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Romero-Diaz C, Silva PA, Soares MC, Cardoso GC, Trigo S. Oestradiol reduces female bill colour in a mutually ornamented bird. Proc Biol Sci 2022; 289:20221677. [PMID: 36476006 PMCID: PMC9554724 DOI: 10.1098/rspb.2022.1677] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 09/20/2022] [Indexed: 12/14/2022] Open
Abstract
Carotenoid-based colour signals can be costly to produce and maintain, and trade-offs between signalling and other fitness traits are expected. In mutually ornamented species, trade-offs with reproduction may be stronger for females than males, because females often dedicate more resources to offspring production, which may lead to plastic investment in colour signals and plastic sexual dichromatism. Oestradiol is a candidate mediator of this trade-off because it regulates reproductive physiology and may also influence the expression of coloration. We tested this hypothesis by giving female common waxbills (Estrilda astrild) either oestradiol (17β-oestradiol) or empty implants during the early breeding season and measured spectral reflectance of carotenoid-based bill coloration weekly for two months. Using a model of avian vision, we found that bill colour in oestradiol-implanted females became less saturated, less red in hue and brighter, compared with control females and with unimplanted males. This resulted in a change in bill sexual dichromatism from imperceptible to perceptible. Results support the hypothesis that female reproductive physiology influences investment in coloration through changes in oestradiol and show a form of female-driven plastic sexual dichromatism. Greater sensitivity of female colour to physiological and/or environmental conditions helps explain why differences in sexual dichromatism among species differing in ecology often evolve owing to changes in female rather than male phenotype.
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Affiliation(s)
- Cristina Romero-Diaz
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, InBIO Laboratório Associado, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
- BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
| | - Paulo A. Silva
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, InBIO Laboratório Associado, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
- BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
| | - Marta C. Soares
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, InBIO Laboratório Associado, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
- BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
| | - Gonçalo C. Cardoso
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, InBIO Laboratório Associado, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
- BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
| | - Sandra Trigo
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, InBIO Laboratório Associado, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
- BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão 4485-661, Portugal
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