Scientists discuss the evolution of the white coloration of velvet ants

As you traverse the arid southwestern United States, you see miles and miles of creosote bushes. Well adapted to the warm and thirsty landscape, the evergreen shrub, also known as greasewood, chaparral, and governess, produces tufts of fluffy white fruit capsules. Similar fluffy white insects live among the plants, difficult to distinguish from the fruit, which are, in fact, a species of wasp known as velvet ants with thistle.

“His scientific name is Dasymutilla gloriosa and they’re one of my favorites, “says biologist Joseph Wilson of Utah State University.

Looking at the velvet ant and creosote fruit side by side, it’s easy to imagine that the fuzzy wasp’s white coloration evolved as camouflage.

Not so fast, Wilson says.

“In the animal kingdom, there are relatively few examples of white being an adaptive color outside of arctic environments,” he says. “White coloration may be aposematic, that is, coloration intended to warn or repel predators, but it may also play a role in thermoregulation.”

Wilson and his colleagues at the USU Jeni Sidwell and James Pitts, along with Matthew Forister of the University of Nevada and Kevin Williams of the California Department of Food and Agriculture, discuss new findings on the evolution of Thistle-down in the issue of 15 of July 2020 of Biology charts.

In 2015, USU biologists identified velvet ants from North America as one of the largest Mullerian mimicry complexes in the world. Mimicry, a form of defense in which one animal copies another from a different species in appearance, actions, or sound, is an evolutionary phenomenon that scientists identified in the late 1800s.^th century.

“It stands to reason that velvet thistle ants evolved their appearance to hide from predators among fallen creosote fruits,” says Wilson, an associate professor in the Department of Biology at the Tooele campus of USU. “But wasps preceded the arrival of the creosote bush in the southwestern United States by millions of years. So we investigated other explanations for its white coloration.”

The team assumed that the pale color of wasps could provide thermo-ecological benefits in their hot environment. The researchers investigated genetic data. They used reflectance spectrometry to compare the spectral reflectance of wasps and creosote fruit. Using a thermal imaging camera and other probes, the scientists measured the external and internal temperatures of the organisms.

Taking extensive data samples and following various analyzes, the team concluded that the white coloration of velvet ants is an adaptation to the warm desert environment, rather than the pressure of predation.

“We learned not to judge a book by its cover,” says Wilson. “We all look outside our narrow specializations to apply various disciplines to the questions we ask ourselves. When considering coloration, never assume that nonhumans see colors the way humans do. Velvet ants with thistle are white to us and They look like creosote fruit, but we don’t know exactly what wasp predators look like. ”