Peppered moth genetics
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The peppered moth has both melanic and non-melanic forms. This has importance to the case study of evolution mentioned below. A particular morph can be indicated in a standard way by following the species name in the form "f. morph".
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Morphs
NB: It is a common mistake to confuse the name of the morph with that of the species or subspecies, hence mistakes such as "Biston carbonaria" and "Biston betularia carbonaria". This might lead to confusion that there has been demonstrable speciation in the case study mentioned below. This is not the case; individuals of each morph can breed with individuals of all other morphs, and hence there is only one species.
In Europe, there are three morphs:
- f. typica; the typical white morph (also known as f. betularia)
- f. carbonaria the melanic black morph, (also previously known as f. doubledayaria)
- f. medionigra, an intermediate semi-melanic morph.
In North America, the typical white morph is also known as f. typica; the melanic black morph is f. swettaria.
In Japan, no melanic morphs have been recorded; they are all f. typica.
Europe
Breeding experiments have shown that in Biston betularia betularia, the allele for melanism producing f. carbonaria is controlled by a single locus. The melanic allele is dominant to the non-melanic allele. This situation is however, somewhat complicated by the presence of three other alleles that produce indistinguishable morphs of f. medionigra. These are of intermediate dominance, but this is not complete (Majerus, 1998).
In Biston betularia cognataria, the melanic allele (producing f. swettaria) is similarly dominant to the non-melanic allele. There are also some intermediate morphs.
America
Biochemistry
Unfortunately, the molecular genetics and biochemistry of melanism in this species are at present unknown. True (2003) reviews this and suggests work based on candidate genes from other insects such as the fruit fly, Drosophila melanogaster. For example, Nachmann et al did a similar thing with whatsits.