Recurrent Amplifications and Deletions of Satellite DNA Accompanied Chromosomal Diversification in South American Tuco-tucos (Genus Ctenomys, Rodentia: Octodontidae): A Phylogenetic Approach

Abstract

We investigated the relationship between satellite copy number and chromosomal evolution in tuco-tucos (genus Ctenomys), a karyotypically diverse clade of rodents. To explore phylogenetic relationships among 23 species and 5 undescribed forms, we sequenced the complete mitochondrial cytochrome b genes of 27 specimens and incorporated 27 previously published sequences. We then used quantitative dot-blot techniques to assess changes in the copy number of the major Ctenomys satellite DNA (satDNA), named RPCS. Our analysis of the relationship between variation in copy number of RPCS and chromosomal changes employed a maximum-likelihood approach to infer the copy number of the satellite RPCS in the ancestors of each clade. We found that amplifications and deletions of RPCS were associated with extensive chromosomal rearrangements even among closely related species. In contrast, RPCS copy number stability was observed within clades characterized by chromosomal stability. This example reinforces the suspected role of amplification, deletion, and intragenomic movement of satDNA in promoting extensive chromosomal evolution.

Species groups and the evolutionary diversification of tuco-tucos, genusCtenomys(Rodentia: Ctenomyidae)

“…This supports the suggestion of D 'Elía et al (1999) and Slamovits et al (2001) that the asymmetric morph appeared more than once in the evolutionary history of Ctenomys. The uncertain position of C. maulinus, a species with the asymmetric sperm, and the lack of sequence data for C. yolandae, which has a third sperm morphology (Vitullo et al 1988), hinders the recovery of the evolutionary history of this variable trait.…”

“…Subsequently, Cook and Yates (1994) studied allozymic variation for Bolivian species, and Ortells (1995) examined the variation of karyotype G-band patterns in Argentinean species. More recently, Lessa and Cook (1998), D'Elía et al (1999), Mascheretti et al (2000), and Slamovits et al (2001) analyzed sequences of the mitochondrial cytochrome-b gene of some Argentinian, Brazilian, Bolivian, Chilean, and Uruguayan species (Table 1). Most of these arrangements were given additional support by phylogenetic reconstructions on the basis of sequences of 2 nuclear introns (Castillo et al 2005).…”

Evolution of Genome Size in Drosophila. Is the Invader's Genome Being Invaded by Transposable Elements?

“…We must therefore envisage that the amplification of other repetitive sequences in heterochromatin or euchromatin may be associated in one way or another with the TE copy number on chromosome arms. For example, in plants it is the size of repetitive blocks between genes that correlates with genome size (Chen et al 1997), and amplification and deletion of satellite DNA has been observed in many species (Csink and Henikoff 1998;Slamovits et al 2001), all phenomena which could have involved chromatin remodeling (Henikoff, Ahmad, and Malik 2001). The fact that D. simulans males have bigger genomes than females may indicate a specific increase of repeated sequences in the heterochromatin of the Y chromosome of that species.…”

Chromosomes and speciation in tuco-tuco (Ctenomys, Hystricognathi, Rodentia)

“…У этого вида описана система тревожной сигнализа-ции в ответ на проникновение хищников (Pearson, Christie, 1985;Lacey et al, 1997;Lacey, Wieczorek, 2004). Такой образ жизни ведет к сильной генетической и простран-ственной структурированности популяций тукотуко, значительной внутри и межвидовой дивергенции за счет дрейфа генов Lessa, Cook, 1998;Lessa, 2000;Slamovits et al, 2001;Mora et al, 2006).…”