RE: Further thoughts on SMP

["David W. Ranney" <dranney@alvord.k12.ca.us>]

Richard wrote:

>>Sure, there are anecdotes like this, but this was pure chance.  There is no
>>evidence that such a situation would have the same result with fish or any
>>other organism.  In fact, I can think of other anecdotes from the aquarium
>>hobby in which the abililty to breed certain aquarium strains became
>>increasingly difficult from generation to generation, most likely due to
>>effects of inbreeding.  
>
>While I appreciate your dialog, your third sentence above is very
>misleading and highly inaccurate when you consider the selective
>genetics of the guppy, swordtail, platy, betta, and molly. And I
>disagree with it based on genetic and personal experience.

I think you mean my second sentence.  I can see how this statement can be
easily contradicted by the evidence you present.  However, what I meant to
say (forgive me for not being clear) is that there is no _guarantee_ that
line breeding will be "beneficial" or benign for any given species.  For
example, many killifish keepers have been complaining about low fecundity
in some strains of Aphyosemion australe gold (the orange lyretail), a morph
that has been line bred for quite a long time (perhaps 30 years or more).
This fish was considered extremely easy to breed in the past.

>While fish in streams, rivers, ponds, and lakes have the ability to
>travel, most remain relatively in the same general area, thereby
>reducing their genetic diversity  by not traveling to somewhere else in
>the area, i.e., 20 miles downstream. If collections are done along a
>stretch of a river for the same species, there is some genetic drift as
>isolated pockets do develop--that's what happens in the hobby as well.
>But where do you draw the line of what is a species, what is acceptable
>for maintenance as opposed to maintenance of every conceivable 'genetic
>drift' combination you might find? I don't have an answer to that.

Correct, many populations of a species may be quite isolated from the
others.  And, genetic drift may occur, but will only be significant if a
population is relatively small.  However, when there are several different
populations of the same species, separate enough to drift genetically from
one another, the occasional migrant between populations can be extremely
important for both within-population and total-species genetic diversity.
In such a species, this rare immigrant could be a large factor in
preventing increased homozygosity and associated inbreeding depression.
While this statement is based mostly on theoretical results (including my
own), we do not have enough empirical data to say whether or not this
effect is important in living organisms (it would be a big job to measure
migration rates between populations of Apistos!).  So I would say that it's
best to be on the safe side, and attempt to preserve as much genetic
diversity as possible.  Of course, not knowing the "natural" rates of
migration between populations makes it impossible to suggest a satisfactory
rate of crossing between aquarium populations (if any such crossing should
be carried out at all).

As to your last question, I would say that if we're interested in
preserving a species in the aquarium hobby as it is in the wild, we should
try to keep representative populations from as large a portion of a
species' range as possible.  "Where to draw the line," while not
straightforward, shouldn't be too difficult a decision.  However, if one of
the goals of a SMP is to preserve a good portion of a species' total
genetic diversity, I would suggest the following program:  Keep populations
of a species separate in aquariums, but attempt to keep as much genetic
diversity within populations as possible by not culling too severely and
infusing the aquarium population with "new blood" from the wild populations
whenever possible (as Steve originally suggested).  It would even be
possible (although a logistical challenge) to keep track of an "effective
aquarium population size" for each population, if one had lots of free time
on his hands.

>fish in the future. The problem is, of course, each individual's
>interest, limited resources, and perception of the need. It would only

Very true.  I would bet that most aquarists, while generally supportive of
conservation efforts, mostly just want beautiful fish for their aquariums,
and aren't too concerned with their fish's genetic background.  Now that I
think about it, my comment above about "effective aquarium population size"
seems like sheer lunacy. ;)

Julio wrote:

>I think the SMP can accommodate both. Categories that separate "species",
>"aquarium strains", and "populations" will play an important role here. The
>first two categories will deal with the hobby while the "population"
>category can cover conservation of wild populations. 

I agree wholeheartedly.  So long as the members of a SMP keep things
separate, they will be carrying out an interesting experiment no matter
what they do.  Then, using their results, they can refine their program.

- -Dave

- -David Ranney
- -dranney@alvord.k12.ca.us
- -Science Teacher, Technology Coordinator
- -Wells Intermediate School
- -(909) 351-9241