[Leps-l] [leps-talk] Monarch Armageddon

[Foley, Patrick]

I enjoy your rhetorical device "the opposite is true", but it does not hold up well.

Monarchs are unlikely to pay attention to latitude lines. You probably recognize that the future climate zones will not be the same as they are today. That is one reason for the uncertainty I refer to. US Development and Mexican land use change also create uncertainty.

The migratory distances of Monarchs in California are very different than those in Eastern North America. If people are worried about the collapse of the Eastern migration down to a diversity of short migrations, why wouldn't the western migrations support that worry? Admittedly the California coast is cold compared to the Eastern seaboard, but there are plenty of dark hollows in the Appalachians that could conceivably offer overwintering sites.

Your claims about the Mexican overwintering sites go against published literature. Could you provide some published scientific literature to support your claim?

Again, no one I know is worried about the Monarch's persistence. Some people very reasonably worry that the great long-distance Eastern migration might dwindle away if, as you recognize happens elsewhere, the Monarchs find some shorter migration gives them higher fitness. Why is this point so hard for you to grasp?

Patrick

Patrick Foley
bees, fleas, flowers, disease
patfoley at csus.edu
________________________________________
From: leps-l-bounces at mailman.yale.edu [leps-l-bounces at mailman.yale.edu] on behalf of Paul Cherubini [monarch at saber.net]
Sent: Friday, February 15, 2013 2:12 AM
To: Leps List
Subject: Re: [Leps-l] [leps-talk] Monarch Armageddon

On Feb 14, 2013, at 11:43 PM, Foley, Patrick wrote:

> Every entomologist knows they are not endangered.
> What is poorly known is why _some_ Monarchs regularly
> migrate, and whether natural selection in the future
> will continue to encourage this migratory behavior.

Pat,  the opposite is true; it's been known
for years that all monarchs worldwide at temperate
zone latitudes (higher than approximately
28-29 degrees N or S latitude) are migratory; i.e. that
nearly all of them reliably enter and stay in reproductive
diapause in the late summer or early fall and seek
out diapause sites (places with a refrigerator like late
fall and winter climate). There is a small percentage of fall
butterflies that breaks diapause and lay eggs, but
those butterflies are migrants too that
exploit the small amount of milkweed that exists
en route to and near the overwintering sites.
Their offspring are migratory.

> Many Monarch populations do not migrate readily.

See above; i.e. no monarch populations anywhere in the
world situated higher than approximately 28-29 degrees
N or S latitude fail to enter reproductive diapause and
migrate to diapause sites in the late summer or early
fall (date of onset of diapause varies with latitude).

> Why is it so obvious that the appropriate natural
> selection conditions will continue to apply, when
> this migratory strategy is rare and not fully understood?

The opposite is true; i.e. worldwide at temperate zone
latitudes monarchs are seasonally diapausal and
migratory.

> There certainly has been serious loss of Mexican
> overwintering habitat.

The opposite is true and that's the reason why
no photographs exist substantiating this alledged
"serious loss of Mexican overwintering habitat."

> The issue is whether a Monarchs overall fitness
> is best served by migrating to an uncertain winter
> site through a patchy and uncertain milkweed
> landscape.

Monarchs don't migrate to "uncertain winter sites"
to begin with.  They migrate to broad geographical
expanses of land where the macroclimatic conditions
are similar to those of a refrigerator.  Then upon arriving
in those regions they opportunistically seek out and
cluster in most any clump of trees or tall bushes available
like golf course trees in Los Angeles or San
Francisco or a city park or cemetery in Christchurch,
New Zealand
http://i85.photobucket.com/albums/k75/4af/ccstj.jpg
http://i85.photobucket.com/albums/k75/4af/ccruru.jpg
or a vast forest covered mountains in Mexico:
http://i85.photobucket.com/albums/k75/4af/hera.jpg
http://i85.photobucket.com/albums/k75/4af/157Xe.jpg

There are actually so many eucalyptus/pine/cypress
groves that could serve at winter sites in the two most
heavily urbanized areas of California (San Francisco Bay
Area and Los Angeles) that no one has had the time
and stamina to check them all for monarchs. So there
no shortage of usuable winter cluster groves. Indeed,
as Fred Heath pointed out earlier today, the monarchs
hardly use the native coastal trees like the sycamore
groves that are still available because they find
the non-native Australian eucalyptus better suited to
their needs. Here is a video of a sycamore winter site
that the monarchs hardly use because so much
eucalyptus is available in the same coastal region:
http://www.youtube.com/watch?v=JUJPHHhZVrY

Monarchs even overwinter in low desert areas
like the Saline Valley near Death Valley
Ground view:
http://i636.photobucket.com/albums/uu87/4ALC/salinea_zpsa3f7820a.jpg
Aerial view: http://imageshack.us/a/img580/3376/salinec.jpg

With regard to finding "patchy" milkweed, monarchs routinely
find patches at locations that are remote and where it
is otherwise uncommon.  Like near the 9,000 foot summits
of the Trinity Alps of northwestern California (Art
Shapiro, pers. comm) the shoreline areas of Mono Lake in
the eastern Sierra Nevada mountains
http://i85.photobucket.com/albums/k75/4af/monob.jpg
Portland, Oregon railroad tracks:
http://i636.photobucket.com/albums/uu87/4ALC/pyleg.jpg
Seattle, Washington railroad tracks:
http://i636.photobucket.com/albums/uu87/4ALC/pylec.jpg
Roadsides high in the Colorado Rockies:
http://i85.photobucket.com/albums/k75/4af/coloi.jpg

> For some Monarchs it makes sense to stay in one
> predictable habitat. This already happens in warm
> areas such as Australia, the Caribbean etc.

Non-migratory monarchs exist only at latitudes
lower than about 27 degrees North and even some
of those monarchs migrate altitudinally (e.g Costa Rica).

> With a little global warming and a lot of habitat
> destruction, the Monarch migratory strategy may
> be the wrong one. This is the issue, not whether
> somebody was once wrong on the internet.

Not a reasonable scenario given the facts above
about monarch reproductive physiology at temperate
zone latitudes.

> Doesn't it bother you a little that we do not yet
> understand why so few butterflies migrate regularly?

Worldwide, Danaid butterflies commonly migrate
seasonally either latitudinally or altitudinally
(or both).

Paul Cherubini
El Dorado, Calif.
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