Government views Monarch Butterfly Releases as a threat to Western Milkweeds
patfoley at csus.edu
Sat Dec 8 22:00:05 EST 2001
Paul and other friends of Monarch numbers,
The contribution of this year's releases to the target gene pool will presumably
continue to influence next year's population. And so on. If the location-unique
alleles are presently selectively neutral (this is not to say neutral forever),
they will on average then build up in the target population to the point where they
would be noticeable. In fact until the source and target populations are
homogeneous (for _neutral_ alleles only!). The cumulative homogenizing effects of
even a small amount of migration on otherwise separated populations is astonishing.
Some models require only one migrant per generation to bring about long-term
homogeneity (Crow and Kimura 1970, p 269, Maruyama 1977 ch 11).
I want to emphasize that I am presently only arguing that releases hurt science.
The more important problem is the risk to populations of disease, transposons,
runaway sexual selection, lack of isolation for speciation and effects which we
have not yet thought of.
As often happens in environmentalist-development debates, one side is not worried
about cumulative impacts, because the immediate effects seem so small. Lomborg, in
his recent book the Skeptical Environmentalist, argues that an extinction rate of
0.7% per 50 years is manageable and hardly worthy of hysteria. To me, this
extinction rate will lead to 13% of the species on earth going extinct over the
next 1000 years. (exp(-0.007*20 half-centuries)= 0.87). If this doesn't trouble
you, consider the results of another 6000 years of human history. You should only
worry about the environment if you are rooting, as I am, for human civilization to
last ... or at least start.
patfoley at csus.edu
Paul Cherubini wrote:
> Dr. Pat Foley http://www.csus.edu/indiv/f/foleyp/index.html wrote:
> > Clearly Bruce and Paul want to have it both ways: 1) Our techniques
> > are so bad that we won't even sample the release effects and 2) The
> > old flawed techniques are giving way to new and improved techniques.
> Pat, Dr. Bruce Walsh http://nitro.biosci.arizona.edu/ wrote:
> > unless the released material makes up a significant fraction of the local
> > breeding population (at least over 1 percent and likely over 5 percent),
> > it is unlikely to be obtained in a random population sample.
> So how about if we try and model the probability of sampling a released
> monarch? Since Dr, Karen Oberhauser studies monarchs in Minneapolis,
> Minnesota, let look at that area.
> The greater Minneapolis-St. Paul metropolitan area measures 25 x 25
> miles = 625 square miles. Roughly 700,000 people live in this area.
> The local monarch breeding population in this area of 625 square miles
> in late summer contains roughly.62,500 monarchs (i.e. there are about
> 5,000,000 monarchs in the lower two thirds of Minnesota in late
> summer = an area of 50,000 square miles =100 monarchs per square mile)
> Approximately 200,000 monarch butterflies are shipped interstate to all
> parts of the USA each year by butterfly breeders. Since the USA population
> is 270,000,000, and the Minneapolis area population is 700,000, roughly
> 518 monarchs out of those 200,000 get shipped to Minneapolis each year.
> These 518 are shipped gradually over the course of a 5 month
> period, May-Sept, or an average of 104 butterflies shipped per month.
> So we are looking at roughly 208 total monarchs shipped by monarch breeders
> to the greater Minneapolis area (625 square miles) during August and September
> with a local monarch population of 62,500. So the released material would
> make up .03% of the local breeding population. This is substantially below the
> 1% - 5% or more fraction mentioned by Bruce Walsh. In reality, the fraction
> would be much. much lower than .03% since the southward fall migration in
> in the Minneapolis area begins in earnest on Aug. 24.
> My conclusion, based on this model is that the chance that monarch
> releases could disrupt the genetic structure of the local monarch breeding
> population in the Minneapolis area in late summer is negligible. It follows
> that the chance that a researcher might catch a released monarch when taking
> a random population sample is negligible.
> Pat, if you don't agree can you provide us with a reasonable model that
> demonstrates the validity of Dr. Karen Oberhauser's concern; i.e. that
> a modest amount of human assisted shipping of Maine monarchs to
> Minnesota (or vice versa) in late summer has a slight chance
> of disrupting the genetic structure of the recipient monarch population
> and could make it difficult for a researcher to study that structure?
> Best regards,
> Paul Cherubini
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