Chromosomal evolution and phylogenetic considerations in cuckoos (Aves, Cuculiformes, Cuculidae)

Area of Science:

• Avian genetics
• Comparative genomics
• Evolutionary biology

Background:

• The classification of Cuckoos (Cuculiformes) has historically presented challenges.
• Previous studies using osteology, behavior, ecology, morphology, and molecular data have not fully resolved their evolutionary relationships.
• The placement of Cuculiformes relative to other avian orders remains debated.

Purpose of the Study:

• To investigate the chromosome evolution within the Cuculidae family.
• To perform the first chromosome mapping for Guira guira and Piaya cayana.
• To clarify the phylogenetic position of Cuculiformes using cytogenetic data.

Main Methods:

• Comparative chromosome painting was employed on two cuckoo species: Guira guira and Piaya cayana.
• Giemsa staining was used for chromosome analysis.
• Results were compared with existing cytogenetic data for other cuckoos and proposed sister taxa (Otidiformes, Musophagiformes, Opisthocomiformes).

Main Results:

• High chromosomal diversity was observed between Guira guira (2n=76) and Piaya cayana (2n=90).
• Guira guira showed fission and fusion events, while Piaya cayana exhibited only fissions.
• No common chromosomal rearrangements were identified between these two species.
• Cytogenetic comparisons suggest at least three distinct groups within cuckoo species.
• No evidence supports a close relationship between Cuculiformes and the proposed sister groups.

Conclusions:

• The study highlights significant chromosomal evolution and diversity within the Cuculidae family.
• The distinct chromosomal landscapes of Guira guira and Piaya cayana underscore their unique evolutionary trajectories.
• Current cytogenetic data do not support the previously proposed sister-group relationships for Cuculiformes.