Hidden Diversity in the Populations of the Armored Catfish Ancistrus Kner, 1854 (Loricariidae, Hypostominae) from the Paraná River Basin Revealed by Molecular and Cytogenetic Data

Abstract

Only one species of armored catfish, Ancistrus cirrhosus Valenciennes 1836, has been historically described in the basin of the Paraná River, from Misiones (Argentina). However, the ample variation found in the morphology and coloration of the populations sampled in the tributaries of the Brazilian state of Paraná makes it difficult to establish the real taxonomic status and evolutionary history of the Ancistrus specimens, suggesting that A. cirrhosus is not the only species found in this basin. By combining data on mitochondrial DNA (COI gene) and chromosomal markers from different Ancistrus populations, totaling 144 specimens, in the tributaries of the Paraná, and specimens from Misiones (type-locality of A. cirrhosus), we detected five distinct evolutionary lineages. All the specimens were 2n = 50, but had four distinct karyotype formulae. The results of the Generalized Mixed Yule Coalescent (GYMC) and the genetic distances (uncorrected P-values) between lineages ranged from 3 to 5%. Clusters of 18S rDNA were observed in a single chromosome pair in seven populations of Ancistrus, but at different positions, in some cases, in synteny with the 5S rDNA sites. Multiple 5S sites were observed in all populations. Overall, the cytogenetic data reinforce the genetic evidence of the diversification of lineages, and indicate the existence of candidate species in the study region. The evidence indicates that at least four candidate species of the Ancistrus may coexist in the Paraná basin besides A. cirrhosus. Overall, our results provide a comprehensive scenario for the genetic variation among Ancistrus populations and reinforce the conclusion that the true diversity of the freshwater fish of the Neotropical regions has been underestimated.

Centric Fusions behind the Karyotype Evolution of Neotropical Nannostomus Pencilfishes (Characiforme, Lebiasinidae): First Insights from a Molecular Cytogenetic Perspective

“…Chromosomal mapping of rDNA clusters has repeatedly helped to unveil diverse evolutionary issues (e.g., [82,83]). Particularly in fishes, it provided valuable clues about the incidence of cryptic, morphologically indistinguishable sibling species [5,6,8,10,84], polyploidization and interspecific hybridization events [85,86], a geographical gradient of genomic and morphological change [87], patterns of sex chromosome differentiation [80,[88][89][90], and the correlation of genome dynamics in response to environmental cues [91,92]. Among the Nannostomus species investigated here, chromosomal mapping revealed somewhat uniform patterns of distribution for both rDNA classes, with one to few sites of accumulation, as found in most fishes [93,94], as well as in some other lebiasinids [21,22] investigated to date.…”

“…The Neotropical region harbors the richest freshwater ichthyofauna in the world, with approximately 5200 species belonging to 17 orders, thus representing about 40% of the freshwater biodiversity worldwide [1][2][3]. Moreover, the amount of cryptic and until now morphologically undistinguishable species suggests much higher species diversity (e.g., [4][5][6][7][8][9]). Fueled by these discoveries, the knowledge about the karyotype differentiation in Neotropical fishes has been rapidly growing (especially during the last few decades) and several important models for studying both sympatric and allopatric speciation, species complexes, and sex chromosome evolution have emerged [9][10][11].…”

Cytogenetic characterization of Hypostomus soniae Hollanda-Carvalho & Weber, 2004 from the Teles Pires River, southern Amazon basin: evidence of an early stage of an XX/XY sex chromosome system

“…A range of sex chromosome systems found in 705 fish species are available in the Tree of Sex Consortium (2014) database. Differentiated sex chromosome systems are not very common in the loricariid catfishes, although simple (Alves et al 2006; de Oliveira et al 2007; Prizon et al 2017) and multiple systems (Centofante et al 2006; de Oliveira et al 2008; Blanco et al 2014) have been described in this family. In the genus Hypostomus , only a simple sexual chromosomal system has been described, with a XX/XY system being found in H. ancistroides and H. macrops , identified as Plecostomus ancistroides and P. macrops , respectively (Michele et al 1977; Rocha-Reis et al 2018), and a ZZ/ZW system in Hypostomus sp.…”

Iterative taxonomic study of Pareiorhaphis hystrix (Siluriformes, Loricariidae) suggests a single, yet phenotypically variable, species in south Brazil

“…The geographic distribution of such variation has not been investigated, and it is thus not clear whether these represent intraspecific variation or could indicate the presence of multiple species. The combination of phenotypical data with molecular markers in an iterative approach, as opposed to the traditionally used morphology or molecules alone, has been efficient in fish population studies, and their use can contribute to the identification of cryptic species [9,10].…”