Which change would most likely eliminate the trait of large, bright spots in male guppies?

The behavioral change for the avoidance of guppies from predators. This natural selection leads to the structural change in male guppies.

Explanation:The large bright spots on the male guppies are used to attract the females for the mating.But a predator which detect guppies by sight can easily sense them and hunt them.For their survival, the trait of large, bright spots on the male guppies was changed.This change leads to their less chances to be hunted by the predators.Hence this is a behavioral change for their survival.

When plants die fungi breaks them down