Melanosome diversity and convergence in the evolution of iridescent avian feathers— implications for paleocolor reconstruction

Klara Nordén, Jaeike Faber, Frane Babarović, Tom Stubbs, Tara Selly, James Schiffbauer, Petra Peharec Štefanić, Gerald Mayr, Fiann Smithwick, Jakob Vinther

Research output: Contribution to journalArticle (Academic Journal)peer-review

7 Citations (Scopus)
286 Downloads (Pure)

Abstract

Some of the most varied colors in the natural world are created by iridescent nanostructures in bird feathers, formed by layers of melanin‐containing melanosomes. The morphology of melanosomes in iridescent feathers is known to vary, but the extent of this diversity, and when it evolved, is unknown. We use scanning electron microscopy to quantify the diversity of melanosome morphology in iridescent feathers from 97 extant bird species, covering 11 orders. In addition, we assess melanosome morphology in two Eocene birds, which are the stem lineages of groups that respectively exhibit hollow and flat melanosomes today. We find that iridescent feathers contain the most varied melanosome morphologies of all types of bird coloration sampled to date. Using our extended dataset, we predict iridescence in an early Eocene trogon (cf. Primotrogon) but not in the early Eocene swift Scaniacypselus, and neither exhibit the derived melanosome morphologies seen in their modern relatives. Our findings confirm that iridescence is a labile trait that has evolved convergently in several lineages extending down to paravian theropods. The dataset provides a framework to detect iridescence with more confidence in fossil taxa based on melanosome morphology.
Original languageEnglish
Pages (from-to)15-27
Number of pages13
JournalEvolution
Volume73
Issue number1
Early online date26 Nov 2018
DOIs
Publication statusPublished - Jan 2019

Keywords

  • bird coloration
  • convergent evolution
  • iridescence
  • melanin
  • paleocolor

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