A recent investigation has revealed that the capacity for color vision in animals developed over 100 million years prior to the arrival of vibrant fruits and flowers. Additionally, there has been a significant increase in the use of color signals in the past 100 million years.
Colors play a crucial role in communication among various animal species. For instance, peacocks flaunt their colorful tails, which feature shimmering eyespots, to woo peahens during mating rituals. This illustrates the concept of sexual selection through color signaling. Additionally, bright colors can be found in poisonous species, such as certain venomous snakes and the vividly hued poison frogs of Central and South America, serving as alerts to potential predators.
A recent study conducted by researchers from the University of Arizona examined the evolutionary timeline of color vision in animals and the various roles of “conspicuous colors” in plants and animals. Conspicuous colors, including red, yellow, orange, blue, and purple, are those that stand out against most environments.
Utilizing statistical analysis, the researchers determined that color vision originated in animals over 100 million years before colorful fruits and flowers appeared. The study, directed by John J. Wiens, a professor in the Ecology and Evolutionary Biology department at U of A, is featured in the journal Biological Reviews.
The research distinguishes between two types of color signals used by animals—warning signals and sexual signals—while also assessing the color signals utilized by plants for their flowers and fruits.
According to Wiens, conspicuous colors in plants serve two primary purposes: for fruits, they aid in seed dispersal; for flowers, they facilitate pollen distribution.
“Our goal was to discover when bright colors evolved and their primary purposes. This was a key factor in motivating our study,” remarked Zachary Emberts, co-author of the study and an assistant professor of integrative biology at Oklahoma State University. Emberts was a postdoctoral fellow at U of A during the research.
The emergence of color vision in animals occurred approximately 500 million years ago, while colorful fruits surfaced about 350 million years ago, and colorful flowers appeared roughly 200 million years ago, as stated by Wiens.
Wiens noted that warning color signals appeared before sexual color signals, dating back to around 150 million years ago, with sexual color signals emerging about 100 million years ago.
“We’ve witnessed a remarkable increase in both warning and sexual color signals over the last 100 million years,” Wiens explained.
This phenomenon is intriguing, especially considering that color vision emerged roughly 400 million years earlier. Though the exact reasons for this explosion remain unclear, the research team identified three major groups that likely contributed to the increase in warning signals: ray-finned fishes in marine habitats, and birds and lizards on land.
Wiens emphasized that warning color signals are far more prevalent in the animal kingdom compared to sexual signals, which are restricted to arthropods and vertebrates.
“In fact, warning signals are at least five times more widespread than sexual ones. That’s the overarching trend,” Wiens pointed out.
The widespread nature of warning color signals may be due to the fact that an animal displaying these colors does not need to possess color vision itself to warn others of potential danger. Interestingly, species showcasing warning colors don’t need advanced eyesight.
In contrast, both male and female animals need to have developed vision for signaling each other through sexual color cues, which is why these signals are found only in two major animal groups: vertebrates (including fish, amphibians, mammals, birds, and reptiles) and arthropods (like insects and spiders).
“In future research, it would be fascinating to explore what influences the ability of animals to perceive specific colors such as red or blue,” Emberts concluded.
