nonmelanistic

Nonmelanistic is an adjective used in biology to describe organisms that do not exhibit melanism—the accumulation of dark or black pigments that leads to a darker coloration. Nonmelanistic forms contrast with melanistic (black or dark) morphs and are often considered the standard or baseline phenotype within a species. The term is widely used in discussions of color variation, polymorphism, and mimicry in animals, though it may be applied to any pigment-related trait involving melanin.

Color polymorphism is common in various taxa, and many species have both melanistic and nonmelanistic individuals. A classic example is the peppered moth (Biston betularia), which shows light (nonmelanistic) and dark (melanistic) forms; in some environments, the nonmelanistic form is the ancestral state, while melanism arises via mutation and selection.

Genetically, melanism often results from mutations or regulatory changes that increase melanin production, whereas the nonmelanistic form reflects typical pigment expression. The inheritance pattern can be simple or complex, depending on the species and the specific genes involved.

Ecological and evolutionary significance varies by context. Melanism may provide advantages for camouflage, thermoregulation, or signaling in certain habitats, while nonmelanistic coloration may be favored in others. In general, nonmelanistic descriptions serve as a reference point for documenting pigment variation and for describing phenotypic diversity within populations.