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Natural and sexual selection act on different axes of variation in avian plumage color.

Dunn PO, Armenta JK, Whittingham LA - Sci Adv (2015)

Bottom Line: The bright colors of birds are often attributed to sexual selection on males, but in many species both sexes are colorful and it has been long debated whether sexual selection can also explain this variation.We show that most evolutionary transitions in color have been toward similar plumage in both sexes, and the color of both sexes (for example, bright or dull) was associated with indices of natural selection (for example, habitat type), whereas sexual differences in color were primarily associated with indices of sexual selection on males (for example, polygyny and large testes size).Debate about the evolution of bird coloration can be resolved by recognizing that both natural and sexual selection have been influential, but they have generally acted on two different axes: sexual selection on an axis of sexual differences and natural selection on both sexes for the type of color (for example, bright or dull).

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA.

ABSTRACT
The bright colors of birds are often attributed to sexual selection on males, but in many species both sexes are colorful and it has been long debated whether sexual selection can also explain this variation. We show that most evolutionary transitions in color have been toward similar plumage in both sexes, and the color of both sexes (for example, bright or dull) was associated with indices of natural selection (for example, habitat type), whereas sexual differences in color were primarily associated with indices of sexual selection on males (for example, polygyny and large testes size). Debate about the evolution of bird coloration can be resolved by recognizing that both natural and sexual selection have been influential, but they have generally acted on two different axes: sexual selection on an axis of sexual differences and natural selection on both sexes for the type of color (for example, bright or dull).

No MeSH data available.


Related in: MedlinePlus

Sexual dichromatism in brightness (PC1) and hue (PC2) in relation to mating system categories.Mean (squares) and SE (lines) values are based on full phylogenetic generalized least squares (PGLS) models (table S3). Note that polygynous males were duller than females because many species had extensive black plumage (fig. S3).
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Figure 2: Sexual dichromatism in brightness (PC1) and hue (PC2) in relation to mating system categories.Mean (squares) and SE (lines) values are based on full phylogenetic generalized least squares (PGLS) models (table S3). Note that polygynous males were duller than females because many species had extensive black plumage (fig. S3).

Mentions: When we examined plumage color in relation to 10 indices of sexual and natural selection, we found that similar changes in the color of both sexes (that is, toward both dull or both bright) were primarily related to indices of natural selection, whereas changes in one sex (leading to sexual dichromatism) were related to indices of both sexual and natural selection (Figs. 2 to 4 and tables S2 and S3). To examine the factors associated with color changes in both sexes, we restricted the analysis to the middle 50% of species (n = 489) in which both sexes had relatively similar plumage (that is, species in the interquartile range of sexual dichromatism). This allowed us to focus on the factors that influence changes in brightness and hue in both sexes without the potentially confounding effects of large changes in dichromatism. In these 489 monochromatic species, brighter plumage was associated with migratory behavior, breeding in the subtropics, semiprecocial young, male parental care, and open (noncavity) nests (table S2). Duller plumage in both sexes was associated with sedentary behavior, breeding in the tropics, altricial young, lack of male parental care, and cavity nesting. Note that these are general characteristics, because some of these variables rarely co-occur (for example, only 5% of species had both altricial young and no male care). Plumage with more UV/blue/green reflectance (higher PC2) in both sexes was associated with larger body mass, sedentary behavior, semiprecocial young (that is, gulls with white UV-reflecting plumage), male parental care, and nesting in trees (table S2). More red/orange reflectance (lower PC2) in the plumage was associated with smaller body mass, migratory behavior, altricial young, lack of male parental care, and nesting on the ground.


Natural and sexual selection act on different axes of variation in avian plumage color.

Dunn PO, Armenta JK, Whittingham LA - Sci Adv (2015)

Sexual dichromatism in brightness (PC1) and hue (PC2) in relation to mating system categories.Mean (squares) and SE (lines) values are based on full phylogenetic generalized least squares (PGLS) models (table S3). Note that polygynous males were duller than females because many species had extensive black plumage (fig. S3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643820&req=5

Figure 2: Sexual dichromatism in brightness (PC1) and hue (PC2) in relation to mating system categories.Mean (squares) and SE (lines) values are based on full phylogenetic generalized least squares (PGLS) models (table S3). Note that polygynous males were duller than females because many species had extensive black plumage (fig. S3).
Mentions: When we examined plumage color in relation to 10 indices of sexual and natural selection, we found that similar changes in the color of both sexes (that is, toward both dull or both bright) were primarily related to indices of natural selection, whereas changes in one sex (leading to sexual dichromatism) were related to indices of both sexual and natural selection (Figs. 2 to 4 and tables S2 and S3). To examine the factors associated with color changes in both sexes, we restricted the analysis to the middle 50% of species (n = 489) in which both sexes had relatively similar plumage (that is, species in the interquartile range of sexual dichromatism). This allowed us to focus on the factors that influence changes in brightness and hue in both sexes without the potentially confounding effects of large changes in dichromatism. In these 489 monochromatic species, brighter plumage was associated with migratory behavior, breeding in the subtropics, semiprecocial young, male parental care, and open (noncavity) nests (table S2). Duller plumage in both sexes was associated with sedentary behavior, breeding in the tropics, altricial young, lack of male parental care, and cavity nesting. Note that these are general characteristics, because some of these variables rarely co-occur (for example, only 5% of species had both altricial young and no male care). Plumage with more UV/blue/green reflectance (higher PC2) in both sexes was associated with larger body mass, sedentary behavior, semiprecocial young (that is, gulls with white UV-reflecting plumage), male parental care, and nesting in trees (table S2). More red/orange reflectance (lower PC2) in the plumage was associated with smaller body mass, migratory behavior, altricial young, lack of male parental care, and nesting on the ground.

Bottom Line: The bright colors of birds are often attributed to sexual selection on males, but in many species both sexes are colorful and it has been long debated whether sexual selection can also explain this variation.We show that most evolutionary transitions in color have been toward similar plumage in both sexes, and the color of both sexes (for example, bright or dull) was associated with indices of natural selection (for example, habitat type), whereas sexual differences in color were primarily associated with indices of sexual selection on males (for example, polygyny and large testes size).Debate about the evolution of bird coloration can be resolved by recognizing that both natural and sexual selection have been influential, but they have generally acted on two different axes: sexual selection on an axis of sexual differences and natural selection on both sexes for the type of color (for example, bright or dull).

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA.

ABSTRACT
The bright colors of birds are often attributed to sexual selection on males, but in many species both sexes are colorful and it has been long debated whether sexual selection can also explain this variation. We show that most evolutionary transitions in color have been toward similar plumage in both sexes, and the color of both sexes (for example, bright or dull) was associated with indices of natural selection (for example, habitat type), whereas sexual differences in color were primarily associated with indices of sexual selection on males (for example, polygyny and large testes size). Debate about the evolution of bird coloration can be resolved by recognizing that both natural and sexual selection have been influential, but they have generally acted on two different axes: sexual selection on an axis of sexual differences and natural selection on both sexes for the type of color (for example, bright or dull).

No MeSH data available.


Related in: MedlinePlus