Citogenômica comparativa do andorinhão-de-coleira-branca (Streptoprocne zonaris) e do andorinhão-de coleira-falha (Streptoprocne biscutata)

Abstract

Birds have compact genomes and relatively conserved karyotypes; however, variations in chromosomal organization and in the content of repetitive sequences may reflect distinct evolutionary trajectories among related lineages. In this context, the present study performed a cytogenomic characterization of Streptoprocne zonaris and Streptoprocne biscutata (Apodidae), integrating cytogenetic and cytogenomic data. Both species presented reduced diploid numbers (2n = 68 and 2n = 72, respectively). Telomeric analysis revealed contrasting patterns between the species, with autosomal telomeric expansion in S. zonaris associated with the amplification of a satDNA family, whereas in S. biscutata the intense signal was restricted to the W chromosome. No increase in genome size was observed, and both species presented ~1.36 Gb, typical of birds. The satellitome analysis identified nine satDNA families in S. zonaris and seven in S. biscutata, with marked differences in relative abundance, nucleotide composition, and divergence patterns. The shared families showed high sequence similarity, supporting the library hypothesis. Chromosomal mapping by FISH revealed a predominantly pericentromeric localization of satDNA sequences, concentrated in a few telocentric macrochromosomes. Taken together, the results indicate that variations in the content and dynamics of satellite DNAs play a relevant role in cytogenomic differentiation between closely related species, contributing to the understanding of chromosomal evolution in Apodidae.