Nature 393, 68–72 (1998).

In this Letter, the maternal species listed for hybrid BE-1 is attributed to Macropus eugenii. However, our ongoing studies show that the maternal complement of chromosomes in BE-1 was inherited from a Macropus rufogriseus female. The centromeres of M. rufogriseus chromosomes are extended in comparison to all other macropod species. The extent, therefore, to which the centromere extensions shown in Fig. 4 can be attributed to hybrid-specific amplification of the retrolement KERV-1 cannot be precisely determined. Nevertheless, Southern analysis confirms that this retroelement is present at a 20% higher copy number in the hybrid's genome compared with that of its parents, and FISH analysis shows KERV-1 localization only to centromeres in the hybrid. Our conclusions regarding hybrid-specific undermethylation in this hybrid individual are not affected because M. rufogriseus shows methylation levels typical of species within the macropod group. Hybrid-specific undermethylation and genome rearrangement also remain true for the Petrogale hybrids we presented.