The authors declare no conflict of interest.
Theoretical morphology and development of flight feather vane asymmetry with experimental tests in parrots
Article first published online: 9 MAY 2014
© 2014 Wiley Periodicals, Inc.
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
Volume 322, Issue 4, pages 240–255, June 2014
How to Cite
2014. Theoretical morphology and development of flight feather vane asymmetry with experimental tests in parrots. J. Exp. Zool. (Mol. Dev. Evol.) 322B:240–255., .
- Issue published online: 12 MAY 2014
- Article first published online: 9 MAY 2014
- Manuscript Accepted: 15 APR 2014
- Manuscript Revised: 20 FEB 2014
- Manuscript Received: 16 DEC 2013
- NSF GRFP
- W. R. Coe Fund, Yale University
Asymmetry in flight feather vane width is a major functional innovation associated with the evolution of flight in the ancestors of birds. However, the developmental and morphological basis of feather shape is not simple, and the developmental processes involved in vane width asymmetry are poorly understood. We present a theoretical model of feather morphology and development that describes the possible ways to modify feather development and produce vane asymmetry. Our model finds that the theoretical morphospace of feather shape is redundant, and that many different combinations of parameters could be responsible for vane asymmetry in a given feather. Next, we empirically measured morphological and developmental model parameters in asymmetric and symmetric feathers from two species of parrots to identify which combinations of parameters create vane asymmetry in real feathers. We found that both longer barbs, and larger barb angles in the relatively wider trailing vane drove asymmetry in tail feathers. Developmentally, longer barbs were the result of an offset of the radial position of the new barb locus, whereas larger barb angles were produced by differential expansion of barbs as the feather unfurls from the tubular feather germ. In contrast, the helical angle of barb ridge development did not contribute to vane asymmetry and could be indicative of a constraint. This research provides the first comprehensive description of both the morphological and developmental modifications responsible for vane asymmetry within real feathers, and identifies key steps that must have occurred during the evolution of vane asymmetry. J. Exp. Zool. (Mol. Dev. Evol.) 322B: 240–255, 2014. © 2014 Wiley Periodicals, Inc.