Genetics: Light coloured vs dark coloured clams: Population drift: Gene Fitness

Question

Suppose your model of selection represents the change in frequency of plain white coquina clams because predatory birds see and remove them more quickly from a beach with dark-colored sand. If larval offspring from this population drift to a different beach made of light-colored sand, could selection go the other way? What does this say about fitness of a particular gene?

Answer 1

Selection could very likely change for the species if they drift to a different substrate (light-colored sand). The light-colored clams would blend in better with their new environment which makes it harder for predators to detect. In this new population, the frequency of plain white coquina clam would increase while other darker-colored variations would decrease due to predations. Thus, the fitness of a particular gene depends on the species' surroundings and may not be prevalent until, by chance, the right conditions are met.