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ABSTRACT Even as numerous studies have documented that the red and yellow coloration resulting from the deposition of carotenoids serves as an honest signal of condition, the evolution of condition dependency is contentious. The resource trade‐off hypothesis proposes that condition‐dependent honest signalling relies on a trade‐off of resources between ornamental display and body maintenance. By this model, condition dependency can evolve through selection for a re‐allocation of resources to promote ornament expression. By contrast, the index hypothesis proposes that selection focuses mate choice on carotenoid coloration that is inherently condition dependent because production of such coloration is inexorably tied to vital cellular processes. These hypotheses for the origins of condition dependency make strongly contrasting and testable predictions about ornamental traits. To assess these two models, we review the mechanisms of production of carotenoids, patterns of condition dependency involving different classes of carotenoids, and patterns of behavioural responses to carotenoid coloration. We review evidence that traits can be condition dependent without the influence of sexual selection and that novel traits can show condition‐dependent expression as soon as they appear in a population, without the possibility of sexual selection. We conclude by highlighting new opportunities for studying condition‐dependent signalling made possible by genetic manipulation and expression of ornamental traits in synthetic biological systems.
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This content will become publicly available on December 1, 2025
Assessing the Association Between Animal Color and Behavior: A Meta‐Analysis of Experimental Studies
ABSTRACT Color varies in pattern and degree across the tree of life. In animals, genetic variation in color is hypothesized to have pleiotropic effects on a variety of behaviors due to shared dependence on underlying biochemical pathways. Such pleiotropy can constrain the independent evolution of color and behavior. Although associations between color and behavior have been reported, this relationship has not yet been addressed across a broad taxonomic scale with a formal meta‐analysis. We used a phylogenetic meta‐analytic approach to examine the relationship between individual variation in aggressive behavior and variation in multiple colors. Seventy‐four studies met our inclusion criteria (vertebrates = 70; invertebrates = 4). After accounting for phylogeny and correcting for publication bias, there was a positive association between measures of aggression and degree or area of coloration (mean = 0.248, 95% CI = (0.044, 0.477)). Because this positive association was not restricted to melanin‐based coloration, we conclude that this pattern does not strongly support the melanin pleiotropy hypothesis. Because the association was also not affected by moderators accounting for individual condition, social rank, or age, the results do not strongly support hypotheses that condition dependence accounts for relationships between color and aggressive behavior. The badge of status hypothesis predicts that arbitrary traits can evolve to signal aggression or social dominance. We propose that this is the most parsimonious explanation for the patterns we observe. Because of the lack of evidence for condition dependence in the association between color and aggression, we further propose that the genetic covariation between traits contributes to the evolution of the badges of status.
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- Award ID(s):
- 2217558
- PAR ID:
- 10568992
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 14
- Issue:
- 12
- ISSN:
- 2045-7758
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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