield and north-draining Brazilian Shield. Our data reject a simple model of Miocene vicariance in the group following uplift of the Uaupés Arch separating the Orinoco and Amazon systems, and instead suggest more complex dispersal scenarios through palaeo-connections in the Pliocene and also via the contemporary rio Negro and rio Madeira in the late Pleistocene.

www.zoobank.org/urn:lsid:zoobank.org:pub:46A6BEC1-1A1B-4244-80-A6-FD9CF8DA0384.     

Historical biogeography of the catfish genus Hypostomus (Siluriformes: Loricariidae), with implications on the diversification of Neotropical ichthyofauna

Tropical South America possesses the largest ichthyofauna of any continental region. To test whether palaeohydrological changes may have been the causes of such diversification, the 'hydrogeological' hypothesis, the phylogenetic relationships of 51 representatives of the catfish genus Hypostomus (Siluriformes: Loricariidae) were inferred using mitochondrial D-loop haplotype sequences. Specimens were collected in all main tropical South American rivers systems east to the Andes. The major interrelationships found with the D-loop data were confirmed with a subset of 21 species using complete internal transcribed spacer (ITS) region sequences. The phylogenetic analysis indicate that the genus Hypostomus can be divided into four monophyletic clades. The historical biogeographical analysis of each of these clades allows the identification of seven major cladogenetic events. Using calibrated D-loop and ITS molecular clocks, date estimations were attributed to each of these cladogenetic events allowing a linkage between four of them with documented hydrogeological changes. Comparisons with published distribution patterns of unrelated fish groups indicate that several of the reconstructed and dated hydrogeological-cladogenetic events may have acted at a large scale on the diversification of Neotropical freshwater fish fauna during late Tertiary.     

Description of a new genus and three new species of Otothyrinae (Siluriformes,Loricariidae)

The genus Hisonotus was resurrected as a member of the tribe Otothyrini (actually subfamily Otothyrinae). However, phylogenetic studies based on morphological and molecular data showed that Hisonotus is not monophyletic and independent lineages can be identified, such as the group composed of the species Hisonotus insperatus, Hisonotus luteofrenatus, Hisonotus oliveirai, Hisonotus paresi and Hisonotus piracanjuba, a lineage unrelated to that containing the type species of the genus Hisonotus (Hisonotus notatus). Herein, based in molecular and morphological data, a new genus is described to accommodate the lineage mentioned above, into which are also added three new species. This new genus can be distinguished from other genera of Otothyrinae by the following combination of characters: (1) a pair of rostral plates at the tip of the snout; (2) two large pre-nasal plates just posterior to the rostral plates; (3) a supra-opercular plate that receives the laterosensory canal from the compound pterotic before the preopercle; (4) a well developed membrane at anal opening in females; and (5) a V-shaped spinelet. A key to species of Curculionichthys is provided.     

Chromosomal polymorphism in two species of Hypancistrus (Siluriformes: Loricariidae): an integrative approach for understanding their biodiversity

Structural chromosome changes are widely described in different vertebrate groups and generate genetic, phenotypic and behavioral diversity. During the evolution of loricariids, several rearrangements (fissions, fusions, inversions) seem to have occurred. Hypancistrus, tribe Ancistrini, are highly demanded for fishkeeping around the world. In this tribe, the diploid chromosome number 2n = 52 is considered a synapomorphy, and paracentric-type inversions appear to be involved in the chromosomal evolution of the tribe. The present study investigated the karyotypes of H. zebra and H. cf. debilittera using cytogenetic, classical and molecular tools, as well as DNA barcoding. Data reveal that, although diploid number in both species corroborates the proposed synapomorphy for the tribe, there is a complex karyotype dynamics, reflected in the intense chromosomal polymorphism, resulting from rearrangements involving ribosomal regions (5S and 18S rDNA), which are suggested to be paracentric inversions. Besides, DNA barcode confirms reciprocal monophyletism between the species, validating the existence of two species, only. This scenario, coupled with genomic instability caused by exogenous sequences such as Rex-3 retrotransposons and the species’ sedentary lifestyle, which helps the fast polymorphism fixation, may reflect different phenotypic color patterns in natural populations, as observed in H. cf. debilittera.     

Development of the chondrocranium in the suckermouth armored catfish Ancistrus cf. triradiatus (Loricariidae, Siluriformes)

The chondrocranium of the suckermouth armored catfish Ancistrus cf. triradiatus was studied. Its development is described based on specimens ranging from small prehatching stages with no cartilage visible, to larger posthatching stages where the chondrocranium is reducing. Cleared and stained specimens, as well as serial sections, revealed a cartilaginous skeleton with many features common for Siluriformes, yet several aspects of A. cf. triradiatus are not seen as such in other catfishes, or to a lesser extent. The skull is platybasic, but the acrochordal cartilage is very small and variably present, leaving the notochord protruding into the hypophyseal fenestra in the earlier stages. The ethmoid region is slender, with a rudimentary solum nasi. A lateral commissure and myodomes are present. The larger posterior myodome is roofed by a prootic bridge. The maxillary barbel is supported by a conspicuous cartilaginous rod from early prehatching stages. The ceratohyal has four prominent lateral processes. Infrapharyngobranchials I-II do not develop. During ontogeny, the skull lengthens, with an elongated ethmoid, pointing ventrally, and a long and bar-shaped hyosymplectic-pterygoquadrate plate. Meckel's cartilages point medially instead of rostrally.     

Karyotypic diversity and evolution of Loricariidae (Pisces, Siluriformes)

We present cytogenetic analyses of four fish species, belonging to four Loricariidae subfamilies: Neoplecostomus microps (Neoplecostominae) with 2n=54 chromosomes, Harttia loricariformis (Loricariinae) with 2n=56 chromosomes, Hypostomus affinis (Hypostominae) with 2n=66 chromosomes and Upsilodus sp. (Upsilodinae), with 2n=96 chromosomes. In addition to karyotypes, data on the location of 18s rDNA sites are presented, derived from indirect (silver nitrate impregnation) and direct (FISH) methods. There is only one pair of nucleolar organizing regions (NORs) per species, except in H. affinis. Diversity and NOR macrokaryotypic evolution in the species analyzed are discussed in relation to the evolution of the Loricariidae as a whole. In addition, a revision of the cytogenetic data available for this family is presented.     

Cytogenetic analysis of five Hypostomus species (Siluriformes, Loricariidae)

In this work, we analyzed the karyotypes of five Hypostomus species. Hypostomus cf. heraldoi, from the Mogi-Gua?u River, had 2n = 72 chromosomes, with a nucleolar organizer region (NOR) in one chromosomal pair. Hypostomus regani, from the Mogi-Gua?u River had 2n = 72 chromosomes with NORs in two chromosomal pairs. Hypostomus sp., from the Mogi-Gua?u River basin, had 2n = 68 chromosomes, with NORs in two chromosomal pairs. Hypostomus aff. agna, from Cavalo Stream, had 2n = 74 chromosomes with NORs in two chromosomal pairs. Hypostomus cf. topavae, from Carrapato Stream, had 2n = 80 chromosomes, with NORs in two chromosomal pairs. Hypostomus species showed marked diversity in the karyotypic formula, which suggested the occurrence of several Robertsonian rearrangements and pericentric inversions during the evolutionary history of this genus. This hypothesis was supported by the occurrence of a large number of uniarmed chromosomes and multiple NORs in a terminal position in most species and may be a derived condition in the Loricariidae.     

Parotocinclus jacksoni,a new hypoptopomatine catfish (Siluriformes: Loricariidae) from the Rio Mamanguape basin,north-eastern Brazil

A new species of Parotocinclus is described from the Rio Mamanguape basin, in the State of Paraíba, north-eastern Brazil. The new species can be distinguished from all of its congeners, except for P. bahiensis, P. cesarpintoi, P. jumbo, P. nandae and P. spilosoma, by the presence of an abdomen covered by a few small and dispersed platelets (vs. an abdomen entirely covered by large plates in adult individuals or the absence of plates in that region). The new species differs from those mentioned above with respect to several features, such as an exposed pectoral girdle and supporting odontodes medially and laterally, the number of premaxillary and dentary teeth, odontodes covering only the lateral portion of the cleithrum and the absence of irregular golden lines on the head and body (colour in vivo). The new species was collected only in the upper and middle portions of the Rio Mamanguape basin, suggesting a geographic distribution restricted to the Caatinga biome.     

A New Species of Tiger Pleco Panaqolus (Siluriformes: Loricariidae) from the Xingu Basin,Brazil

Panaqolus tankei is described from the Xingu River, Brazil. The new species is diagnosed from P. albomaculatus, P. dentex, P. nix, P. nocturnus, and P. koko by its color pattern consisting of dark and light diagonal bars on the body and bands on the fins (vs. body and fins without bars or bands); from P. albivermis, P. maccus, and P. purusiensis by the width of the dark bars being more or less the same of the light bars (vs. dark bars at least two or three times wider than light bars) and from P. changae by the absence of vermiculation on the head (vs. vermiculation present on head). The new species differs from P. gnomus by the orientation of the bars from posterodorsal to anteroventral direction (vs. anterodorsal to posteroventral direction), and from P. claustellifer by the orientation of the bands in the dorsal fin that are not parallel to the margin (vs. parallel to the margin). The barcoding region (COI) was sequenced for the new species, sequences were deposited in GenBank and were compared with congeners from other drainages. With regard to the current construction of a hydroelectric power plant (a so-called mega dam) in the Xingu River, herewith we increase knowledge of the river Xingu’s ichthyofauna and, thus improve the assessment of the impacts of that construction on the river.     

Species delimitation in Neotropical fishes of the genus Characidium (Teleostei,Characiformes)

Neotropical darters of the genus Characidium have a complex systematic history with several examples of sympatry throughout their distribution range in Neotropical freshwaters. Although various species within the genus have been used as models to investigate chromosomal evolution and biogeography, species boundaries and relationships still remain uncertain. Here, we use mitochondrial DNA sequences to perform species delimitation analyses within Characidium and test previous hypotheses of species richness within the Characidium zebra complex and among sympatric morphotypes of C. alipioi. Results indicate high genetic distances within tested species complexes and revealed the presence of strongly supported lineages such as the large C. lauroi group from southeastern Brazil. This suggests that the evolutionary history of these groups may be correlated with biogeographic history. Analyses also reveal that three geographically isolated populations of C. zebra represent a single species, leading us to reject prior hypothesis of multiple species. Species delimitation using mitochondrial data strongly supports the presence of two sympatric species within C. alipioi in southeastern Brazil despite limited morphological variation and conserved chromosomal patterns. These results provide a framework to further the study of systematics and evolution within Characidium.     

Trends in the karyotype evolution of Loricariidae fish (Siluriformes)

Six species of Loricariidae belonging to the subfamilies Hypostominae (Hypostomus emarginatus, Rhinelepsis aspera, Pogonopoma wertheimeri), Ancistrinae (Panaque cf. nigrolineatus, Hemiancistrus sp.) and Loricariinae (Sturisoma cf. nigrirostrum) were studied cytogenetically. The results show that 2n = 54 represents the basal diploid number for this fish family. Different trends in the karyotypic evolution can be seen among the subfamilies: Hypostominae and Loricariinae species present diversified karyotypic macrostructures, while the Ancistrinae appear to show more conserved karyotypes. Among the Hypostominae, the genus Hypostomus had a wide karyotypic variation (2n = 52 to 80), where centric fissions seem to play an important role in this chromosomal divergence. The nucleolar organizing regions were diversified, and occurrence of multiple NORs was frequent. Heteromorphic chromosomes belonging to distinct sex chromosome systems can also occur infrequently among the Loricariidae.     

A new species of the leopard pleco genus Pseudacanthicus (Siluriformes: Loricariidae) from the Rio Xingu,Brazil

The genus Pseudacanthicus comprises six valid species distributed in the Amazon basin and Caribbean coastal drainages from Guyana to French Guiana: P. serratus, P. fordii, P. histrix, P. spinosus, P. leopardus and P. pitanga. A new species of Pseudacanthicus is described from the Rio Xingu Basin, distinguished from its congeners by the following combination of characters: presence of anastomose dark blotches forming continuous zigzag bands alongside longitudinal keels; presence of dark blotches on ventral surface of body and head; all fins with orange to red colour on unbranched rays and sometimes subsequent branched rays. Brief comments on ornamental fisheries and conservation of the new species are also provided.     

Spermiogenesis and sperm ultrastructure in ten species of Loricariidae (Siluriformes, Teleostei)

The current study describes the ultrastructural characteristics of spermatogenesis, spermiogenesis, and spermatozoa in specimens of siluriform taxa Neoplecostominae, Hypoptopomatinae, Otothyrinae, Loricariinae, and Hypostominae. Our data show that the characteristics of spermatogenesis and spermiogenesis and spermatozoa ultrastructure of Neoplecostominae are more common to Hypoptopomatinae and Otothyrinae than to Loricariinae and Hypostominae. Furthermore, Loricariinae and Hypostominae have more characteristics in common than with any other group of Loricariidae. These data reinforce the phylogenetic hypotheses of relationships among the subfamilies of Loricariidae. Considering the available data in Loricarioidei, Loricariidae presents ultrastructural characteristics of spermatogenesis and spermiogenesis that are also observed in Astroblepidae, its sister group. However, the most of the characteristics of spermatozoa ultrastructure found in Astroblepidae are also observed in Scoloplacidae, the sister group of a clade composed of Astroblepidae and Loricariidae.