Understanding the chromosomal evolution in cuckoos (Aves, Cuculiformes): a journey through unusual rearrangements.

The Cuculiformes are a family of over 150 species that live in a range of habitats, such as forests, savannas, and deserts. Here, bacterial artificial chromosome (BAC) probes (75 from chicken and 14 from zebra finch macrochromosomes 1-10 +ZW and for microchromosomes 11-28 (except 16)) were used to investigate chromosome homologies between chicken and the squirrel cuckoo ( Piaya cayana ). In addition, repetitive DNA probes were applied to characterize the chromosome organization and to explore the role of these sequences in the karyotype evolution of P . cayana . We also applied BAC probes for chicken chromosome 17 and Z to the guira cuckoo ( Guira guira ) to test whether this species has an unusual Robertsonian translocation between a microchromosome and the Z chromosome, recently described in the smooth-billed ani ( Crotophaga ani ). Our results revealed extensive chromosome reorganization with inter- and intrachromosomal rearrangements in P . cayana , including a conspicuous chromosome size and heterochromatin polymorphism on chromosome pair 20. Furthermore, we confirmed that the Z-autosome Robertsonian translocation found in C . ani is also found in G . guira , not P . cayana . These findings suggest that this translocation occurred prior to the divergence between C . ani and G . guira , but after the divergence with P . cayana .