Presented by Samantha Sharp

The Story

Industrial melanism

Peppered moth – Biston betularia (“typical”) and carbonaria (“melanic”)

Pollution, camouflage and bird predation

In the Beginning

J.W. Tutt, 1896Observations on camouflage

Proposed selective predation hypothesis

Bernard Kettlewell, 1950sCatch-and-release experiments

Variables:• moths’ “conspicuousness” to humans

• birds’ behavior in eating moths

• how many moths retrieved at the end

Criticisms of Kettlewell

Experimental flawsMoths released during day

Unnatural resting place

High moth density

Fraud? – HooperPressure from mentor Ford

Need to “prove” Darwinism

Defense of Kettlewell

Kettlewell was good for his day – Shapiro

Attack on Wells – Coyne and Grant

Not all about lichens – Grant

The Problems

Occurrence of melanic forms increased in areas where pollution didn’t

Are these areas prevalent or not?

Typical forms returned before lichens did

Incomplete disappearance of typicals

The Experiments

Harrison – induced melanism in adults

Contrast/conflict hypothesis

Selective predation

Alternative Explanations

Differential predation with gene flow

Natural selection with unknown cause – Grant

Induced trait, neutral, negative or adaptive change – Sargent, Miller & Lambert

Melanics have higher viability, stopped by visual predation – Ford

Overreaction?

Grant – people often discard rather than change

Wells – don’t teach melanism

If this is wrong, what else? (Hooper)

My Analysis

Evolution? Yes. Natural selection? Yes.Harrison’s induced changes?Speed of changes – Grant vs. Sargent, Miller & Lambert

Flaws? Yes. Fraud? No.

Similar to global warming controversyConflicting analysesOverreaction of opponents

In the End…“We still have work to do. We do not all agree about the relative roles of contributing factors, such as the flow of genes between moth populations in different regions, the importance of lichens on trees, where on trees moths might hide from predators, how important is differential predation, and so on. As in any branch of science, participants endlessly debate interpretations. Such wrangling is the norm, and it stimulates additional research. That is how we make progress.” - B. Grant

SourcesCoyne, J. A. 2001. Creationism by stealth. Nature. 410: 745-746.

Grant, B. 2000. Charges of fraud misleading. The Pratt Tribune. December 13 (Online Archives).

Grant, B. S. 1999. Fine tuning the peppered moth paradigm. Evolution. 53: 980-984.

Grant, B. S. 2002. Sour grapes of wrath. Science. 297: 940-941.

Harrison, J.W.H., and Garrett, F.C. (1926). The Induction of Melanism in the Lepidoptera and Its Subsequent Inheritance. Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character, 99(696), 241-263. From JSTOR website http://www.jstor.org/stable/81092

Hooper, J. 2002. Of Moths and Men: Intrigue, Tragedy and the Peppered Moth. Fourth Estate. New York.

Sargent, T. D., Miller, C. D. and D. M. Lambert. 1998. The 'classical' explanation of industrial melanism. Assessing the evidence. Evol. Biol. 30: 299-322.

Shapiro, A. M.. 2002. Paint it black. Evolution. 56: 1885-1886.

Wells, J. 1999. Second thoughts about peppered moths. The Scientist. 13.

Wells, J. 2003. Second thoughts about peppered moths. Origins website http://www.origins.org/articles/wells_pepmoth.html