Subject: Re: NANFA-L-- two interesting articles
From: Peter Unmack (peter.lists at)
Date: Wed Oct 20 2004 - 15:29:49 CDT
On Wed, 20 Oct 2004, Todd D. Crail wrote:
Again, I'd like to caution making strong arguements about heterozygosity
and fitness (especially relative to your comments on Gambusia below). I
just don't think they are realistic. They sound really good in theory,
but there is no hard evidence to support this idea. The big problem is
that we don't really know what causes some species to do well irrespective
of bottlenecks or smaller population sizes versus others who suffer badly
with inbreeding. It probably isn't gross heterozygosity per se (although
it could be heterozygosity at specific loci, in other cases it could be
too much heterozygosity if some of that variation is deleterious). I
think the only thing you can take from this is to try and mimic the
breeding system of a given species of interest to they way the do it in
the wild. What that means for example is if a species often colonizes
waterbodies with a small initial starting population then inbreeding will
not be as bad as compared to a species which spawns in large groups
allowing for lots of mixing of gametes. And of course, that would only be
a guideline, I'm sure plenty of exceptions to that exist as well.
On a different subject, there were some cool articles in the latest issue
of nature on vertebrate genomes after a large proportion of the second
tetradontiform (puffer fish) genome was recently completed. The link I
get is
http://www.nature.com/cgi-taf/dynapage.taf?file=/nature/journal/v431/n7011/index.html
but that might not work for all, just go back to nature.com and the latest
issue should be listed near the top left corner. Well worth a read if you
can access it.
Cheers
Peter
> So in this case of the carp, enough of the necessary heterozygous traits of
> the genome were present with that population (do a websearch on "Hardy
> Weinberg") to make it through the bottleneck of stocked ponds, work on the
> bottleneck of the wild and begin competing with natural selective forces.
> On the other side of this... In the case of gambusia, for example... I would
> suspect that the genome of the species is _incredibly_ heterozygous (have
> the genetic briefcase to cover a wide array of factors and be successful) to
> deal with what may be a very ephemeral habitat and very limited individuals
> as a initial population. Like they carry the "super genome" with all sorts
> of survival tricks in a single individual instead of having them distributed
> across a whole population. I'd be interested to know if anyone can shed
> factual light on this... I could be completely wrong, but I think this is a
> valid argument to explore if it hasn't been (I'm pretty sure it has though
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: Fri Dec 31 2004 - 11:27:51 CST