Plumage diversity without differential expression of pigmentation genes in a rapid avian radiation
Uncovering the molecular basis of reproductive traits is key to understanding species divergence. Capuchino Seedeaters ( Sporophila ), a radiation of genetically similar birds differing mainly in male reproductive plumage color, can be leveraged to study how such traits evolve. Outlier scans identified candidate pigmentation variants primarily in noncoding sequence, implying regulatory changes.…
Examining the genetic underpinnings of reproductive traits aids in comprehending species divergence. Capuchino Seedeaters, a group of birds sharing genetic similarities yet varying primarily in male reproductive plumage colors, offer a potential avenue to study the evolution of such traits. Outlier scans identified possible pigmentation variants, predominantly located in noncoding regions, suggesting regulatory changes.
Nevertheless, RNA sequencing of developing feather follicles revealed no differential expression of pigmentation genes across various plumage colors, with ASIP being downregulated specifically in crown feathers. The gene expression patterns, instead, differed depending on the body region. The most significant distinction between dimorphic sexes was the increased expression of the carotenoid-degrading gene BCO2 in males, which correlated with reduced carotenoid levels in male feathers.
A refined genome annotation revealed that 9.5% of the candidate variants were incorporated into coding and untranslated sequences, indicating that species-specific variants might be situated within transcribed regions and potentially function post-transcriptionally rather than through transcript abundance. This discovery leads to a reevaluation of the hypothesis regarding plumage divergence within this avian radiation.
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