rising@utzoo.uucp (Jim Rising) (02/11/88)
Apparently the first black specimen of a peppered moth was caught at
Manchester, England in 1848. Although there is only one generation
per year, by 1895 about 98% of the moths in the Manchester region
were black.
During the day, the moths rest against the sides of trees. The "typical"
moths are lichen-like in coloration, and cryptic against the trunks of
lichen-covered trees. The air pollution associated with industry of
Manchester and central UK killed off the lichens in heavily industrial
areas; as well, there was soot deposition on the tree trunks. Thus, in
those regions, the black moths are relatively cryptic. There is good
evidence that birds act as selecting agencies.
The change in 50 generation at Manchester could have been brought about
by a coefficient of selection against typical moths of .2.
There is also clinal variation in the frequency of the black moths, and
the black moths are still rare in rural, non-polluted areas. Also, as
a consequence of restrictive pollution laws, the lichens are returning
in the industrial areas, and--you guessed it--the typical moths are in-
creasing in those areas.
ALthough this is apparently an excellent example of natural selection, it
is not--as already noted--an example of speciation. The black morph
is apparently determined by a dominant allele at a single locus.
--Jim Rising
--
Name: Jim Rising
Mail: Dept. Zoology, Univ. Toronto
Toronto, Ontario, Canada M5S 1A1
UUCP: {allegra,ihnp4,linus,decvax}!utzoo!rising