Peppered Moths - round 2 (part 2 of 2)

Donald Frack (dcfrack@sowest.net)
Mon, 5 Apr 1999 20:55:00 -0700

Peppered Moths - round 2 (part 2 of 2)

Below is a reply to me from Michael Majerus regarding a copy of Jonathan
Wells response to the documents I posted 3/30/1999.

Majerus quotes himself in full to contradict Wells on the first point.
Wells changed "**précised** pepper moth story" to "**basic** pepper moth
story" (Majerus does not point this word change out explicitly, which is why
I mention it here). Précis (accent over e) means "a concise summary of a
book, article or document; an abstract." Majerus makes clear that he means
the general textbook stories leave out details, and that this is a matter of
limited space. His Conclusion to the chapter begins with: "The case of the
peppered moth is undoubtedly more complex and fascinating than most biology
textbooks have space to relate." This distinction is why he chose the word
carefully that Wells changed. I'm not sure everyone is familiar with the
term Majerus used.

Creationists in the group will obviously put their own spin on Majerus's use
of "fake" discussing photos.

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***** from Michael Majerus

Dear Donald, Just a quick note to say that the response you received is
fairly typical of what happens when people who have no knowledge or
experience of an organism or group of organisms, think that they 'know'
what is going on. As usual, the response is subjective and ill-informed.
I usually find that answering people who put their trust in subjective
argument is unrewarding, but as you at least seem to want a balanced and
objective appraisal of this case, I think that one or two errors in the
response should be corrected.

Taking Wells' points in turn.

Preamble about my book and quotes from it: Dr Wells wrote:

"Majerus's book includes a chapter entitled "The peppered moth story
dissected." Surprisingly, on the first page (117) of that chapter appear
both of the following statements:

"...the basic peppered moth story is wrong, inaccurate, or incomplete, with
respect to most of the story's component parts."

and

"...in my view....differential bird predation...in habitats affected by
industrial pollution to different degrees, is the primary influence on the
evolution of melanism in the peppered moth.""

It is worth showing the way in which Dr Wells tries to distort what is said
by someone else in good faith, by giving the whole of the sentence from
which the first quote was culled, and the ensuing sentence....
"The findings of these scientists show that the precised description of the
peppered moth story is wrong, inaccurate, or incomplete, with respect to
most of the story's component parts. When details of the genetics,
behaviour, and ecology of this moth are taken into account, the resulting
story is one of greater complexity, and in many ways greater interest, than
the simple story that is usually related.

In other words, it is the text book precised account of the peppered moth
story that I critise, not the scientific accounts published in peer
reviewed scientific journals. Dr Wells as a scientist should understand
the difference between the two, and should not attempt to take quotations
out of context for his own ends. That is a policy followed by the worst
aspects of the gutter press.

1) The frequency of the melanic form of the peppered moth did not decline in
the 1950s: The decline began about a decade later. This would be predicted
by the selective predation/crypsis hypothesis, but not by the direct effects
of mutagenic pollutants hypothesis.

2) The mark release and recapture experiments were completely independent
of the predation experiments on tree trunks. This critically undermine's
Dr Wells' rationale. Moths were released at dawn (before sunrise) and
allowed to take up natural resting sites. Recaptures were by mercury
vapour and pheromone traps. The reciprocal nature of the proportions of
the forms that were recaptured in the polluted and unpolluted woods give,
to my mind, the strongest evidence we have that there is differential
selective elimination of the two forms in the different environments.

3) This depends upon who you read. Although Grant and Clarke argue that
lichen growth has not increased since the clean air acts, others (see for
example Cook et al, 1990, Melanic moths and changes in epiphytic vegetation
in north-west England and north Wales, Biol. J. Linn. Soc., 39, 343-354)
show that the lichen flora has increased subsequent to antipollution
legislation, and their has been a corresponding increase in the pale form
of the peppered moth.

4) This is just wrong. Dr Wells' who gives the impression in his response
that he has read my book, obviously has not. If he had, he would have seen
that in Tables 6.1 and 6.2 I myself have recorded 168 peppered moths on
tree trunks or at trunk/branch joins. If Dr Wells' wishes his views to be
taken seriously, he should ensure that his research is thorough.

The following paragraph is full of subjective innuendo: e.g. "apparently
disorientated" moths, "Surprised birds". Again there are errors as well.
Kettlewell did know that peppered moths did not most usually rest on tree
trunks (see Majerus 1998 page 123 for quotation and reference).

Evidence of selective predation in the peppered moth is not lacking. It is
just not provided in the quick text book descriptions of the peppered moth.
How can it be. I have read some 500 papers on melanism in the
Lepidoptera. In total, these papers probably amount to about 8000 pages,
ad the story is condensed into a few paragraphs in most textbooks for
schools. Even in my own book, I could only give a review of the case
covering about 60 pages including illustrations.

The older hypothesis that melanism was induced by pollutants was
discredited because eslop Hassison's experiments lacked appropriate
controls, and his results could not be replicated, despite several
attempts. Furthermore, the levels of mutagenesis that he recorded are
several times higher than those produced by doses of radiation that induce
complete sterility in fruit flies (see E.B. Ford (1964) Ecological Genetics
for full critical review).

Finally, I agree with Dr Wells that photographs of two peppered moths
staged on backgrounds for effect should say they have been done purely for
illustrative purposes. I have many times, in undergraduate lectures,
pointed out that photographs of the type that appear in so many text books
are faked. However, I would point out that none of the photographs of
live peppered moths taken by myself, which appear in the book were staged.
All show peppered moths where they were found in the wild.

End-note: It is difficult to have an informed discussion of a complicated
ecological system with those who have little or no experience of the
system. My advice to anyone who wishes to obtain a fully objective view of
this case is to a) read the primary papers that I based my review upon, and
any other relevant papers, and b) gain some experience of this moth and its
habits in the wild. Of all the people I know, including both amateur and
professional entomologists who have experience of this moth, I know of none
who doubts that differential bird predation is of primary importance in the
spread and decline of melanism in the peppered moth.

I hope that this is some use to you, Donald, and that it encourages more
people to look at the case of the peppered moth with an open mind. If it
can help interest a few more people in moths and butterflies, that is all
to the good.

Best wishes, and Happy Easter.

Mike Majerus