Alternative explanations Industrial melanism

immunity

industrial melanism has been reported in black arches moth, lymantria monacha. in 1921, richard goldschmidt argued observed increase in melanic form not have been caused mutation pressure alone, required selective advantage unknown cause: did not consider camouflage explanation.

a century later, suggested moth s industrial melanism might, in addition (pleiotropy) providing camouflage well-known protective dark coloration , confer better immunity toxic chemicals industrial pollution. darker forms have stronger immune response foreign objects, melanic pigment involved in encapsulation of foreign bodies.

thermal advantage

melanic forms of two-spot ladybird adalia bipunctata frequent in , near cities, , rare in unpolluted countryside, appear industrial. ladybirds aposematic (with conspicuous warning coloration), camouflage cannot explain distribution. proposed explanation melanic forms have thermal advantage. argued directly linked pollution aspect of industrialization, since smoke , particulates in air reduce amount of sunlight reaches habitats of these species. melanic phenotypes should favoured natural selection, dark coloration absorbs limited sunlight better. in colder environments, thermal advantages of industrial melanism might increase activity , likelihood mate. in netherlands, melanic a. bipunctata had distinct mating advantage on non-melanic form. however, thermal melanism fails explain distribution of species near helsinki city forms relatively warm heat island , while near finnish coast there more sunlight more melanism, selective pressure driving melanism requires different explanation, @ least in region.