The main objectives of this study are estimate a species-dense, time-calibrated molecular phylogeny of Hypoptopomatinae, Neoplecostominae, and Otothyrinae, which together comprise a group of armoured catfishes that is widely distributed across South America, to place the origin of major clades in time and space, and to demonstrate the role of river capture on patterns of diversification in these taxa. We used maximum likelihood and Bayesian methods to estimate a time-calibrated phylogeny of 115 loricariid species, using three mitochondrial and one nuclear genes to generate a matrix of 4,500 base pairs, and used parametric biogeographic analyses to estimate ancestral geographic ranges and to infer the effects of river capture events on the geographic distributions of these taxa. Our analysis recovered Hypoptopomatinae, Neoplecostominae, and Otothyrinae as monophyletic with strong statistical support, and Neoplecostominae as more closely related to Otothyrinae than to Hypoptopomatinae. Our time-calibrated phylogeny and ancestral-area estimations indicate an origin of Hypoptopomatinae, Neoplecostominae, and Otothyrinae during the Lower Eocene in the Atlantic Coastal Drainages, from which it is possible to infer several dispersal events to adjacent river basins during the Neogene. In conclusion we infer a strong influence of river capture in: (1) the accumulation of modern clade species-richness values; (2) the formation of the modern basin-wide species assemblages, and (3) the presence of many low-diversity, early-branching lineages restricted to the Atlantic Coastal Drainages. We further infer the importance of headwater stream capture and marine transgressions in shaping patterns in the distributions of Hypoptopomatinae, Neoplecostominae and Otothyrinae throughout South America.

Freshwater fish evolution has been shaped by changes in the earth's surface involving changes in the courses of rivers and fluctuations in sea level. The main objective of this study is to improve our knowledge of the evolution of loricariids, a numerous and adaptive group of freshwater catfish species, and the role of geological changes in their evolution. We use a number of different phylogenetic methods to test the relationships among 52 representative taxa within the Neoplecostominae using 4676 bps of mitochondrial and nuclear DNA. Our analysis revealed that the subfamily Neoplecostominae is monophyletic, including Pseudotocinclus, with three lineages recognized. The first lineage is composed of part of Pareiorhina rudolphi, P. cf. rudolphi, and Pseudotocinclus; the second is composed of Isbrueckerichthys, Pareiorhaphis, Kronichthys, and the species Neoplecostomus ribeirensis; and the third is composed of Pareiorhina carrancas, P. cf. carrancas, Pareiorhina sp. 1, a new genus, and all the species of the genus Neoplecostomus, except N. ribeirensis. The relaxed molecular clock calibration provides a temporal framework for the evolution of the group, which we use for a likelihood-based historical biogeographic analysis to test relevant hypotheses on the formation of southeast Brazil. We hypothesize that headwater capture events and marine regressions have shaped the patterns of distribution within the subfamily Neoplecostominae throughout the distinct basins of southeast Brazil.

ABStRACt. Hypostomus sp 3-Córrego Salobrinha NUP 4247 and Hypostomus sp 2-Rio Perdido NUP 4249, collected in the Planalto da Bodoquena, Paraguay River basin, Brazil, were characterized cytogenetically. Hypostomus sp 3-Córrego Salobrinha showed two modal numbers. This polymorphism consists of the presence of two extrachromosomes. It was not possible to define the diploid number in four specimens, where cell lineages had 2n = 83 and 2n = 84 chromosomes in one individual, and 2n = 82, 2n = 83 and 2n = 84 chromosomes in the others. These results reveal the existence of a genetic mosaic due to the occurrence of one or two extrachromosomes in this species. Hypostomus sp 2-Rio Perdido NUP 4249 showed a 2n = 84, FN = 106 with size heteromorphism in one pair of chromosomes stained with AgNO 3 . In both species, C banding showed a pattern of heterochromatin distribution with a few small bands in the centromeric and pericentromeric regions coinciding with chromomycin A 3 staining. Until now, the major diploid number for the genus Hypostomus was 2n = 80, but the species studied here had chromosomes that in- creased this number and the variation for this genus. Our results are also the first cytogenetic data on Hypostomus from the Paraguay River basin.

Genetic and morphometric analysis of three species of the genus Hypostomus Lacépède, 1803 (Osteichthyes: Loricariidae) from the Rio Iguaçu basin (Brazil)." Revue suisse de zoologie 106, 91-105.

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.

Phylogenetic relationships and identification of species of the genus Hypostomus is still unclear. Considering this, cytogenetics may prove itself as an important tool in understanding the systematic of this genus. Reviews in Hypostomus indicate that the diploid number ranges from 54 to 84 chromosomes, and the increase in diploid number has been associated to higher percentages of subtelocentric and acrocentric chromosomes. Although there is a high number of species in the genus, there are relatively few papers concerning Hypostomus cytogenetics, and most of the data is published as grey literature. With the aim to understand the chromosomal evolution in the genus (correlation between diploid number x chromosomes types), H. ancistroides and H. topavae from the Piquiri River, Upper Paraná River basin, were cytogenetically analyzed, and the diploid number observed was 68 and 80 chromosomes, respectively. Additional data on the diploid number and chromosome formulae was compiled from papers (27 analyses) and abstracts from grey literature (77 analyses). Our analysis shows no correlation between chromosome numbers and percentages of subtelocentric and acrocentric chromosomes for most of the species, since there is considerable variation between these percentages even between species with the same diploid number, indicating that the proportion of chromosome types is not always associated to diploid numbers.

A new Hypostomus species is described from the rio Cuiabá, upper rio Paraguay basin, Mato Grosso State, Brazil. The new species is distinguished from all other Hypostomus species, with exception of young specimens of H. latifrons, by the presence of a wide dark transverse bars on laterals of body and fins; and conspicuous dark vermiculations on abdominal region. From H. latifrons it differs by having just one pre-dorsal plate surrounding supraoccipital bone and by the maintenance of the dark saddles in adults. Added to the other fish species recently described from the upper rio Paraguay basin, this work helps to highlight that the region still functions as a potential source of new species.Uma espécie nova de Hypostomus é descrita do rio Cuiabá, bacia do alto rio Paraguai, Estado do Mato Grosso, Brasil. A espécie nova é diagnosticada de todas as outras congêneres, com exceção de H. latifrons, pela presença de amplas barras escuras transversais nas laterais do corpo e nadadeiras, e pelas conspícuas vermiculações escuras na região abdominal. De H. latifrons ela difere por ter somente uma placa pré-dorsal margeando o osso supraoccipital e pela manutenção das barras escuras transversais nos adultos. Somada a outras espécies de peixes recentemente descritas na bacia do alto rio Paraguai, este trabalho demonstra que a região ainda funciona como uma fonte potencial de espécies novas.

In an allozyme electrophoresis survey of 15 hypostomine species from the Itaipu Hydroelectric Reservoir, 25 loci from 14 enzyme systems were scored. Allozyme data allowed recording diagnostic genetic markers for all species analyzed and for some species groups within Hypostomus, a taxon which is taxonomically still unresolved in the Upper Rio Paraná basin. The mean expected heterozygosity of the species was considerably variable and hypotheses to tentatively explain this variation are discussed. A cladogram based upon the allelic frequencies of the species analyzed was produced by the continuous maximum likelihood method: Rhinelepis aspera and M. parananus were separated from the species of Hypostominae by a long branch length. Pterygoplichthys anisitsi was the sister of all the representatives of the genus Hypostomus. Within Hypostomus, two main clades were produced: in the first, H. cochliodon was the sister of the species comprising the H. plecostomus group, and in the second, the tree showed the following relationships: (H. albopunctatus (H. regani + Hypostomus sp. 3) + (H. margaritifer (H. microstomus (Hypostomus sp. 1 (H. ternetzi + Hypostomus sp. 2)). Hypostomus ternetzi and Hypostomus sp. 2 are referred to here as representatives of the H. ternetzi group.