High Genetic Diversity despite Conserved Karyotype Organization in the Giant Trahiras from Genus Hoplias (Characiformes, Erythrinidae)

Abstract

In the fish genus Hoplias, two major general groups can be found, one of which is formed by the “common trahiras” (Hoplias malabaricus group) and the other by the “giant trahiras” (Hoplias lacerdae group, in addition to Hoplias aimara), which usually comprises specimens of larger body size. Previous investigations from the giant trahiras group recovered 2n = 50 meta/submetacentric chromosomes and no sex chromosome differentiation, indicating a probable conservative pattern for their karyotype organization. Here, we conducted comparative cytogenetic studies in six giant trahiras species, two of them for the first time. We employed standard and advanced molecular cytogenetics procedures, including comparative genomic hybridization (CGH), as well as genomic assessments of diversity levels and phylogenetic relationships among them. The results strongly suggest that the giant trahiras have a particular and differentiated evolutionary pathway inside the Hoplias genus. While these species share the same 2n and karyotypes, their congeneric species of the H. malabaricus group show a notable chromosomal diversity in number, morphology, and sex chromosome systems. However, at the same time, significant changes were characterized at their inner chromosomal level, as well as in their genetic diversity, highlighting their current relationships resulting from different evolutionary histories.

Comparison of Karyotypes in Two Hybridizing Passerine Species: Conserved Chromosomal Structure but Divergence in Centromeric Repeats

“…In addition, many macrochromosomes and microchromosomes displayed higher conspecific signals in the CGH experiment, suggesting that the two species have diverged in their centromeric repeat sequences. Our observation is consistent with other studies in birds ( Ellegren et al, 2012 ), as well as other taxa ( Haaf and Willard, 1997 ; Bensasson et al, 2008 ; Pertile et al, 2009 ; de Sassi et al, 2021 ; Oliveira et al, 2021 ), showing fast evolution of centromeric sequences. For example, comparison of the whole genome sequences of two closely related species of Ficedula flycatchers, which also belong to the Muscicapidae family, revealed that the centromeres were among the most differentiated regions of the genome between the species ( Ellegren et al, 2012 ).…”

The Genetic Differentiation of Pyrrhulina (Teleostei, Characiformes) Species is Likely Influenced by Both Geographical Distribution and Chromosomal Rearrangements

“…The development and improvement of large-scale genotyping-by-sequencing (GBS) procedures allowed high-resolution analysis using Single Nucleotide Polymorphisms (SNPs) for genetic diversity studies in non-model organisms ( Steane et al, 2011 ; Yang et al, 2013 ; Sánchez-Sevilla et al, 2015 ; Alkimin et al, 2018 ; Souza et al, 2019 ; Oliveira et al, 2020 ; Sassi et al, 2021 ). Combining such genomic and cytogenetic data for pairs of species/populations in which there are variations related to geographic distribution, analysis of chromosomal rearrangements, and sex chromosome systems provide a critical tool to understanding the role of these events to generate biodiversity.…”