The brown rabbits will reproduce effectively whereas the white rabbits will not survive in the events when the winter will get warmer with warmer temperature lasting longer.
Step-by-step explanation:
The theory of Darwin suggests the Survival of the Fittest. The brown rabbits due to their adaptive skin color to the warmer temperature that is summer when everything in the environment goes pale due to heat will help them survive.
Similar in context, winter brings snow and so the white rabbits will thrive in more. But when the natural pursuit of temperature or climate changes, the brown rabbit lasting longer in warmer temperature will survive more with white ones wiping out.