butterfly-plant coevolution

John Grehan jrg13 at psu.edu
Wed Jan 9 21:05:03 EST 2002

Although I have not read the paper in question (but I will) and its been 
many years
since reading Ehirlich and Raven's piece I will make the mistake of jumping in
with a couple of off the cuff general comments (that I may regret). 
Apologies to
Valerie Passoa if they do not conform to her posting requirements.

>2) Janz and Nylin reconstruct the ancestral host plant as perhaps
>Fabaceae or at least a Rosid. (This point was made by Scott 1986 also).
>What about all those primitive Papilionids that eat primitive

Once I have a look at their paper I may be able to make a more informed
judgement, but in general terms I have noticed a penchant for regarding
the "ancestral host plant" relationship to be expressed as a specialist 
relationship which
then leads to others being considered "derived". The alternative 
possibility that
the ancestor was a generalist (i.e. the ancestor now represented as 
for example, may have feed on more than one plant group and these may have all
been "ancestral" to the current plant group) so all the current host
groups are in some way "derived".

Many years ago I wrote a critique of Ehirlich and Raven's paper. Of course 
it was rejected. It was perhaps rather naive in presentation but the basic 
points I still think are valid. The main question I think I posed was 
whether a congruent butterfly-host differentiation (e.g. congruent 
phylogenies), while perhaps evidence of a certain kind of 'coevolution' had 
necessarily anything to do with natural selection or supposed reciprocal 
sequence of host plant 'defense" and insect response (at least that's my 
memory of it).

>3) Why isn't there a Butterfly book like Mabberly's The Plant Book,
>listing Butterfly genera and their distribution world wide. Or some kind
>of world-wide catalog of species? Is someone working on this?

I seem to recall that there are some books out with this kind of 
information at least
for some butterfly groups, but I've not seen anything for all families and 
species in
one package. I agree it would be nice to see (if accurate).

John Grehan


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