industrial melanism The development of melanic forms of organisms in response to soot and sulphur dioxide pollution. Industrial melanism is especially associated with various moth species and was first noted early in the 19th century. In the 1950s, studies by H. B. D. Kettlewell on the moth Biston betularia showed that melanism is a simple inherited trait favoured by natural selection in soot-polluted environments, where dark colouring gives better camouflage and so better protection from predators. In time the proportion of melamc forms increases in such polluted environments. The reverse process–selection in favour of pale forms–occurs in pollution-free environments where the paler, speckled form is better concealed on the tree lichens on which it settles. With appropriate calibration, the extent of melanism in a population may thus be used as an indicator of industrial pollution. See also INDICATOR SPECIES.

industrial melanism The development of melanic forms of organisms in response to soot and sulphur dioxide pollution. Industrial melanism is especially associated with various moth species and was first noted early in the nineteenth century. In the 1950s, studies by H. B. D. Kettlewell on the moth Biston betularia showed that melanism is a simple inherited trait favoured by natural selection in soot-polluted environments, where dark colouring gives better camouflage and so better protection from predators. In time the proportion of melanic forms increases in such polluted environments. The reverse process (i.e. selection in favour of pale forms) occurs in pollution-free environments where the paler, speckled form is better concealed on the tree lichens on which it settles. With appropriate calibration, the extent of melanism in a population may thus be used as an indicator of industrial pollution.

industrial melanism The increase of melanic (dark) forms of an animal in areas darkened by industrial pollution. The example most often quoted is that of the peppered moth (Biston betularia), melanic forms of which markedly increased in the industrial north of England during the 19th century. Experiments have shown that the dark forms increase in polluted regions because they are less easily seen by birds against a dark background; conversely the paler forms survive better in unpolluted areas. See also directional selection.