The carotenoid redshift: Physical basis and implications for visual signaling
Abstract Carotenoid pigments are the basis for much red, orange, and yellow coloration in nature and central to visual signaling. However, as pigment concentration increases, carotenoid signals not only darken and become more saturated but they also redshift; for example, orange pigments can look re...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2023-09-01
|
| Series: | Ecology and Evolution |
| Subjects: | |
| Online Access: | https://doi.org/10.1002/ece3.10408 |
| _version_ | 1797542891542806528 |
|---|---|
| author | Dakota E. McCoy Allison J. Shultz Jacqueline E. Dall Jennifer A. Dionne Sönke Johnsen |
| author_facet | Dakota E. McCoy Allison J. Shultz Jacqueline E. Dall Jennifer A. Dionne Sönke Johnsen |
| author_sort | Dakota E. McCoy |
| collection | DOAJ |
| description | Abstract Carotenoid pigments are the basis for much red, orange, and yellow coloration in nature and central to visual signaling. However, as pigment concentration increases, carotenoid signals not only darken and become more saturated but they also redshift; for example, orange pigments can look red at higher concentration. This occurs because light experiences exponential attenuation, and carotenoid‐based signals have spectrally asymmetric reflectance in the visible range. Adding pigment disproportionately affects the high‐absorbance regions of the reflectance spectra, which redshifts the perceived hue. This carotenoid redshift is substantial and perceivable by animal observers. In addition, beyond pigment concentration, anything that increases the path length of light through pigment causes this redshift (including optical nano‐ and microstructures). For example, male Ramphocelus tanagers appear redder than females, despite the same population and concentration of carotenoids, due to microstructures that enhance light–pigment interaction. This mechanism of carotenoid redshift has sensory and evolutionary consequences for honest signaling in that structures that redshift carotenoid ornaments may decrease signal honesty. More generally, nearly all colorful signals vary in hue, saturation, and brightness as light–pigment interactions change, due to spectrally asymmetrical reflectance within the visible range of the relevant species. Therefore, the three attributes of color need to be considered together in studies of honest visual signaling. |
| first_indexed | 2024-03-10T13:36:57Z |
| format | Article |
| id | doaj.art-9a0e978378494aab9b37f732a4722a97 |
| institution | Directory Open Access Journal |
| issn | 2045-7758 |
| language | English |
| last_indexed | 2024-03-10T13:36:57Z |
| publishDate | 2023-09-01 |
| publisher | Wiley |
| record_format | Article |
| series | Ecology and Evolution |
| spelling | doaj.art-9a0e978378494aab9b37f732a4722a972023-11-21T07:26:25ZengWileyEcology and Evolution2045-77582023-09-01139n/an/a10.1002/ece3.10408The carotenoid redshift: Physical basis and implications for visual signalingDakota E. McCoy0Allison J. Shultz1Jacqueline E. Dall2Jennifer A. Dionne3Sönke Johnsen4Department of Materials Science and Engineering Stanford University Stanford California USAOrnithology Department Natural History Museum of Los Angeles County Los Angeles California USAOrnithology Department Natural History Museum of Los Angeles County Los Angeles California USADepartment of Materials Science and Engineering Stanford University Stanford California USADepartment of Biology Duke University Durham North Carolina USAAbstract Carotenoid pigments are the basis for much red, orange, and yellow coloration in nature and central to visual signaling. However, as pigment concentration increases, carotenoid signals not only darken and become more saturated but they also redshift; for example, orange pigments can look red at higher concentration. This occurs because light experiences exponential attenuation, and carotenoid‐based signals have spectrally asymmetric reflectance in the visible range. Adding pigment disproportionately affects the high‐absorbance regions of the reflectance spectra, which redshifts the perceived hue. This carotenoid redshift is substantial and perceivable by animal observers. In addition, beyond pigment concentration, anything that increases the path length of light through pigment causes this redshift (including optical nano‐ and microstructures). For example, male Ramphocelus tanagers appear redder than females, despite the same population and concentration of carotenoids, due to microstructures that enhance light–pigment interaction. This mechanism of carotenoid redshift has sensory and evolutionary consequences for honest signaling in that structures that redshift carotenoid ornaments may decrease signal honesty. More generally, nearly all colorful signals vary in hue, saturation, and brightness as light–pigment interactions change, due to spectrally asymmetrical reflectance within the visible range of the relevant species. Therefore, the three attributes of color need to be considered together in studies of honest visual signaling.https://doi.org/10.1002/ece3.10408honest signalhuelight absorbanceopticspigmentsexual selection |
| spellingShingle | Dakota E. McCoy Allison J. Shultz Jacqueline E. Dall Jennifer A. Dionne Sönke Johnsen The carotenoid redshift: Physical basis and implications for visual signaling Ecology and Evolution honest signal hue light absorbance optics pigment sexual selection |
| title | The carotenoid redshift: Physical basis and implications for visual signaling |
| title_full | The carotenoid redshift: Physical basis and implications for visual signaling |
| title_fullStr | The carotenoid redshift: Physical basis and implications for visual signaling |
| title_full_unstemmed | The carotenoid redshift: Physical basis and implications for visual signaling |
| title_short | The carotenoid redshift: Physical basis and implications for visual signaling |
| title_sort | carotenoid redshift physical basis and implications for visual signaling |
| topic | honest signal hue light absorbance optics pigment sexual selection |
| url | https://doi.org/10.1002/ece3.10408 |
| work_keys_str_mv | AT dakotaemccoy thecarotenoidredshiftphysicalbasisandimplicationsforvisualsignaling AT allisonjshultz thecarotenoidredshiftphysicalbasisandimplicationsforvisualsignaling AT jacquelineedall thecarotenoidredshiftphysicalbasisandimplicationsforvisualsignaling AT jenniferadionne thecarotenoidredshiftphysicalbasisandimplicationsforvisualsignaling AT sonkejohnsen thecarotenoidredshiftphysicalbasisandimplicationsforvisualsignaling AT dakotaemccoy carotenoidredshiftphysicalbasisandimplicationsforvisualsignaling AT allisonjshultz carotenoidredshiftphysicalbasisandimplicationsforvisualsignaling AT jacquelineedall carotenoidredshiftphysicalbasisandimplicationsforvisualsignaling AT jenniferadionne carotenoidredshiftphysicalbasisandimplicationsforvisualsignaling AT sonkejohnsen carotenoidredshiftphysicalbasisandimplicationsforvisualsignaling |