Still another reason why variation is maintained in a population is because natural selection may favor one phenotype at one time or place and favor another at a different time or place. Color variation in snail populations is maintained because in some habitats one color pattern is selected for because it is better camouflaged and in another habitat another pattern is selected for. In addition, color variants that are camouflaged in the green grass of spring are conspicuous in the dry grass of the fall.

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