Introduction The Southern Caracara, Caracara plancus , exhibits a highly derived karyotype within Falconiformes, a lineage characterized by extensive chromosomal reshuffling. Here, we investigated how repetitive DNA dynamics shape karyotype organization and contribute to chromosomal diversification in this species through an integrated cytogenomic approach. Methods We combined classical cytogenetics, fluorescence in situ hybridization (FISH), and satellitome analysis to characterize chromosome organization and repetitive DNA distribution in C. plancus . Conventional staining, C-banding, FISH mapping of satellite DNAs and 18S rDNA, and comparative analyses of repetitive sequence abundance were performed. Results Conventional staining and FISH consistently revealed a diploid number of 2n = 88, predominantly composed of acrocentric chromosomes with gradual size reduction and no clear macro–microchromosome distinction. C-banding showed centromeric heterochromatin in all chromosomes, with marked accumulation on the W chromosome. An autosomal pair of microchromosomes exhibited heterochromatin-associated size heteromorphism, observed in three males and one female, whereas one female showed a homomorphic state. Seven satellite DNA (satDNA) families were identified, representing a substantial genomic fraction and displaying variation in abundance between individuals and sexes. CplSat01–176 was distributed across the centromeric regions of all chromosomes, whereas CplSat02–172 and CplSat03–100 were amplified in the heteromorphic microchromosome pair, explaining the observed structural variation. Additionally, 18S rDNA clusters were mapped to two pairs of microchromosomes, differing from the typical single rDNA-bearing pair observed in most birds. Discussion Our findings indicate that repetitive DNA dynamics likely play an important role in shaping the karyotype of C. plancus and may contribute to chromosomal diversification in Falconiformes. These results reinforce the value of Falconiformes as a model for understanding avian genome evolution and the role of repetitive sequences in chromosome reorganization.
Bitencourt et al. (Thu,) studied this question.