Cytogenetics Status of Four Ctenomys Species in the South of Brazil

Abstract

This report is a review of 20 years of cytogenetics studies in tuco-tucos from the south of Brazil and the implications for the evolution of these species as well as the relation of these data with the geological history of the Coastal Plain of southern Brazil. Two forms of Ctenomys torquatus, 2n = 44 and 46, are separated by a geographic barrier. Ctenomys flamarioni shows a constant karyotype (2n = 48) and presents high variability in FN due to constitutive heterochromatin variation. Ctenomys minutus presents the highest chromosomic variation among the species in the south of Brazil (2n = 42-50) with three chromosomic hybrid zones. Ctenomys lami, like C. minutus, presents a high chromosomic variation due to fusions and fissions of chromosome pairs 1 and 2. Both species present a close evolutionary relationship, including a chromosomic hybrid zone.

Karyotypic and molecular polymorphisms in Ctenomys torquatus (Rodentia: Ctenomyidae): taxonomic considerations

“…Our results partially agree with the well-defined situation of C. torquatus proposed by Freitas (2006). The two new karyotypes 2n = 40 and 2n = 42, and the allopatry of three distinct forms (2n = 40, 42 and 44) in only one locality (Alegrete) indicate that the karyotype polymorphism was higher than expected, but the ancestral diploid number (2n = 44) was broadly distributed along the species' geographic range.…”

“…The genus comprises more than 60 described species and shows substantial karyotypic variation, with diploid numbers (2n) ranging from 10 to 70, and autosome fundamental numbers (AN) from 16 to 84. Besides the wide interspecific chromosomal variation, intraspecific variability occurs in many species (Freitas 2006). For example, C. pearsoni of Uruguay displays karyotypes of 2n = 56, 64, 66 and 70 (Kiblisky et al 1977;Novello and Lessa 1986;Villar et al 2005), and C. rionegrensis, 2n = 52 and 56 ).…”

“…The most widely distributed species of Ctenomys in Brazil is C. torquatus Lichtenstein 1830, which inhabits lowlands with sandy soils in fields and gallery forests (Freitas 2006). It is distributed from central Uruguay to the central part of the Rio Grande do Sul State (RS) in Brazil (Freitas 1995).…”

Integrative lineage delimitation in rodents of the Ctenomys Corrientes group

“…These rodents have undergone enormous levels of chromosomal evolution with diploid numbers varying from 2n = 10 to 2n = 70, mainly due to Robertsonian translocations, but also heterochromatin additions/losses, pericentric inversions and/or tandem fusions had been postulated (Reig and Kiblisky 1969, Cook et al 1990, Massarini et al 1991, Freitas 2006, Novello and Villar 2006, Caraballo et al 2015. Their subterranean lifestyle has been associated to high population subdivision and low vagility which may have promoted the fixation of chromosomal novelties by genetic drift Kiblisky 1969, Ortells 1995).…”

Pequenos mamíferos não-voadores (Didelphimorphia, Rodentia) em campos litorâneos do extremo sul do Brasil

“…Gava & Freitas 2003, Freitas 2006, Fernandes et al 2007 e Calomys laucha G. Fischer (Camargo et al 2006). Aspectos como composição de assembléias, padrões de abundância e densidade, área de vida, uso do habitat e microhabitat por marsupiais e roedores em dunas costeiras permanecem pouco conhecidos.…”