Butterfly releases redux

[Patrick Foley]

Bruce Walsh is right about most things, but leaves some important points 
out, most of which have been made previously on this list.

1) A small amount of migration (equivalent to one individual per 
locality per generation) is sufficient to smear out genetic variability 
due to neutral alleles.

2) Some methods for studying migration depend on frequencies of _rare_ 
alleles (see Monty Slatkin's work).

3) Rare alleles, rare bits of DNA, rare microorganisms, rarely 
transmitted, can all be of great global consequence if they can 
reproduce and if natural selection (even in some perverted form- Nature 
is not watching out for us or butterflies- Nature favors the bigger 
broods) is in their favor. This is why as some here have pointed out, 
diseases are best left untransmitted (from the host's standpoint). And 
the same applies to transposons, genes that produce runaway sexual 
traits and other runaway genes causing as yet unstudied problems.

4) There is little direct evidence either way about the harm done to 
populations or metapopulations of butterflies by increasing rates of 
migration. There is general theory on epidemiology that shows that it 
all depends on the disease, the migration rates, the distribution of 
alternative host and the fatality of the disease although for the 
typical vertebrate with serious of conservation interest, migration 
seems to be a plus (see Hamish McCallum and Andy Dobson 2002. Disease, 
habitat fragmentation and conservation. Proceedings of the Royal Society 
of London B 269:2041-2049.). It would be great if the USDA (who 
regulates butterfly releases) would fund some work on the problem, and 
if the population biologists, epidemiologists and population geneticists 
among us would do the work. But so far as I know, it is not being done. 
When, inevitably, you are told that some butterfly breeder has done 
something to show that releases are ok, you might want to examine the 
study carefully, look to see how well reviewed it was and so forth.

5) Our experience with released micro- and macroorganisms is extensive, 
sometimes benign (from human standpoint) and often disastrous (see the 
literature on classical biological control). Why should the widespread 
release of microrganisms and potentially runaway genes (which inevitably 
accompany the release of a butterfly) be any better?

6) Maybe the issue is moot with Monarchs and Painted Ladies since 
releases already occur and because they are so migratory and 
cosmopolitan already. But even with this wandering nature, new species 
have managed to evolve in their clades (suggesting geographic isolation 
occurred before human interference).

7) Maybe the issue is hardly worth fighting over (compared to crusading 
against Islam or Global Warming). But that does not change the risk to 
the butterflies or to our scientific credibility as we debate the issue. 
So let's try to get the facts and theory straight, rather than attack 
each other on ideological grounds.

Patrick Foley
patfoley at csus.edu


jbwalsh at email.arizona.edu wrote:

>Xii and Stan have brought up Kimura's neutral theory. In particular, Xi notes
>that
>
>
>
>      "For mutations which cause an obvious and significant change in phenotype,
>
>      it is still natural selection that is mainly responsible for fixing
>it (or
>
>      not fixing it). "
>
>
>
>Actually, since must mutations are introduced as a single copy, the chance
>
>of it getting fixed under drift is 1/(2N) where N is the population size.
>
>If a mutation is such that individuals carrying it have a fitness advantage
>
>of s, then the probability of fixation from a single copy is bounded above
>
>by 2s. While this probability is greater than 1/(2N), the punch line is
>
>that most favorable new mutations are lost by drift during their first few
>
>generations of existence.
>
>
>
>For those interested, see lectures 42 - 45 for the population genetics background
>
>and lecture 46 on the neutral theory at:
>
>
>
> http://nitro.biosci.arizona.edu/courses/EEB320/EEB320.html
>
>
>
>Likewise, if you are very perverse and want to see all the gory mathematical
>details, see chapters 14 - 17 at
>
>http://nitro.biosci.arizona.edu/zbook/volume_2/vol2.html
>
>
>
>Cheers
>
>
>
>Bruce
>
>
> 
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