Recent Boston Globe "monarchs are threatened" article

[Nick Grishin]

I do not understand, n

On Fri, 9 Jul 2004, Patrick Foley wrote:

> Paul,
> 
>     I claimed that the Eastern NA migration is more fragile than the 
> species' viability. You are arguing that it is not fragile at all. I 
> doubt that. If it were not fragile at all, why is it that so few 
> butterfly species show any similar migration?
>     You make an interesting point that migrations reappear in farflung 
> populations of the Monarch. That is well worth studying. Do you think it 
> is due to built-in genetically controlled tendencies? Do you think it is 
> a matter of immediate good decisionmaking by the butterflies? Is it a 
> vestige or an easily selectively reinforced set of traits? All good 
> questions. But if the eastern NA Monarchs do not achieve sufficient 
> Darwinian fitness by their migration, the migration will sputter out. As 
> it may have in untold other species. And it will sputter out either 
> because the wintering sites or the feeding sites become compromised.
> 
>     If the wintering site for the Eastern NA monarchs has no special 
> features, could you explain why the Monarchs don't overwinter in all the 
> closer (to the NA milkweeds) habitats on their routes? I gather that the 
> cool, but not frigid winter (similar to CA coast) helps to both lower 
> their metabolism, increasing their lifespans, and thaqt there are fewer 
> predators in these conditions. The fact that the eastern NA Monarchs 
> make such substantial migrations, despite their costs, suggests that the 
> payoff is pretty good, and that they cannot get it cheaper. In 
> California, such long migrations do not occur, probably because the 
> overwintering conditions are met along the coast.
> 
>     Paul, how are milkweed populations doing in the Midwestern US? You 
> are pretty sanguine concerning them? Does anyone have any data about them?
> 
> Patrick
> patfoley at csus.edu
> 
> Paul Cherubini wrote:
> 
> >Pat Foley wrote:
> >
> >  
> >
> >>But as we have cleared up several times on this list, the Monarch's
> >>Eastern NA migration behavior is a much more fragile thing. Why?
> >>1) This kind of migration is not common in butterflies. It
> >>apparently requires just the right conditions.
> >>    
> >>
> >
> >Fragile?  I'd say quite the opposite.  During the 19th century
> >monarchs were inadvertently introduced to several other temperate
> >latitude islands and continents around the world and
> >in each case seasonal migrations with overwintering clusters
> >developed that mirror those in North America.
> >Examples: southwestern Europe, Australia, New Zealand.
> >And within Australia itself, seasonal migrations with
> >overwintering clusters developed in three widely
> >geographically disjunct regions; Sydney, Adelaide and some
> >islands between Tasmania and Australia -- in just a matter of
> >decades.
> > 
> >  
> >
> >>2) These conditions include the availability of a wintering site with
> >>special features.
> >>    
> >>
> >
> >Special features?  I'd say quite the opposite.  In California and
> >around the world we have seen that practically any kind of
> >evergreen tree, either native or exotic, will provide adequate
> >overwintering cluster habitat.  And we have also seen monarchs
> >overwintering successfully in a rather wide range of climates.
> >Santa Barbara, California for example, has a considerably warmer,
> >less cloudy and less rainy fall / winter climate than the San
> >Francisco Bay Area yet monarchs overwinter by he tens of
> >thousands in both regions.  And we also see monarchs
> >overwintering successfully in highly developed and disturbed habitats
> >such as clumps of trees surrounded by residential subdivisions,
> >industrial buildings, factories, shopping centers and in cemeteries,
> >golf courses and city parks.
> >
> >  
> >
> >>3)  Chip Taylor is certainly correct that the elimination of
> >>the host plant will end the migration. Surely you are not
> >>arguing with that statement.
> >>Presumably you are claiming that milkweed populations will remain
> >>sufficient in the future even with increased intensity of "weed"
> >>control. How do you know this?
> >>    
> >>
> >
> >Well since 1996, the upper Midwest has been the region of the
> >USA with the most extensive plantings of herbicide resistant crops
> >and yet this also continues to be the same region with the most
> >intensive abundance of monarchs.  And last summer there was a
> >spectacular outbreak of Painted Ladies that occurred in Iowa and
> >surrounding States http://www.saber.net/~monarch/suv.jpg
> >In other words, a spectacular outbreak of Painted Ladies occurred
> >on the very same croplands where herbicide resistant crops are most
> >intensively grown.
> >
> >None of this surprises me because herbicide resistant crops provide
> >only an incremental improvement in weed control rather than a
> >revolutionary improvement.  Therefore I think monarchs scientists and
> >conservationists who tell newspaper reporters that herbicide resistant
> >crops could "threaten" or "could wipe out" milkweeds and could "threaten"
> >or "end the monarch migration" are being wildly unreasonable and dramatic.
> >Just like some of them were behaving 15 years ago:
> >http://www.saber.net/~monarch/extinction2.jpg
> >
> >Paul Cherubini
> >
> > 
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> >
> >  
> >
> 


 
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