Biston betularia (peppered moth)

Decline of the melanic phenotype from 1959 to 2003

Use the slider to set the selection coefficient s in the model, which assumes that the melanic form is selected against with selection coefficient s.

Can you find a single value of s that matches the points, which measure the frequency of the melanic form each year in a single place (West Kirby, near Liverpool, England). You may find that allowing the selection coefficient to change in 1976 helps in fitting the model to the empirical measurements.

Does the best fitting model assume a


The data for the points are from Clarke, Cyril A., Bruce Grant, Frieda M. M. Clarke, and Takahiro Asami. 1994. A long term assessment of Biston betularia (L.) in one UK locality (Caldy Common near West Kirby, Wirral), 1959-1993, and glimpses elsewhere. The Linnean 10(2):18-26. Only data from mercury vapor lights was used from Appendix I. Values after 1993 were obtained by eye-balling Figure 2 in Cook, Laurence M. 2003. The rise and fall of the carbonaria form of the peppered moth. Quarterly Review of Biology 78(4):399-417.


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