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Down feather morphology reflects adaptation to habitat and thermal conditions across the avian phylogeny

Pap, Péter L. ; Osváth, Gergely ; Daubner, Timea ; Nord, Andreas LU and Vincze, Orsolya (2020) In Evolution 74(10). p.2365-2376
Abstract

Down feathers are the first feather types that appear in both the phylogenetic and the ontogenetic history of birds. Although it is widely acknowledged that the primary function of downy elements is insulation, little is known about the interspecific variability in the structural morphology of these feathers, and the environmental factors that have influenced their evolution. Here, we collected samples of down and afterfeathers from 156 bird species and measured key morphological characters that define the insulatory properties of the downy layer. We then tested if habitat and climatic conditions could explain the observed between-species variation in down feather structure. We show that habitat has a very strong and clearly defined... (More)

Down feathers are the first feather types that appear in both the phylogenetic and the ontogenetic history of birds. Although it is widely acknowledged that the primary function of downy elements is insulation, little is known about the interspecific variability in the structural morphology of these feathers, and the environmental factors that have influenced their evolution. Here, we collected samples of down and afterfeathers from 156 bird species and measured key morphological characters that define the insulatory properties of the downy layer. We then tested if habitat and climatic conditions could explain the observed between-species variation in down feather structure. We show that habitat has a very strong and clearly defined effect on down feather morphology. Feather size, barbule length and nodus density all decreased from terrestrial toward aquatic birds, with riparian species exhibiting intermediate characters. Wintering climate, expressed as windchill (a combined measure of the ambient temperature and wind speed) had limited effects on down morphology, colder climate only being associated with higher nodus density in dorsal down feathers. Overall, an aquatic lifestyle selects for a denser plumulaceous layer, while the effect of harsh wintering conditions on downy structures appear limited. These results provide key evidence of adaptations to habitat at the level of the downy layer, both on the scale of macro- and micro-elements of the plumage. Moreover, they reveal characters of convergent evolution in the avian plumage and mammalian fur, that match the varying needs of insulation in terrestrial and aquatic modes of life.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Afterfeather, down, functional morphology, insulation, water resistance, wind chill
in
Evolution
volume
74
issue
10
pages
12 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:85089495016
  • pmid:32748406
ISSN
0014-3820
DOI
10.1111/evo.14075
language
English
LU publication?
yes
id
fa055049-8018-41d9-9a31-429e2a6b654d
date added to LUP
2020-08-28 14:38:06
date last changed
2021-04-27 03:00:56
@article{fa055049-8018-41d9-9a31-429e2a6b654d,
  abstract     = {<p>Down feathers are the first feather types that appear in both the phylogenetic and the ontogenetic history of birds. Although it is widely acknowledged that the primary function of downy elements is insulation, little is known about the interspecific variability in the structural morphology of these feathers, and the environmental factors that have influenced their evolution. Here, we collected samples of down and afterfeathers from 156 bird species and measured key morphological characters that define the insulatory properties of the downy layer. We then tested if habitat and climatic conditions could explain the observed between-species variation in down feather structure. We show that habitat has a very strong and clearly defined effect on down feather morphology. Feather size, barbule length and nodus density all decreased from terrestrial toward aquatic birds, with riparian species exhibiting intermediate characters. Wintering climate, expressed as windchill (a combined measure of the ambient temperature and wind speed) had limited effects on down morphology, colder climate only being associated with higher nodus density in dorsal down feathers. Overall, an aquatic lifestyle selects for a denser plumulaceous layer, while the effect of harsh wintering conditions on downy structures appear limited. These results provide key evidence of adaptations to habitat at the level of the downy layer, both on the scale of macro- and micro-elements of the plumage. Moreover, they reveal characters of convergent evolution in the avian plumage and mammalian fur, that match the varying needs of insulation in terrestrial and aquatic modes of life.</p>},
  author       = {Pap, Péter L. and Osváth, Gergely and Daubner, Timea and Nord, Andreas and Vincze, Orsolya},
  issn         = {0014-3820},
  language     = {eng},
  number       = {10},
  pages        = {2365--2376},
  publisher    = {Wiley-Blackwell},
  series       = {Evolution},
  title        = {Down feather morphology reflects adaptation to habitat and thermal conditions across the avian phylogeny},
  url          = {http://dx.doi.org/10.1111/evo.14075},
  doi          = {10.1111/evo.14075},
  volume       = {74},
  year         = {2020},
}