The population biology of buttefly release
patfoley at csus.edu
Mon May 15 16:16:38 EDT 2000
Bruce and others,
The measure you propose is a good broad-stroke measure of genetic
differentiation over space. Low Fst species are plausible candidates for
release. But don't set the bar too low. Local populations of smallish size or
unknown genetic structure might make relatively little contribution to the
species Fst and yet be worth preserving intact for all of worries 1 through 4.
Would you release mainland North American Red Admirals (_Vanessa atalanta_)
in Hawaii? Presumably not since they are not native there, and the native
Hawaiian species (_Vanessa tameamea_ one of only two native butterflies!) is
fully reproductively isolated from the Red Admiral. Or is it? And even if it is
now, was it always? This is an extreme case, but consider that there are four
species of _Vanessa_ in North America that arose despite the famous wandering
tendencies of the clan and a presumably low Fst. Either this happened despite
constant migration (supporting some level of uncontrolled release) or geographic
isolation (or at least attenuation of gene flow) was required. We don't know!
Even in a poorly differentiated species, the increase of disease flow can
have disproportionate effects. In a highly differentiated population, the
potential for catastrophe seems high. But we don't know!
We still don't have a generally accepted theory that calculates the value of
peripherally isolated and semi-isolated populations for the evolutionary
potential, for disease resistance and for refuges against selfish DNA. Let's not
smear a species before we know it.
For the list as a whole, consider this hypothetical proposal that might come
close to a consensus between Bruce and me. No butterfly species should be
released in the wild without scientific reason until these criteria are met:
a) The species must have low population genetic differentiation (the level of
Fst to be worked out). Such data must be gathered and made publically available.
By whom? Where?
b) The butterfly can only be released in its studied range of low Fst. Some
serious solution to the problem of geographically unsuitable releases must be
developed before suitable releases are accepted because of the problems of poor
education and malice.
c) Some species of high long term scientific research may still be off limits.
Which are these?
d) The species considered for release need infectious disease monitoring. The
cost of this should be borne by whom?
Any other requirements? Or a complete rejection of the attempt at consensus?
patfoley at csus.edu
Bruce Walsh wrote:
> Let's try this for starters. Suppose the species of interest has a very
> low Fst (for the general reader, Fst= fraction of genetic variation do to
> between-, as opposed to within-, population differences), so that
> essentially all of the variation is between individuals, rather than between
> metapopulations. This implies that the population is really just a single
> strongly-connected population, so that historical gene flow has been strong.
> This negates your concerns 1-4, as levels of releases simply mimic the
> natural population-wide exchange that has occurred historically. For such
> species what are your concerns?
> The nice feature about the low Fst species that this is easy (and
> cost-effective) to check. A rule allowing releases into areas where the Fst
> values between source and release points are very close to zero seems
> reasonable and a first step that perhaps both sides can agree on.
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