Cytogenetic characterization and phylogenetic analysis in two Tyranninae species (Aves: Passeriformes): the leading edge of chromosome evolution in Passeriformes

Chromosome painting has proven to be an essential tool for elucidating the evolutionary mechanisms underlying avian karyotype diversification and for identifying key synapomorphies that enhance our understanding of avian phylogenetic relationships. In the Neotropical region, the family Tyrannidae exhibits the greatest species diversity, providing valuable opportunities to investigate chromosomal evolution among closely related taxa. To contribute to our understanding of chromosomal evolution within Tyrannidae, we analyzed the karyotypes of two representative species, Myiozetetes cayanensis and Lathrotriccus euleri, combining classical cytogenetic techniques with fluorescence in situ hybridization (FISH). We employed whole-chromosome probes from Gallus gallus (GGA) and Leucopternis albicollis (LAL), as well as 18S rDNA and telomeric repeats (TTAGGG)n probes. Our results revealed the conserved karyotypic structure characteristic of Passeriformes (approximately 80 chromosomes), with M. cayanensis exhibiting 2n = 80 and L. euleri 2n = 78. In both species, the karyotypes are predominantly composed of acrocentric chromosomes. Telomeric probes produced signals restricted to terminal chromosomal regions, while 18S rDNA probes hybridized to a single pair of microchromosomes. Probes from GGA and LAL revealed chromosomal fissions and inversions in both species. Similar rearrangements have been observed in other tyrannid species from the subfamilies Fluvicolinae, Tyranninae, and Elaeniinae, suggesting a possible shared evolutionary pattern within Tyrannidae.