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Re: species maintenance (genetic thoughts)

>KI>I don't have the handout available, but a few years ago the (then current)
>KI>AKA conservation committee set up a program wherein a person would dedicate
>KI>20 tanks to one strain or species of killie. Four line were to be bred,
>KI>raised and after a few generations crossed. Something like 4 twenty gallon
>KI>tanks and a bunch of tens and a few smaller ones as breeding tanks were
>KI>suggested.
>KI>Possibly some of those interested in species maintenance backed off when
>KI>faced with those requirements. Most hobbyists either flat out don't
>have that much
>KI>tank space or if they do, don't want to tie up that much with just one
>KI>strain.

I wonder where they came up with this formula.  Clearly you want to
maintain as many individuals as possible and have them all breed.  This
seems like it'd do that, but there might be easier ways to get something
nearly as good.

>Good information and comments, Scott.
>
>But--what if we database who has what fish and dedicated aquarists
>arrange to trade stock? The individuals could get by with fewer
>dedicated tanks. This is exactly what zoos do to maintain diversity.[snip]
>And fish are a whole lot easier to ship than, say, a cheetah.

Actually, we probably wouldn't need a database, just a species exchange
listing section of the FEL, I'd think.  Those who are keeping a particular
species list what they need new stock for and exchange with whoever
answers.  Certainly this could be quite well encouraged.  That having been
said, though, I'm not sure what it'd get us.  As I understand it most
collections consist of a fairly small number of fish (not more than 10?)
from which all populations of that collection code are descended.  This
makes for a pretty serious bottleneck, and a few generations of inbreeding
among relatives should lead to most population strains being pretty inbred
at this point.  A bunch of the genetic diversity in that initial collection
would be lost quickly unless the number of keepers of a species is growing
exponentially.

Given that that is likely the case, it may be that all the lethal and
seriously hampering alleles (versions of genes) have already been selected
out in older strains, particularly in annuals (more generations).  Thus, it
may be likely that many of the deformities aren't from genetic problems,
but developmental miscues.


>Another area to look at is our culling procedures. I know, I know, it's
>hard to do, but it must be done for the health of the population. We
>obviously need to cull fish with deformities (bent spines, etc), but
>what about fish that are not fertile (but otherwise physically perfect),
>poor doers (compared to their more robust brethren), etc?

Fish that are poor doers cull themselves. However, they may also carry
beneficial alleles as well, so by operating under a stingent culling
regime, we are effectively reducing the genetic diversity that much more
severly each generation.  This isn't to advocate breeding "duds", but,
well, no, actually I think it *is* to advocate breeding duds, particularly
of species where the original populations are endangered.  To maintain as
much diversity as possible, you'd want to have every fish contribute
equally to subsequent generations (impossible).   By maintaining these fish
in aquaria, we select for fish that are pretty in aquaria, but are probably
losing traits which are valuable in the wild, even if they aren't expressed
(as not all genes are).  By reducing the number of parents who give rise to
each successive generation we increase the chance that beneficial (but
silent) genes are lost.  For example, any traits that may assist in
predator evasion are irrelevant in our tanks, and so may get lost.

It seems that the aims of keeping fish and maintaining genetically diverse
species don't always line up exactly.  I think that in the interests of
both though we could:

1) do more fish exchanges
2) not cull too stringently.  This may lead to more dull fish, but if there
are thoughts of reintroducing fish from these extraordinarily maintained
resource it might be worthwhile for some to dedicate some space to
maintaining less desirable fish, too.
	 As a newbie killie keeper, but a population geneticist I'm struck
with the amazing efforts to maintain these species.  If you were to set out
to design a system for maintaining genetic reserves using a diffuse set up,
I think what we have is pretty much what you'd aim for.  From a scientific
standpoint it strikes me a bit like the biological equivalent of
SETI-at-home.  It occurs to me that one could probably maintain a lot of
plant diversity by tapping into the networks of gardeners that already
exist.


Anyway, back to work!


Doug


Doug Karpa Wilson

Department of Biology
Jordan Hall
Indiana University
Bloomington, IN 47405


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