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Nordén KK, Eliason CM, Stoddard MC. Evolution of brilliant iridescent feather nanostructures. eLife 2021; 10:e71179. [PMID: 34930526 PMCID: PMC8691833 DOI: 10.7554/elife.71179] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 11/19/2021] [Indexed: 12/19/2022] Open
Abstract
The brilliant iridescent plumage of birds creates some of the most stunning color displays known in the natural world. Iridescent plumage colors are produced by nanostructures in feathers and have evolved in diverse birds. The building blocks of these structures-melanosomes (melanin-filled organelles)-come in a variety of forms, yet how these different forms contribute to color production across birds remains unclear. Here, we leverage evolutionary analyses, optical simulations, and reflectance spectrophotometry to uncover general principles that govern the production of brilliant iridescence. We find that a key feature that unites all melanosome forms in brilliant iridescent structures is thin melanin layers. Birds have achieved this in multiple ways: by decreasing the size of the melanosome directly, by hollowing out the interior, or by flattening the melanosome into a platelet. The evolution of thin melanin layers unlocks color-producing possibilities, more than doubling the range of colors that can be produced with a thick melanin layer and simultaneously increasing brightness. We discuss the implications of these findings for the evolution of iridescent structures in birds and propose two evolutionary paths to brilliant iridescence.
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Affiliation(s)
- Klara Katarina Nordén
- Department of Ecology and Evolutionary Biology, Princeton UniversityPrincetonUnited States
| | - Chad M Eliason
- Grainger Bioinformatics Center, Field Museum of Natural HistoryChicagoUnited States
| | - Mary Caswell Stoddard
- Department of Ecology and Evolutionary Biology, Princeton UniversityPrincetonUnited States
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Price-Waldman R, Stoddard MC. Avian Coloration Genetics: Recent Advances and Emerging Questions. J Hered 2021; 112:395-416. [PMID: 34002228 DOI: 10.1093/jhered/esab015] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 03/22/2021] [Indexed: 11/13/2022] Open
Abstract
The colorful phenotypes of birds have long provided rich source material for evolutionary biologists. Avian plumage, beaks, skin, and eggs-which exhibit a stunning range of cryptic and conspicuous forms-inspired early work on adaptive coloration. More recently, avian color has fueled discoveries on the physiological, developmental, and-increasingly-genetic mechanisms responsible for phenotypic variation. The relative ease with which avian color traits can be quantified has made birds an attractive system for uncovering links between phenotype and genotype. Accordingly, the field of avian coloration genetics is burgeoning. In this review, we highlight recent advances and emerging questions associated with the genetic underpinnings of bird color. We start by describing breakthroughs related to 2 pigment classes: carotenoids that produce red, yellow, and orange in most birds and psittacofulvins that produce similar colors in parrots. We then discuss structural colors, which are produced by the interaction of light with nanoscale materials and greatly extend the plumage palette. Structural color genetics remain understudied-but this paradigm is changing. We next explore how colors that arise from interactions among pigmentary and structural mechanisms may be controlled by genes that are co-expressed or co-regulated. We also identify opportunities to investigate genes mediating within-feather micropatterning and the coloration of bare parts and eggs. We conclude by spotlighting 2 research areas-mechanistic links between color vision and color production, and speciation-that have been invigorated by genetic insights, a trend likely to continue as new genomic approaches are applied to non-model species.
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McCoy DE, Shultz AJ, Vidoudez C, van der Heide E, Dall JE, Trauger SA, Haig D. Microstructures amplify carotenoid plumage signals in tanagers. Sci Rep 2021; 11:8582. [PMID: 33883641 PMCID: PMC8060279 DOI: 10.1038/s41598-021-88106-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 04/08/2021] [Indexed: 02/02/2023] Open
Abstract
Brilliantly-colored birds are a model system for research into evolution and sexual selection. Red, orange, and yellow carotenoid-colored plumages have been considered honest signals of condition; however, sex differences in feather pigments and microstructures are not well understood. Here, we show that microstructures, rather than carotenoid pigments, seem to be a major driver of male-female color differences in the social, sexually-dimorphic tanager genus Ramphocelus. We comprehensively quantified feather (i) color (using spectrophotometry), (ii) pigments (using liquid chromatography-mass spectrometry (LC-MS)), and (iii) microstructures (using scanning electron microscopy (SEM) and finite-difference time-domain (FDTD) optical modeling). Males have significantly more saturated color patches than females. However, our exploratory analysis of pigments suggested that males and females have concordant carotenoid pigment profiles across all species (MCMCglmm model, female:male ratio = 0.95). Male, but not female, feathers have elaborate microstructures which amplify color appearance. Oblong, expanded feather barbs in males enhance color saturation (for the same amount of pigment) by increasing the transmission of optical power through the feather. Dihedral barbules (vertically-angled, strap-shaped barbules) in males reduce total reflectance to generate "super black" and "velvet red" plumage. Melanin in females explains some, but not all, of the male-female plumage differences. Our results suggest that a widely cited index of honesty, carotenoid pigments, cannot fully explain male appearance. We propose that males are selected to evolve amplifiers-in this case, microstructures that enhance appearance-that are not necessarily themselves linked to quality.
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Affiliation(s)
- Dakota E McCoy
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
| | - Allison J Shultz
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
- Informatics Group, Harvard University, 38 Oxford Street, Cambridge, MA, 02138, USA
- Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
- Ornithology Department, Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, CA, 90007, USA
| | - Charles Vidoudez
- Harvard Center for Mass Spectrometry, Harvard University, 52 Oxford Street (B2), Cambridge, MA, 02138, USA
| | - Emma van der Heide
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Jacqueline E Dall
- Ornithology Department, Natural History Museum of Los Angeles County, 900 Exposition Blvd, Los Angeles, CA, 90007, USA
| | - Sunia A Trauger
- Harvard Center for Mass Spectrometry, Harvard University, 52 Oxford Street (B2), Cambridge, MA, 02138, USA
| | - David Haig
- Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
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Rosetta G, An T, Zhao Q, Baumberg JJ, Tomes JJ, Gunn MD, Finlayson CE. Chromaticity of structural color in polymer thin film photonic crystals. OPTICS EXPRESS 2020; 28:36219-36228. [PMID: 33379721 DOI: 10.1364/oe.410338] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 10/18/2020] [Indexed: 06/12/2023]
Abstract
A three-dimensional goniometric study of thin-film polymer photonic crystals investigates how the chromaticity of structural color is correlated to structural ordering. Characterization of chromaticity and the angular properties of structural color are presented in terms of CIE 1931 color spaces. We examine the viewing angle dependency of the Bragg scattering cone relative to sample symmetry planes, and our results demonstrate how increased ordering influences angular scattering width and anisotropy. Understanding how the properties of structural color can be quantified and manipulated has significant implications for the manufacture of functional photonic crystals in sensors, smart fabrics, coatings, and other optical device applications.
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McCoy DE, Prum RO. Convergent evolution of super black plumage near bright color in 15 bird families. ACTA ACUST UNITED AC 2019; 222:222/18/jeb208140. [PMID: 31558610 DOI: 10.1242/jeb.208140] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 08/15/2019] [Indexed: 11/20/2022]
Abstract
We examined extremely low-reflectance, velvety black plumage patches in 32 bird species from 15 families and five orders and compared them with 22 closely related control species with normal black plumage. We used scanning electron microscopy to investigate microscopic feather anatomy, and applied spectrophotometry and hyperspectral imaging to measure plumage reflectance. Super black plumages are significantly darker and have more broadband low reflectance than normal black plumages, and they have evolved convergently in 15 avian families. Super black feather barbules quantitatively differ in microstructure from normal black feathers. Microstructural variation is significantly correlated with reflectance: tightly packed, strap-shaped barbules have lower reflectance. We assigned these super black feathers to five heuristic classes of microstructure, each of which has evolved multiple times independently. All classes have minimal exposed horizontal surface area and 3D micrometer-scale cavities greater in width and depth than wavelengths of light. In many species, barbule morphology varied between the super black exposed tip of a feather and its (i) concealed base or (ii) iridescently colored spot. We propose that super black plumages reduce reflectance, and flatten reflectance spectra, through multiple light scattering between the vertically oriented surfaces of microscale cavities, contributing to near-complete absorption of light by melanin. All super black plumage patches identified occur adjacent to brilliant colored patches. Super black plumage lacks all white specular reflections (reference points used to calibrate color perception), thus exaggerating the perceived brightness of nearby colors. We hypothesize that this sensory bias is an unavoidable by-product of color correction in variable light environments.
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Affiliation(s)
- Dakota E McCoy
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Richard O Prum
- Department of Ecology and Evolutionary Biology, and Peabody Museum of Natural History, Yale University, New Haven, CT 06520, USA
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Laczi M, Hegyi G, Kötél D, Csizmadia T, Lőw P, Török J. Reflectance in relation to macro- and nanostructure in the crown feathers of the great tit (Parus major). Biol J Linn Soc Lond 2019. [DOI: 10.1093/biolinnean/blz016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Miklós Laczi
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Budapest, Hungary
- The Barn Owl Foundation, Orosztony, Hungary
| | - Gergely Hegyi
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Budapest, Hungary
| | - Dóra Kötél
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Budapest, Hungary
| | - Tamás Csizmadia
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Péter Lőw
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - János Török
- Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Budapest, Hungary
- Ecology Research Group of the Hungarian Academy of Sciences, Budapest, Hungary
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Simpson RK, McGraw KJ. It's not just what you have, but how you use it: solar-positional and behavioural effects on hummingbird colour appearance during courtship. Ecol Lett 2018; 21:1413-1422. [DOI: 10.1111/ele.13125] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 06/06/2018] [Accepted: 06/19/2018] [Indexed: 11/29/2022]
Affiliation(s)
- Richard K. Simpson
- School of Life Sciences; Arizona State University; Tempe AZ 85287-4501 USA
| | - Kevin J. McGraw
- School of Life Sciences; Arizona State University; Tempe AZ 85287-4501 USA
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McCoy DE, Feo T, Harvey TA, Prum RO. Structural absorption by barbule microstructures of super black bird of paradise feathers. Nat Commun 2018; 9:1. [PMID: 29317637 PMCID: PMC5760687 DOI: 10.1038/s41467-017-02088-w] [Citation(s) in RCA: 3762] [Impact Index Per Article: 627.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 11/03/2017] [Indexed: 11/09/2022] Open
Abstract
Many studies have shown how pigments and internal nanostructures generate color in nature. External surface structures can also influence appearance, such as by causing multiple scattering of light (structural absorption) to produce a velvety, super black appearance. Here we show that feathers from five species of birds of paradise (Aves: Paradisaeidae) structurally absorb incident light to produce extremely low-reflectance, super black plumages. Directional reflectance of these feathers (0.05-0.31%) approaches that of man-made ultra-absorbent materials. SEM, nano-CT, and ray-tracing simulations show that super black feathers have titled arrays of highly modified barbules, which cause more multiple scattering, resulting in more structural absorption, than normal black feathers. Super black feathers have an extreme directional reflectance bias and appear darkest when viewed from the distal direction. We hypothesize that structurally absorbing, super black plumage evolved through sensory bias to enhance the perceived brilliance of adjacent color patches during courtship display.
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Affiliation(s)
- Dakota E McCoy
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
| | - Teresa Feo
- Department of Vertebrate Zoology, MRC-116, National Museum of Natural History, Smithsonian Institution, Washington, DC, 20013, USA
| | - Todd Alan Harvey
- Department of Ecology and Evolutionary Biology, and Peabody Museum of Natural History, Yale University, New Haven, CT, 06520, USA
| | - Richard O Prum
- Department of Ecology and Evolutionary Biology, and Peabody Museum of Natural History, Yale University, New Haven, CT, 06520, USA
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The influence of iridescent coloration directionality on male tree swallows’ reproductive success at different breeding densities. Behav Ecol Sociobiol 2016. [DOI: 10.1007/s00265-016-2164-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Medina JM, Díaz JA, Vukusic P. Classification of peacock feather reflectance using principal component analysis similarity factors from multispectral imaging data. OPTICS EXPRESS 2015; 23:10198-212. [PMID: 25969062 DOI: 10.1364/oe.23.010198] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Iridescent structural colors in biology exhibit sophisticated spatially-varying reflectance properties that depend on both the illumination and viewing angles. The classification of such spectral and spatial information in iridescent structurally colored surfaces is important to elucidate the functional role of irregularity and to improve understanding of color pattern formation at different length scales. In this study, we propose a non-invasive method for the spectral classification of spatial reflectance patterns at the micron scale based on the multispectral imaging technique and the principal component analysis similarity factor (PCASF). We demonstrate the effectiveness of this approach and its component methods by detailing its use in the study of the angle-dependent reflectance properties of Pavo cristatus (the common peacock) feathers, a species of peafowl very well known to exhibit bright and saturated iridescent colors. We show that multispectral reflectance imaging and PCASF approaches can be used as effective tools for spectral recognition of iridescent patterns in the visible spectrum and provide meaningful information for spectral classification of the irregularity of the microstructure in iridescent plumage.
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