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

[Foley, Patrick]

Pyle et al. (2010, Xerces Society) estimate commercial Monarch release at about 11 million butterflies/year.

Pathogen and parasite spillover is now well documented from commercial to wild bumblebees (see reviews by Altizer 2012 in the book New Directions in Conservation Medicine and elsewhere). The effect on several North American Bombus species has been enormous  (Robin Thorp).

Sonia Altizer et al.  (2000 in ecological Entomology) have shown that nonmigratory South Florida Monarchs show higher protozoan parasite levels than the Western short-distance migrants, and these show higher parasite loads than the long-distance Eastern Monarch migrants. This data can be interpreted several ways: 1) long distance migrants are doing great!, 2) different Monarch populations have different parasite loads, so mixing them might not be wise, 3) parasite load is low for long distance migrants, because their physiological demands cause additional natural selection, culling out the highly stressed. Explanations 2 and 3 give pause to the notion that Monarchs are panmictic, no-worries fellow travelers. Explanation 3) suggests that parasite load works to select against migration.

Even given this information, it is not at all certain that the Eastern Monarch migration will be affected by commercial parasite spillover. But is far from impossible. Long-distance migration in butterflies is a rare, dangerous strategy that depends on natural conditions which we do not entirely understand. Those conditions are changing for Monarchs, and I do not see why we should be so certain that Monarchs will defy the natural selective pressures that discourage  other butterflies.

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: Wednesday, February 20, 2013 8:52 AM
To: Leps List
Subject: Re: [Leps-l] [leps-talk] Monarch Armageddon

On Feb 20, 2013, at 7:40 AM, Foley, Patrick wrote:

> New pathogens and parasites arise in populations by
> mutation or host switching. Their transmission to other
> populations sometimes has disproportionate effects.
> This is clear for many species including B. occidentalis,
> even highly mobile ones such as our own. Monarchs
> are not fully panmictic, even in temperate areas,
> despite lots of natural mixing.

Pat, over five monarch genetics studies (including this
2012 study*) have failed to find genetic differences
between eastern and western monarchs.   But even if
it was true that eastern and western monarchs are not
fully panmictic you, Brower, Oberhauser and Taylor have
not explained how it could be biologically possible for a
few citizen scientists  like myself to inadvertently cause
the collapse of the whole eastern migration-overwintering
phenomenon via shipping a few thousand western
monarchs to the eastern USA.

The bumblebee, Bombus occidentalis, did not suffer
a population decline here in the USA because humans
transported a native western USA bumblebee disease or
parasite to the eastern USA or vice versa.  So the Bombus
situation cannot be legitimately compared to the human
assisted west to east monarch transfer issue.

Thus we continue to see there is no credible scientific basis
underlying the beliefs of Brower, Oberhauser and Taylor
that a few that a few citizen scientists like myself could
inadvertently cause the collapse of the whole eastern
monarch migration-overwintering phenomenon via shipping
a few thousand wild caught western monarchs to the
eastern USA.

Paul Cherubini
El Dorado, Calif.

*Lack of genetic differentiation between monarch
butterflies with divergent migration destinations
Molecular Ecology 21, 3433-3444 (2012)
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