industrial melanism


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industrial melanism

a phenomenon found in several groups, notably moths, in which a heavily pigmented variant (a MORPH) becomes the most frequent type in an area with heavy, man-made atmospheric pollution. Melanism is an excellent example of MICROEVOLUTION, in that rapid evolutionary change has been brought about by strong forces of natural selection acting in favour of a dominant allele for melanism. The agents of selection against moths (such as the peppered moth Biston betularia) are birds, which predate more heavily those types resting against a colour-contrasting background: poorly pigmented forms resting on sooty tree trunks, for example. The proportion of melanics to nonmelanics in an area is correlated with the level of pollution, although neither type appears to be completely absent in any environment, creating a GENETIC POLYMORPHISM. See also KETTLEWELL.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
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These butterflies are influenced by natural selection to choose an appropriate subtract to land on, and if their ability to select it is shown to be deliberate, then new valuable evidence may be available to support the concept of industrial melanism. Hamadryas feronia farinulenta (Fruhstorfer 1916) is a good example of a butterfly that is known to be selective with respect to its perching site (Young 1974, Jenkins 1983, Monge-Najera et al.
Majerus asserted that we must dismiss industrial melanism in Biston Betularia (peppered moths) as an exemplar of natural selection but that the basic tenets of ecological genetics and evolution forwarded by Kettlewell and ford still stood firm.
Well-known examples include industrial melanism in moths (Kettlewell 1973); cryptic adaptations among many Sargasso Sea animals (various authors); small tubular bodies bearing adhesive glands among many phyla of interstitial organisms (Swedmark 1964); smooth-edged leaves of tropical trees (various authors); streamlined, flippered shapes among sympatric aquatic fish, birds, and mammals (Romer 1966); large size and short extremities in Arctic mammals and birds (Bergmann 1847); and thick shells bearing varices and nodules (protection against crab predators) among various families of tropical marine snails (Vermeij 1978).
Spatial distribution and sound production in five species of cryptic tropical butterflies (Hamadryas, Lepidoptera: Nymphalidae): Implication for the industrial melanism debate.

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