The day or night schedule of their ancestors makes a difference, study finds.
Published October 25, 2022 09:00AM EDT
Lots of animals are vibrantly colored, easily spotted in their surroundings. Some bright birds and lizards use their showy hues to lure mates. But some snakes and amphibians use their colors to ward off predators. Researchers were curious how these different species evolved to send different messages with their dazzling hues.
“It was really just the observation that different animals use similar colors for radically different functions,” senior author John Wiens, a professor of ecology and evolutionary biology at the University of Arizona, tells Treehugger. “For example, a male cardinal and a Madagascar tomato frog have similar bright red coloration over most of their bodies, but the function is completely different in each species.”
Researchers studied data from 1,824 land vertebrate species, noting the function of each animal’s bright coloring. They also noted whether they and their ancestors were diurnal, meaning they are active during the day, or nocturnal, or active at night.
They found that there was no obvious link between bright colors and whether species are active primarily during the day or at night. But, when they analyzed the activity of the ancestors of these species, they noticed a pattern in the relationship.
Animals with bright colors used to attract mates were linked with ancestors that were active during the day. Those with colors used to warn predators were associated with ancestors that lived a nocturnal lifestyle.
The findings were published in the journal Evolution.
Day vs. Night Activity
Animals that are active in the daylight, like birds and most lizards, use their bright colors to attract mates. That’s the case for the animals now and for their ancestors: They are active during the day.
“For animals that use these colors as warning signals (like poison frogs and coral snakes), the story is more complicated,” Wiens says. “They generally belong to groups that are ancestrally active by night. However, in many cases, the individual species in these groups that have warning coloration are active by day. This makes sense because these warning colors actually work best during the day: a predator presumably cannot see these colors at night.”
These bright colors either communicate that they have venom or other ways to defend themselves. Or sometimes, in order to appear treacherous, they look like other species that have those defenses, a trait called mimicry.
Wiens gives the example of poison frogs from Central and South America. “Frogs are ancestrally active by night. But poison frogs are a more recent group within frogs that have switched to being active by day,” he says. “And among the hundreds of species of poison frogs, they have evolved a whole rainbow of these warning colors.”
The Impact of Evolution
Early on in their history, most of the species the researchers analyzed were drably colored. But as they evolved, many of them developed vivid colors to help them reproduce and survive. Those colors were passed on to subsequent generations.
“One of the things that evolutionary biology helps tell us is how the world got to be the way that it is today,” Wiens says. “This research suggests that even though many species have evolved their conspicuous colors quite recently, the reasons behind that color evolved hundreds of millions of years ago. It is not enough to just study how the animals use these colors today.”