Inferring Diversity and Evolution in Fish by Means of Integrative Molecular Cytogenetics

Abstract

Fish constitute a paraphyletic and profusely diversified group that has historically puzzled ichthyologists. Hard efforts are necessary to better understand this group, due to its extensive diversity. New species are often identified and it leads to questions about their phylogenetic aspects. Cytogenetics is becoming an important biodiversity-detection tool also used to measure biodiversity evolutionary aspects. Molecular cytogenetics by fluorescence in situ hybridization (FISH) allowed integrating quantitative and qualitative data from DNA sequences and their physical location in chromosomes and genomes. Although there is no intention on presenting a broader review, the current study presents some evidences on the need of integrating molecular cytogenetic data to other evolutionary biology tools to more precisely infer cryptic species detection, population structuring in marine environments, intra- and interspecific karyoevolutionary aspects of freshwater groups, evolutionary dynamics of marine fish chromosomes, and the origin and differentiation of sexual and B chromosomes. The new cytogenetic field, called cytogenomics, is spreading due to its capacity to give resolute answers to countless questions that cannot be answered by traditional methodologies. Indeed, the association between chromosomal markers and DNA sequencing as well as between biological diversity analysis methodologies and phylogenetics triggers the will to search for answers about fish evolutionary, taxonomic, and structural features.

Co-located 18S/5S rDNA arrays: an ancient and unusual chromosomal trait in Julidini species (Labridae, Perciformes)

“…In fact, although the non-syntenic organization of these rDNA classes might be interpreted as a functional advantage (Martins and Galetti 2001), the persistent 18S/5S rDNA arrays in Thalassoma and Halichoeres indicates that they are feasible and, in this case, suggesting a probable adaptive condition for this multigene organization. In addition, syntenic rDNA genes may exhibit adjacent or interspersed arrangements (Artoni et al 2015). In Julidini, hybridization signals are apparently superimposed, suggesting the occurrence of the latter kind of organization.…”

“…Different classes of repetitive DNAs are linked to chromosome rearrangements in many fish groups (Kidwell 2002, Cioffi and Bertollo 2012, Getlekha et al 2016). Indeed, repetitive DNAs may clarify the occurrence of particular chromosome rearrangements and evolutionary relationships among different taxa (Shapiro and Sternberg 2005, Biémont and Vieira 2006, Artoni et al 2015). However, the chromosome organization and the evolutionary dynamics of this important fraction of the genome are still poorly understood in Labridae fishes.…”

Evolution of trans-Andean endemic fishes of the genus Cheirodon (Teleostei: Characidae) are associated with chromosomal rearrangements

“…Due to the difficulties in sampling as well as their small size making difficult to obtain chromosomes, there is no cytogenetic information about the Cheirodon except the 2n and karyotypes of the Cheirodontinae genera Odontostilbe and Serrapinnus only [22,25,30]. These data may be used to generate cytotaxonomic information and detect evolutionary relationships to better understand the diversity of the genus Cheirodon [2]. Accordingly, in order to infer the taxonomy and evolution of the trans-Andean Characidae, in the present work we elucidated the conventional and molecular cytogenetic characteristics of its five species and contrast them with available morphological, molecular and cytogenetic data for the group.…”

Interregional cytogenetic comparisons in Halichoeres and Thalassoma wrasses (Labridae) of coastal and insular regions of the southwestern Atlantic

“…Comparative cytogenetic analyses between geographic samples of T. noronhanum (island-island), H. poeyi (coast-coast) and H. radiatus (island-island) are a first systematic assessment on the use of chromosome markers in identifying interpopulational variation in marine reef fishes. The delimitation of populations in the marine environments is largely dependent on indirect evidence and, in this respect, genetic and cytogenetic markers are very informative (Galetti et al, 2006;Artoni et al, 2015).…”

“…Cytogenetic studies in marine fish populations have been largely improved by in situ hybridization techniques (Accioly et al, 2012;Artoni et al, 2015). Indeed, the distribution and frequency of a large number of chromosomal markers have allowed the discrimination of cryptic karyotypes or slight interspecific chromosomal differentiations, not diagnosed by conventional cytogenetic techniques (Motta-Neto et al, 2011;Lima-Filho et al, 2012).…”