Thistle-down velvet ants in the Desert Mimicry Ring and the evolution of white coloration: Müllerian mimicry, camouflage, and thermal ecology

Adaptive coloration among animals is one of the most recognizable outcomes
of natural selection. Here we investigate evolutionary drivers of white
coloration in velvet ants (Hymenoptera: Mutillidae), which has previously
been considered camouflage with the fruit of creosote bush. Our analyses
indicate instead that velvet ants evolved white coloration millions of
years before creosote bush was widespread in North America’s hot deserts.
Furthermore, velvet ants and the creosote fruit exhibit different spectral
reflectance patterns, which appear distinct to potential insectivorous
predators. While the white coloration in velvet ants likely did not evolve
as camouflage, we find that white-colored species remain cooler than their
red/orange relatives, and therefore we infer the white coloration likely
evolved in response to Neogene desertification. This study shows the
importance of cross-disciplinary investigation and the importance of
testing multiple hypotheses when investigating evolutionary drivers of
adaptive coloration.