Postindustrial Melanism in the Peppered Moth

Abstract

New data show the geographical pattern of frequency of the melanic morph carbonaria of the peppered moth, Biston betularia, in 1983-84. These frequencies are compared with data from 1952 to 1970. After 20 years of smoke control, the area of high melanic frequency has contracted to the northeast. The change indicates a disadvantage to carbonaria of about 12 percent compared with 20 years ago. Computer simulations, which do not include the assumption of heterozygote advantage, provide a good match to the surface for the period 1952 to 1970, and also the 1983-84 surface. Experiments on visual predation have been criticized as giving unrepresentative estimates of selection but they permit satisfactory simulations to be made.

Decline of melanism in two British moths: spatial, temporal and inter-specific variation

“…These possibilities were earlier discussed by Ford (1937Ford ( , 1953Ford ( , 1964 and by Kettlewell (1957Kettlewell ( , 1973) from a different perspective. More recently, it was noted that, as is apparent with the present estimates (Figure 3), the systematic pressure reducing melanic frequency appears more intense where the frequency was initially higher (Cook et al, 1986;Grant et al, 1998;Cook, 2003). A logical conclusion could be that selective predation itself declines as the environment becomes more rural, thus removing the need for additional counteracting selective forces.…”

Melanic morph frequency in the peppered moth in the Manchester area

“…A few years later, overall change in England and Wales was tracked by using values from a survey made in 19838 4 (Cook et al 1986). Individual samples were small, but they were widespread and allowed a morph frequency surface to be obtained by interpolation.…”

Melanism in Adalia ladybirds and declining air pollution in Birmingham

“…The decline in melanic A. bipunctata is associated with a similar selective disadvantage to that estimated at 12 per cent in B. betularia (Cook et a!., 1986), but the decrease in the carbonaria form of B. betularia is more closely correlated with sulphur dioxide pollution than smoke. Gaseous pollutants act, at least in part through effects on the recovery of epiphytic growtlI on the resting backgrounds of this cryptic moth (see e.g.…”

“…The substantial decline in melanic frequency in A. bipunctata began about 10 years earlier than that in a population of B. betularia at West Kirby near Liverpool (Clarke et a!., 1985) and more generally in this species in England and Wales (Lees, 1981;Cook et a!., 1986). The decline in melanic A. bipunctata is associated with a similar selective disadvantage to that estimated at 12 per cent in B. betularia (Cook et a!., 1986), but the decrease in the carbonaria form of B. betularia is more closely correlated with sulphur dioxide pollution than smoke.…”