BACKGROUND

The order Suliformes exhibits significant karyotype diversity, with species showing a ZZZZ/ZZW multiple-sex chromosome system, an uncommon occurrence in avians. Satellite DNAs (satDNAs), which consist of tandemly repeated sequences, often vary considerably even among closely related species, making them valuable markers for studying karyotypic evolution, particularly that of sex chromosome evolution. This study aims to characterize and investigate the potential role of these sequences in the karyotypic evolution of the group, with special attention to the sex chromosomes.

METHODS

Through characterizing satDNAs in two Suliformes species ( and ) using BGISEQ-500 platform and bioinformatics analysis. Their chromosomal distribution was mapped by fluorescence in situ hybridization (FISH) within their own karyotypes and in three additional Suliformes species (. , . , and ).

RESULTS

Five satDNAs were identified in and eight in . . Within the genus , three species shared specific satDNA sequences, although with different hybridization patterns. In contrast, the satDNAs of were species-specific. Additionally, the Z chromosome, including Z in species, showed reduced accumulation of repetitive DNAs.

CONCLUSIONS

These results suggest that differential accumulation of repetitive sequences may have contributed to the diversification of karyotypes in this group, particularly influencing the structure and differentiation of sex chromosomes.