Phylogeography and karyotypic evolution of some Deuterodon species from southeastern Brazil (Characiformes, Characidae, Stethaprioninae)

Abstract

Deuterodon is a genus of the subfamily Stethaprioninae, a group of Neotropical fish known as tetras. Deuterodon hastatus represents a species complex, which is supported by cytogenetic and molecular data. In this study, we show the results of comparative evolutionary analyses of the ATP synthase subunit 6 gene in four Deuterodon species, in addition to ribosomal markers ( 18S rDNA and 5S rDNA ), of a new population of the D. hastatus species complex from the Angra dos Reis/RJ region. The study population comprised a new cytotype, which we refer to as cytotype D, in D. hastatus , with 2n = 50 = 6M+8SM+8ST+28A. We obtained three different clades of D. hastatus in our phylogeny, one of them composed only by specimens of cytotype D. By using molecular clock dating, we observed that the radiation of Deuterodon from southeastern Brazil seemed to be associated with neotectonic events that occurred during the Miocene-Pliocene and Pliocene-Pleistocene transitions, marked by the capture of headwater streams and marine transgressions. The results obtained reinforce the idea that D. hastatus is a species complex, and at least three evolutionary significant units were identified in this group.

Chromosomal Radiation: A model to explain karyotypic diversity in cryptic species

“…This was reflected in a revision by Terán et al (2020 ), which involved the reassignment of some Astyanax species to six different genera, reverberating the molecular phylogenies and the chromosomal features described. For instance, Astyanax species from coastal river basins of Brazil were now assigned to the genus Deuterodon (such as D. hastatus , D. giton and D. intermedius ), which lacks the As51 satellite DNA and in which the rDNA 5S is located only on distal position on ST/A chromosomes ( Kavalco et al ., 2004 , 2009 ; Rodrigues-Oliveira et al, 2023 ). Meanwhile, traditional species complexes such as Astyanax fasciatus and Astyanax scabripinnis were moved to the genus Psalidodon , which has high levels of karyotypic diversity and chromosomal rearrangements, where the As51 satellite DNA plays an important role ( Kavalco et al ., 2013 ).…”