Government views Monarch Butterfly Releases as a threat toWesternMilkweeds

John Grehan jrg13 at
Thu Dec 13 07:46:49 EST 2001

At 09:44 PM 12/12/01 -0700, you wrote:
>Paul Cherubini wrote:
> >
> >                                                          Dr. Vane-Wright
> > attributes this rapid spread across the Pacfic and Atlantic
> > in the mid-1800's to hitch-hiking on the new fast moving steam
> > powered ships that replaced the old slow wind powered ships.
>I have not read Vane-Wright's abstract and so I do not know if this was
>his opinion, or hard scientific data.  If it borders on an educated
>supposition or guess, than you are on weak grounds to use this to then
> > So yes I agree there are sometimes unimagined consequences of
> > human activity on butterfly abundance and distribution - including
> > consistently positive outcomes for weedy species such as the Monarch.

My recollection is that Vane-Wright's was not based on 'hard data' but that 
does not seem to disqualify Paul's inference. The Monarch may have flown 
across the Pacific without hitching rides on boats, but its establishment 
in places like New Zealand was apparently not possible without human 
introduction of milkweeds (unless there was some obscure locally endemic 
alternative). So this particular correlation seems to be one of cause and 

The ecological concept of a "weedy species" is context related so it is a 
relative rather than definitive. Whether it may be applied to the Monarch I 
would not be in a position to judge, but the fact that it feeds on milkweed 
that thrives in disturbed conditions does not necessarily mean that the 
term is applicable to the Monarch since it is not that "weedy" in its 
host-plant options (i.e. with animals "weedy" species often have broad or 
generalized feeding options). However as I do not specialize in ecology I 
would not be surprised to find this characterization questioned.

John Grehan


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