zagatti at versailles.inra.fr
Tue Sep 15 04:23:07 EDT 1998
Anne Kilmer wrote:
> Another factor that might be considered: jumping is sexy. When you
> consider natural selection, sometimes you fail to note that frivolous
> factor: attracting the other sex.
> This is not always frivolous, when one gets down to first causes. The
> alkaloids that tempt the female Monarch to yield, will protect the eggs
> from ants. She presumably does not know, so we cannot attribute purpose
> to her in this selection. Where we leave it, applying only logic, is
> that those who made this choice had grandchildren.
The theory of sexual selection was considered by Darwin himself
as a part of natural selection theory. In fact, the evolution of
male seducing characters is always balanced by their value in
terms of predation avoidance, food access and so on.
A classical example is given by the antlers of the giant deer
Megaceros, which became extinct when its antlers did not fit
anymore with a new environment. I guess
this example is historically wrong, but it gives a good
illustration of the phenomenon.
Good entomological examples are given by the androconia of
male lepidoptera. When a species has developed huge, conspicuous
androconia, this is frequently associated with sequestration of
toxic substances and their accumulation in the androconia.
Thus these androconia share a seducing, intraspecific function,
and a defensive, interspecific function. This culminates in the
very toxic arctiids Creatonotos, with androconia (coremata)
five times longer than moth body when fully extended.
This the case in danaids too. Have a look at the page I'm
preparing for the monarch:
several bibliographic reviews are given on the page
(the butterfly pages are not on line yet, some data are still missing).
All the best,
INRA Unite de Phytopharmacie et Mediateurs Chimiques
78026 Versailles Cedex
Tel: (33) 1 30 83 31 18
e-mail zagatti at versailles.inra.fr
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