competition for food, literature question

[Cris Guppy & Aud Fischer]

The only two examples I can think of are:
(1) pest outbreaks that completely defoliate the foodplants (forest tent
caterpillars, gypsy moth);
(2) Pierids that feed on Cruciferae (wild mustards), such as those showing
the "red egg syndrome" of Shapiro. In California females avoid laying eggs
on plants that already have red eggs (Pierid eggs over 24 hours old) on
them. Larger larvae cannabilize smaller larvae, which MAY in turn be the
result of competition for food (wild mustard plants are frequently too small
for a single larva to mature on, much less many larvae). Alternatively the
larger larvae may just grow better with a good protein meal.

In general though there seems to be very little competition for food, at
least in temperate areas. Larvae are spread too thin. The avoidance of
plants with red eggs on them does not appear to be the case for the same
species of Pierids in British Columbia as were studied in California.


I am not aware of any documented examples of population size being limited
by food supply. However my general impression is that for an area of equal
size, on average areas with more foodplants have more adult butterflies.
This may not be the result of competition for food however.

-----Original Message-----
From: Kondla, Norbert FOR:EX <Norbert.Kondla at gems3.gov.bc.ca>
To: 'lepsl' <leps-l at lists.yale.edu>
Date: May 10, 2000 4:21 PM
Subject: competition for food, literature question


>I recently read a stated concern about butterfly species x competing with
>another species for food supply.  I am a little sceptical about this view.
>Even when dealing with populations of one butterfly species, I do not
recall
>running across any empirical data to suggest that food supply is any kind
of
>real limiting factor in butterfly abundance (of course in mathematical
>models anything can be turned into a limiting factor).  Have I missed some
>key literature ? Anyone out there that can share some references with data
>to show population limitation due to food supply (amount). Conceptually I
>could see such a thing in the case of a butterfly population that is
>dependent on one endangered host plant but darned if I can think of a
>documented example.  Thanks in advance for sharing your knowledge.
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Norbert Kondla  P.Biol., RPBio.
>Forest Ecosystem Specialist, Ministry of Environment
>845 Columbia Avenue, Castlegar, British Columbia V1N 1H3
>Phone 250-365-8610
>Mailto:Norbert.Kondla at gems3.gov.bc.ca
>http://www.env.gov.bc.ca
>
>