How Stress Affects the Colors of Poison Frogs

Jenn Hoskins
13th April, 2024

How Stress Affects the Colors of Poison Frogs

Image Source: Suki Lee (photographer)

Key Findings

  • In South American poison frogs, researchers found genes linked to their bright warning colors
  • These genes are evolving under positive selection, suggesting they help frogs survive by deterring predators
  • The study provides insight into how these colors may also influence mate choice and species recognition
In the vibrant rainforests of South America, the genus Ranitomeya stands out with its array of brightly colored poison frogs. These frogs are not just a visual spectacle; their vivid hues serve as a warning signal, a phenomenon known as aposematism. Aposematic organisms, like these poison frogs, use their conspicuous coloration to alert predators of their toxicity and unpalatability, thereby deterring attacks and increasing their chances of survival. The study conducted by researchers at East Carolina University[1] has shed new light on the genetic mechanisms that drive this critical survival strategy. While previous research has documented the genes associated with coloration in animals, such as fish[2] and amphibians[3], and the role of these genes in survival and mating, the East Carolina University study delves into the specific genetic variations that enable these frogs to develop and maintain their warning colors. The researchers focused on nine different color morphs across four species within the Ranitomeya genus. By analyzing the transcriptomes—or the full range of messenger RNA molecules expressed by an organism—from these frogs, the team was able to pinpoint protein-coding genes that not only contribute to their coloration but are also under strong positive selection. Positive selection here refers to the process by which beneficial genetic traits become more common in a population over time because they confer some survival or reproductive advantage. Among the genes identified were those involved in melanin synthesis (dct, tyrp1, irf4), which affects pigmentation; iridophore development (fhl1), which relates to the production of reflective and iridescent colors; keratin metabolism (ovol1), which influences skin structure; pteridine synthesis (prps1, xdh), which can impact coloration; and carotenoid metabolism (adh1b, aldh2), which is tied to the production of red, orange, and yellow hues. The identification of these genes supports the idea that they may be partly responsible for the evolution of the frogs' coloration. This discovery is particularly intriguing when considered alongside previous findings. For instance, the role of carotenoids in fish coloration[2] is echoed in the frogs' carotenoid metabolism genes, suggesting shared pathways across different species. Similarly, the comprehensive cross-species list of pigmentation genes[4] provides a backdrop to this study, offering a broader context for understanding how these genes interact and evolve. Moreover, the study's findings align with the concept that aposematic signaling is not as straightforward as once thought[5]. The genetic diversity observed in the Ranitomeya frogs suggests that a variety of factors, including predator behavior and other environmental pressures, may influence the evolution of their warning colors. This complexity is further underscored by the variation within the same species, challenging the idea of uniform warning signals. The research from East Carolina University not only contributes to our understanding of the genetic basis of aposematism in Ranitomeya poison frogs but also provides a framework for future studies. By identifying genes under positive selection, scientists can explore how these genes interact with environmental factors and predator-prey dynamics to drive the evolution of warning coloration. This, in turn, can lead to broader insights into the genetic underpinnings of survival traits across a wide range of aposematic species. In conclusion, the vibrant colors of Ranitomeya poison frogs are more than just a feast for the eyes; they are a testament to the intricate dance of genetics and evolution. The study by East Carolina University not only advances our understanding of these mechanisms in poison frogs but also sets the stage for future research into the colorful world of aposematic organisms.

GeneticsAnimal ScienceEvolution

References

Main Study

1) Under pressure: evidence for selection on color-related genes in poison frogs of the genus Ranitomeya

Published 12th April, 2024

https://doi.org/10.1007/s10682-024-10297-1

Related Studies

2) Comparative transcriptomics reveals candidate carotenoid color genes in an East African cichlid fish.

https://doi.org/10.1186/s12864-020-6473-8

3) Functional colour genes and signals of selection in colour-polymorphic salamanders.

https://doi.org/10.1111/mec.15411

4) A curated gene list for expanding the horizons of pigmentation biology.

https://doi.org/10.1111/pcmr.12743

5) Diversity in warning coloration: selective paradox or the norm?

https://doi.org/10.1111/brv.12460


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