Re: Extinction (was Re: Fp. robertsoni)

[Wright Huntley <jwwiii at pacbell_net>]

Edd.Kray at rf_doe.gov wrote:

>  In keeping with my habit of questioning the "stylish wisdom  of the day",
> I ask:
> 
> Wright, you profess : "That means rigidly keeping different locations of
> the same species
> separate ". And how does this reconcile with the goal, of even the KCC for
> example, to maintain genetic diversity within our stock of a specific
> species? 


Genetic diversity, in species maintenance, means trying to *lose* as few as 
possible of the gene samples we received from the collector or subsequent 
breeders. We often start with a too-small sample, so technique can be pretty 
important to save what we do have. It is nice, but only rarely possible, to 
have infusions of new genes from new collections from that same location.

I like to start with at least three pairs, even if they were from a single 
pair earlier. That gives a really good chance of having most of the genes 
available that both original parents provided.

Gang spawning is great for species that don't kill each other. Swapping 
partners works as well, for those that do.

Our husbandry inevitably causes some selection, usually inadvertent, but 
sometimes deliberate. KCC tries to reduce that trend by having breeders 
exchange fish or eggs a couple of times a year.


> Aren't we then doing the same thing, e.g., inbreeding, that dog
> breeders have done for hundreds of years and  that has led to the
> concentration of recessive gene defects like hip displaysia in Shepards and
> Nards.  


Compared to those dogs, killifish are already incredibly inbred in nature. 
We are often surprised when a little subtle color variation shows up, 
because it is normally so unusual! Negative survival traits *can* be bred 
in, deliberately, as in the AKC insistence on a particular ring gait that 
favors loose weak hip joints. That has nothing whatsoever to do with genetic 
diversity or inbreeding.

We should try to avoid such negative selections, and attempt to not cause 
them by our breeding and keeping techniques.

> Don't we want to promote genetic diversity in our stock and
> wouldn't that be best done by mixing different locations of the same
> species? 


Genetic diversity has different meanings. I think we want to avoid losing 
any genes that were brought in from the wild, as much as is practical. The 
fish are usually so genetically identical that they might almost be clones. 
That's the normal result of filling a small niche environment -- the best 
genes for that environment win and displace all others.

> Isn't this why the australe, in the hobby for 50 years, is now
> runty and poorly colored vs wild stock ?


No. It is more likely lousy husbandry, and unfortunate selection, IMHO. 
[Harry Specht, who coordinates Aphyos for KCC may have a better input than I 
on this particular situation.]


> 
> I have this issue with my huberi strain.......As we have kept them in
> captivity for over 12 years (an "instant".... in the biological history of
> a species) , starting from the same wild strain and inbreeding them, I am
> seeing a gradual size reduction and a decrease in color and viability. I
> want some new genes but and am concerned that I would be mixing in a
> "different strain" from that originally sent to us by Bitter.  So I
> haven't. IS it better to let my aquarium strain die out, or to mix in genes
> from a slightly different locality? Tough decision for me.


If you really have an aquarium strain, why not go ahead and do it? You have 
nothing to lose. In the past, this has, once in a great while, resulted in 
gradual (or sudden) drop in fertility, if the cross was too different to 
sustain fertility. Usually, it causes a bit more variability, and that can 
let you select for what you like, such as bigger and more color.

It is those rare catastrophes that need to be kept out of any KCC-type 
program, for you may never recover from them. I recall the beautiful FIL 
Lagos commercially introduced about 1990-91 (by Sexton and Kiselev). It 
crashed after about 5-6 generations and nobody seemed to be able to keep it 
going. There probably was a female of a different species in that first 
batch. When you are trying to keep up genetic mix by gang-spawning and 
sharing stock, that kind of introduction is a disaster. It meant that the 
hybrids went out to everyone, and the strain was quickly lost.


> 
> Do we have a contradiction in principles in our breeding programs, the need
> for genetic diversity vs the desire to maintain our strains as distinct as
> they were from the wild? But then who is to say how distinct they were in
> the wild.Its the hobbyists guess.


AMEN! All we can do is the best we can figure out, and to share our 
experiences as best we can. Most of us in the larger clubs get to see many 
new wild fish introduced, so we can try to remember how they came in and 
attempt to keep them "natural," if living in a glass box eating flakes, 
brine shrimp, or blackworms is ever natural. :-)

Wright



-- 
Wright Huntley -- 650 843-1240 -- 866 Clara Dr. Palo Alto CA 94303

Ask of politicians the ends for which laws were originally designed, and 
they will answer that laws were designed as a protection for the poor and 
weak (...) but surely no pretence can be so ridiculous(...). -- Edmund 
Burke, A Vindication of Natural Society, 1756


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