[Leps-l] Monarch Armageddon revisited

[Foley, Patrick]

Directly addressing Paul's 3 points below (paraphrased to put them in scientifically interesting form):

1) Can a small number of transported Monarchs lead to Eastern Monarch Migration Collapse through parasite transport? The risk of parasite spillover from one Monarch population to another through human transport depends on unique characteristics of the two populations concerned. For the most part with Monarchs the danger seems small, but it is not zero. This follows from our general knowledge of parasite host race formation, from our experience with introductions of Bombus and from Sonia Altizer's actual data showing that different Monarch populations have different levels of parasitism. As we have discussed often in the past, there are many kinds of parasites from transposons to viruses to protozoa to mites to parasitoid insects. We do not know all the present Monarch parasites, and more will evolve or spillover to Monarchs in the future.

2)  Do lower corridor milkweed populations threaten EMMC? The eastern Monarch migration does not simply depend on the persistence of wintering habitat and milkweed-rich migratory corridors. It depends on the overall fitness conferred by a migratory strategy versus a nonmigratory strategy. If, as is true for many Monarchs and almost all other butterflies, the migratory corridors do not confer superior fitness, the Monarchs will evolve away from a long-distance strategy. We do not have, as far as I know, satisfactory information or models to know how close the threshold (long migrate vs short migrate strategy) we are. We do have evidence that the corridors and the winter sites have degraded as Monarch habitat.

3) Does climate change in Monarch winter sites threaten EMMC? I am not a climate scientist. The papers I have seen suggest more precipitation and more variability in wintering site climate. Either of these could discourage Monarch migration. Again, the issue is not whether Monarchs can survive, it is whether long distance migration confers higher fitness.

My overall guess is that climate change is likely to be the biggest factor in changing Monarch's migratory behavior. The parasite risk seems small at the moment, but we have seen epidemics destroy entire species and populations in the past (for example the American Chestnut, the inhabitants of Tierra del Fuego, some Bombus species), so it would be well to be cautious about claims of invulnerability. Migratory corridors are under substantial remodeling in the US, but hopefully, local and national efforts can help to correct that. We should be grateful to those who help.

I have appreciated the chance to discuss this interesting topic ( I do research on epidemiology, extinction and parasitism, though not on Monarchs), and, now that Paul has summed up his main points and I have also, I'm happy to leave further discussion to others.

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 11:45 AM
To: Leps List
Subject: Re: [Leps-l] [leps-talk] Monarch Armageddon

On Feb 20, 2013, at 11:19 AM, Foley, Patrick wrote:

> Paul, I was not trying to reply to you, point for point, I was
> making some general points that undermine the view
> that Monarch releases are totally safe.

Pat, we're getting way off track from the three monarch
migration extinction questions at hand:

1) Is there credible scientific basis underlying the beliefs of
Dr. Brower, Oberhauser and Taylor 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 field caught western
monarchs to the eastern USA?

2) Does professor Chip Taylor have a legitimate scientific
basis for telling the public and reporters that just because
there is less, but still alot, of milkweed growing on
midwestern farmland, the monarch migration could be
on the brink of collapse as he says or implies in these
videos?:

http://www.youtube.com/watch?v=qZXGRZMrsDU
http://www.features.ku.edu/monarchs/

3) Does any credible science exist to support the contention
that temperatures in the overwintering region of Mexico
could conceivably increase by a staggering and
unprecedented 3-4 degrees during the next 18 years
and (Chip Taylor's words} "eliminate most of the suitable
areas for overwintering because it would eliminate the
oyamel fir trees."?

So far, after several days of discussion, we see the answers
to all three questions are No.

So it appears it's time to end this discussion - although
bearing in mind that a new round of "monarch migration
could be threatened" type articles is very likely to appear
in the popular press within the next 1-3 weeks (i.e. articles
in the New York Times, Washington Post, Boston Globe,
Los Angeles Times, etc).

Paul Cherubini
El Dorado, Calif.
_______________________________________________
Leps-l mailing list
Leps-l at mailman.yale.edu
http://mailman.yale.edu/mailman/listinfo/leps-l