Recurrent amplifications and deletions of satellite DNA accompanied chromosomal diversification in south American tuco-tucos (genus Ctenomys, Rodentia : Octodontidae): A phylogenetic approach

We investigated the relationship between satellite copy number and chromoso mal evolution in tuco-tucos (genus Ctenomys), a karyotypically diverse clad e of rodents. To explore phylogenetic relationships among 23 species and 5 undescribed forms, we sequenced the complete mitochondrial cytochrome b gen es of 27 specimens and incorporated 27 previously published sequences. We t hen used quantitative dot-blot techniques to assess changes in the copy num ber of the major Ctenomys satellite DNA (satDNA), named RPCS. Our analysis of the relationship between variation in copy number of RPCS and chromosoma l changes employed a maximum-likelihood approach to infer the copy number o f the satellite RPCS in the ancestors of each clade. We found that amplific ations and deletions of RPCS were associated with extensive chromosomal rea rrangements even among closely related species. In contrast, RPCS copy numb er stability was observed within clades characterized by chromosomal stabil ity. This example reinforces the suspected role of amplification, deletion, and intragenomic movement of satDNA in promoting extensive chromosomal evo lution.