The introduction of the Clean Air Acts (1950s) provided further support 9, whereby pollution declined, lichen populations recovered, and there has since been a rise in the frequency of typica and a decline in carbonaria 10. Further work around this time 7, 8 supported Kettlewell and found that, despite persisting at frequencies as high as 80%, carbonaria still incurred a selective disadvantage in unpolluted areas. This was supported by the classic work of Kettlewell 5, 6, who demonstrated strong selection against typica in polluted woodland and against carbonaria in unpolluted woodland where lichen persisted. The former is widely thought to have been well camouflaged against birds on trees where atmospheric pollution had killed off the lichen and soot particulates coated the bark, with typica effectively hidden on lichen-covered trunks and branches in unpolluted woodland. 1760–1840), there was a rise of a new dark melanic ( carbonaria) form in conjunction with a corresponding decline of the pale ( typica) morph 4. Arguably, the most important example of evolution in action is that of industrial melanism and the peppered moth ( Biston betularia). Animal defensive coloration has long provided flagship examples to illustrate and defend evolution and adaptation, including early work by Bates and Wallace on mimicry and camouflage 2, 3. Across nature, many taxa have evolved camouflage to avoid detection or recognition 1.
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