Monarch extinction

[Paul Cherubini]

Ron Gatrelle wrote:

> If all the monarch overwintering sites in Mexico
> and Calif. were to be wiped out would D. plexippus become extinct? 

No. During the winter monarchs breed in Florida, the Bahamas,
West Indies, Gulf coast of the USA and Mexico, interior lowlands
of Mexico and in southern California, Baja California and southwestern
Arizona - quite a large area indeed!  In the 1960's, before the 
overwintering sites in Mexico had been discovered, Lincoln Brower 
believed monarchs from these winter breeding areas moved northward
in the spring and repopulated the northern latitude states - much as the
Queen butterfly is known to repopulate the central latitude states
in the spring.

After the Mexican overwintering sites were discovered, however,
Brower and others started promoting the idea that the entire monarch
migration phenomenon is a fragile thing totally dependent on 
successsful overwintering in Mexico. This is an exaggeration as
millions of monarchs would still be alive and breeding in the above 
named geographical areas during the winter if
someone nuked all the monarch overwintering sites in California and
Mexico. Also, monarch migratory populations have recovered
very rapidly - in a matter of 4-5 months - following rare events of 
catastrophic storm related mortality at the overwintering sites in both 
California and Mexico.

> Did the sedentary or migratory phase of monarch evolve first? 

The issue is not black and white because the continuously breeding
monarch populations in Florida, West Indies, Gulf Coast, etc, interbreed
with the migratory monarchs during the fall, winter and spring.
Even monarchs in Trinidad - which is way down near South America  -
are genetically indistinguishable from USA and Canada monarchs 
according to mitochrodrial DNA studies carried out by Andy Brower. 

Paul Cherubini

 
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