Genomic dispersion of 28S rDNA during karyotypic evolution in the ant genus Myrmecia (Formicidae).

The chromosomal localization of 28S rDNA was investigated in 16 speices of the Australian ant genus Myrmecia, with 2n numbers ranging from 4 to 76, using the fluorescence in situ hybridization method and karyographic analysis. A unique phenomenon was observed: the number of chromosomes carrying 28S rDNA increases from 2 in species with low chromosome numbers to 19 in species with high chromosome numbers. This is termed rDNA dispersion. Centric fission and a reciprocal translocation that occurs in C-bands were detected as the major mechanisms involved in rDNA dispersion.