In a separate study, 68 rock pocket mice were collected from four different, widely separated areas of dark lava rock. One collecting site was in Sonora, Mexico. The other three were in Chihuahua, Mexico. Dr. Nachman and colleagues observed no significant differences in the color of the rocks in the four locations sampled. However, the dark-colored mice from the three Chihuahua locations were slightly darker than the dark-colored mice from the Sonora population. The entire Mc1r gene was sequenced in all 68 of the mice collected. The mutations responsible for the dark fur color in the Sonora mice were absent from the three different populations of Chihuahua mice. No Mc1r mutations were associated with dark fur color in the Chihuahua populations. These findings suggest that adaptive dark coloration has occurred at least twice in the rock pocket mouse and that these similar phenotypic changes have different genetic bases.

Complete question:

In a separate study, 68 rock pocket mice were collected from four different, widely separated areas of dark lava rock. One collecting site was in Sonora, Mexico. The other three were in Chihuahua, Mexico. Dr. Nachman and colleagues observed no significant differences in the color of the rocks in the four locations sampled. However, the dark-colored mice from the three Chihuahua locations were slightly darker than the dark-colored mice from the Sonora population. The entire Mc1r gene was sequenced in all 68 of the mice collected. The mutations responsible for the dark fur color in the Sonora mice were absent from the three different populations of Chihuahua mice. No Mc1r mutations were associated with dark fur color in the Chihuahua populations. These findings suggest that adaptive dark coloration has occurred at least twice in the rock pocket mouse and that these similar phenotypic changes have different genetic bases.

How does this study support the  concept that natural selection is not random?  

The study supports the  concept that natural selection is not random because in different areas with the same or very similar environmental characteristics, the same phenotype was produced by different types of mutations.  

Explanation:

All of the sampled animals are inhabiting dark substrate. Probably animals needed to camouflage to survive. Natural selection must have driven them to produce dark color, similar to the substrate color. So animals from the different regions suffered different mutations that drove them to have almost the same dark fur color. The environmental condition is favoring the same phenotype.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".