Abstract
Introduction: Camponotus is a diverse ant genus with over 1,500 described taxa and notable ecological and chromosomal variation. Some species display polymorphism of chromosome number, such as Camponotus rufipes which has individuals with 2n=40 and 2n=39 within the same nest. This variation is thought to result from a Robertsonian fusion between two subtelocentric chromosomes, forming a large metacentric chromosome. Methods: We performed the chromosomal mapping of the telomeric motif (TTAGG)n, highly and moderately repetitive DNA isolated from the C. rufipes genome (C0t-DNA) and the microsatellites (GA)n, and (GAG)n across both C. rufipes karyotypes (2n=40 and 2n=39). Furthermore, chromosomal measurements were obtained for both karyotypes. This analysis sought to undertand the chromosomal rearrangement that gives rise to karyotypic variation and to investigate the diversity and chromosomal organization of some repetitive sequences in this species. Results: The (TTAGG)n motif was exclusively detected at the terminal regions of the chromosomes, with no interstitial signals, consistent with the pattern typically observed in Formicidae. The C0t-DNA probe revealed signals at the centromeres of all chromosomes, including the rearranged metacentric chromosome in the 2n=39 karyotype, as well as on the short arms of subtelocentric and telocentric chromosomes, coinciding with the heterochromatin distribution previously reported for C. rufipes. Microsatellite probes exhibited a general distribution throughout the euchromatic regions, including both arms of submetacentric pairs, the rearranged metacentric chromosome, and the long arm of subtelocentric/telocentric chromosomes. Chromosomal measurements suggested the involvement of the third and either the sixth or seventh subtelocentric chromosome pairs in the rearrangement. Conclusion: We explore how the distribution of repetitive sequences suggests that the 2n=39 karyotype in C. rufipes resulted from a Robertsonian fusion. We provide the first data on the diversity and organization of some repetitive sequences in C. rufipes, as well as in Formicinae, highlighting their potential contribution to understanding chromosomal evolution in ants.