A cytogenetic analysis with chromosome painting in typical antbirds (Passeriformes, Thamnophilidae) and an inference on chromosome evolution in Passeriformes.

The typical antbirds (Passeriformes, Thamnophilidae) are a monophyletic group comprising 225 species in 45 genera, primarily distributed in the lowland forests of the Neotropics. There is limited karyotypic information for this bird family, including chromosome morphology and diploid number (2n), highlighting the importance of understanding the evolutionary history of karyotypic diversification of this family. Few species in Thamnophilidae have been karyotyped to date, with observed diploid numbers ranging from 76 to 82 chromosomes. This study examined the karyotype of three Thamnophilidae species using chromosome painting: Phlegopsis nigromaculata, Thamnophilus aethiops, and Pyriglena leuconota. Whole chromosome probes from Burhinus oedicnemus (BOE) and Gallus gallus (GGA) were used, and results were compared with existing data. Additionally, three more species (Myrmotherula longipennis, Myrmoborus myotherinus, and Thamnomanes caesius) were analyzed using G-banding and/or Giemsa staining. All karyotypes aligned with the standard Aves and Passeriformes karyotype, displaying high diploid numbers (2n = 80 in Pyriglena leuconota, 2n = 82 in Thamnophilus aethiops, and 2n = 86 in Phlegopsis nigromaculata), few macrochromosomes, and numerous microchromosome pairs. Furthermore, our analysis with GGA probes in Thamnophilidae species corroborates the data observed in other Passeriformes families, indicating that the centric fission of GGA2 is a characteristic of Suboscines. Based on this result, we propose an ancestral karyotype for Suboscines that features the fission of GGA-2, which may offer a more robust explanation for the karyotypic diversity found among birds of the order Passeriformes.