Monthly Archives: January 2020

Phylogenetic relationships of a new genus and species of stevardiine fish (Characiformes: Characidae: Stevardiinae) from the Río Amazonas basin, Peru

James A. Vanegas‐Ríos, Dario R. Faustino‐Fuster, Vanessa Meza‐Vargas, Hernán Ortega

Abstract

Varicharax nigrolineatus, a new genus and species of stevardiine fish, is described from the Río Amazonas basin, Peru, based on a comprehensive phylogenetic comparison with other characids. Two data sets (A: combined morphological and molecular matrix, 474 species and 6,653 characters; B: morphological matrix, 216 species and 524 characters) were used to estimate the phylogenetic relationships of the new genus. Morphological and molecular data from these data sets were taken from two previously published matrices on characids. Varicharax nigrolineatus is phylogenetically diagnosed by 18 autapomorphies in total (from both data sets), which are related to different anatomical characteristics of the neurocranium, body, and fins. Furthermore, V. nigrolineatus can be easily differentiated from all characids (except Acrobrycon in part) by the following combination of characters: the presence of a hypertrophied caudal‐fin squamation on the lower caudal‐fin lobe forming a remarkable pouch‐like structure, consisting of multiple series of large adjacent scales (being almost similar or slightly more pronounced in males than in females), the presence of caudal‐fin bony hooks on the lower lobe in adult males, complete lateral line, and a dark mid‐lateral stripe that extends from the posterior border of the head to caudal peduncle. In the resulting topologies from both data sets, the phylogenetic placement of V. nigrolineatus was well supported within Stevardiinae. Additionally, V. nigrolineatus was resolved within the tribe Stevardiini as sister group of a clade formed by Chrysobrycon + Pseudocorynopoma and Corynopoma + Gephyrocharax in the final hypothesis from the combined data set, whereas in the final topology from the morphological data set, V. nigrolineatus was placed as sister group of a clade comprised of Acrobrycon and the Stevardiini without Argopleura.
https://onlinelibrary.wiley.com/doi/full/10.1111/jzs.12346

Phylogenetic relationships of Varicharax nigrolineatus within Stevardiinae obtained from the data set A (combined molecular and morphological matrix) (L = 58,206; Fit = 968.263752) using extended implied weighting. Node numbers are indicated above branches. Support values are presented below branches and separated by a slash (Absolute frequency/GC value). Full tree available as Figure S1

Varicharax nigrolineatus, (a) MUSM 60288, male, holotype, 36.1 mm SL; (b) MUSM 58235, female, paratype, 27.9 mm SL, collected with holotype

First record of Astyanax bifasciatus Garavello & Sampaio, 2010 (Teleostei, Ostariophysi, Characidae) in the Piquiri river basin, upper Paraná river basin

Mayara P. Neves, Priscilla C. Silva, Rosilene L. Delariva, Clarice B. Fialho, Andre L. Netto-Ferreira

Abstract

Astyanax bifasciatus Garavelo & Sampaio, 2010 was originally described as endemic to the Iguaçu river basin. Between March 2017 and January 2018, specimens of A. bifasciatus were sampled during expeditions to headwater streams of the Piquiri river basin, upper Paraná river basin. The identification was confirmed both by morphological and molecular analyses, representing, therefore, the first record of the species outside of the basin of the Iguaçu River. In addition, the lack of structuring in the haplotype network confirms that the representatives of A. bifasciatus from both basins appear to comprise a single population.

Keywords: Distribution range, DNA barcode, endemicity, headwater streams, species identification

https://checklist.pensoft.net/article/47628/

Figure 2. Astyanax bifasciatus. A. UFRGS 26235, 85.0 mm SL, Arquimedes stream, lower Iguaçu river basin, Paraná, Brazil. B. UFRGS 26231, 91.3 mm SL, Carreira stream, Piquiri river basin, upper Paraná river basin, Paraná, Brazil.

Fishes community composition and patterns of species distribution in Neotropical streams

Laísa Wociechoski Cavalheiro  & Clarice Bernhardt Fialho

ABSTRACT:

The ichthyofauna of streams in the Neotropical region is not yet fully known. This study aims to investigate the ichthyofauna composition of six streams of the Ijuí River sub-basin, Rio Grande do Sul State, inserted in the Uruguay River basin, as to contribute to the knowledge of fishes species richness and distribution in the south of Brazil. Sampling was carried out between July 2015 and May 2016, bimonthly, using the technique of electric fishing to collect the fishes. Spatial variations (per sampled stream) in the ichthyofauna composition were tested with a permutational multivariate analysis of variance. In total, we collected 5,029 individuals from 55 species, 13 families and five orders. From these species, 17 are endemic to the Uruguay River basin. Five species alone represented approximately 70% of the ichthyofauna abundance sampled. Our hypothesis that the fish community composition is not homogeneous along the streams sampled was confirmed and we observed that species complexity increases from the upstream closest area to the downstream according to the river continuum concept.

Keywords: Abundance; Characidae; Heptapteridae; Loricariidae; Richness; Uruguay River basin

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1676-06032020000100302

Figure 1 Location of the sampled streams in the Ijuí River sub-basin and its respective position into the Uruguay River hydrographic basin, Brazil.

Biogeography, habitat transitions and hybridization in a radiation of South American silverside fishes revealed by mitochondrial and genomic RAD data

Lily C. Hughes , Yamila P. Cardoso, Julie A. Sommer, Roberto Cifuentes, Mariela Cuello, Gustavo M. Somoza, Mariano González‐Castro, Luiz R. Malabarba, Victor Cussac, Evelyn M. Habit, Ricardo Betancur‐R & Guillermo Ortí

Abstract

Rivers and lake systems in the southern cone of South America have been widely influenced by historical glaciations, carrying important implications for the evolution of aquatic organisms, including prompting transitions between marine and freshwater habitats and by triggering hybridization among incipient species via waterway connectivity and stream capture events. Silverside fishes (Odontesthes) in the region comprise a radiation of 19 marine and freshwater species that have been hypothesized on the basis of morphological or mitochondrial DNA data to have either transitioned repeatedly into continental waters from the sea or colonized marine habitats following freshwater diversification. New double digest restriction‐site associated DNA data presented here provide a robust framework to investigate the biogeographical history of and habitat transitions in Odontesthes. We show that Odontesthes silversides originally diversified in the Pacific but independently colonized the Atlantic three times, producing three independent marine‐to‐freshwater transitions. Our results also indicate recent introgression of marine mitochondrial haplotypes into two freshwater clades, with more recurring instances of hybridization among Atlantic‐ versus Pacific‐slope species. In Pacific freshwater drainages, hybridization with a marine species appears to be geographically isolated and may be related to glaciation events. Substantial structural differences of estuarine gradients between these two geographical areas may have influenced the frequency, intensity and evolutionary effects of hybridization events.

https://onlinelibrary.wiley.com/doi/full/10.1111/mec.15350

(a) Marine and freshwater areas currently occupied by species of Odontesthes in southern South America, and photograph of Odontesthes perugiae by Y. P. Cardoso. (b) Sampling localities for ddRAD‐sequenced samples (see Appendix S1: Table S2 for description of population codes). (c) 2006 Morphological phylogenetic hypothesis for all Odontesthes species (Dyer, 2006), although lacking the newly described O. yacuman (Wingert, Ferrer, & Malabarba, 2017). Marine lineages are shown with grey branches. Shapes with black outlines indicate that cytb or ddRAD data were collected for this study for that species. (d) Maximum likelihood molecular hypothesis based on seven nuclear genes and cytb (Campanella et al., 2015), including three outgroups that inhabit the northern Pacific Ocean that are not otherwise included in this study. Branch lengths for molecular hypotheses are shown in substitutions per site, and grey branches indicate marine lineages. Species included in this study have black outlines around their shapes