The Colors of Desert Water Beetles--Environmental Effect Or Protective Coloration?1

Abstract

The best explanation for the preponderance of brightly colored and distinctly patterned water beetles in the desert regions of the southwestern United States and northern Mexico is that such coloration and marking is disruptive and helps conceal the beetles from predators in the desert streams and pools. The colors and patterns have undoubtedly developed as the effect of random gene mutations acted upon by natural selection. Some mutations producing lighter patterns may still be in a condition of balanced polymorphism with the original dark pattern genes. There is little evidence for environmental production of the light colors and patterns, and none for the genetic fixation of originally environmentally produced, nonadaptive modifications.