I don't think anyone would expect an individual would be able to single
handedly maintain the genetic diversity of a species (unlesss that
species in homozygous and monomorphic), let alone a few species. It
requires a group effort between different aquarists and/or
institutions. I get the impression from some people who read
publications such as the ACN's Captive Maintenance Guidelines that it is
expected that one aquarist will be able to do everything. It can't be
done that way. It must be a co-ordinated group effort.
> figuring out the numbers of fishes involved in attempting to maintain a
> certain level of genetic diversity over a long period of time; the results
> were staggering. It seems to me that most people who were trying to maintain
> a species would either end up doing too much inbreeding, or would swap with
> only a couple of other aquarists, effectively creating one population pool
> which would in itself be subject to too much inbreeding fairly soon as well.
Inbreeding is not neccessarily bad for all species. Some fish species
such as the Devil's Hole pupfish appear to have relatively low
heterozygosity (within individual genetic diversity) and polymorphism
(within population genetic diversity). This is the result of the fact
that they have been inbreeding in a small population size for 10s of
thousands of years with no obvious known ill effects.
Further to that, according to genetic theory it is possible to inbreed a
number of seperate lines of a species over a number of generations, then
outcross the lines and restore the original variation (or at least close
to it). I would image that for some species this may work, for others it
may not work at all. It just depends upon the target species and the
only way to find out is to try it and monitor the results.
> In my reading, one of the most effective techniques in maintaining
> diversity seemed to be in equalizing family size
It is important to have an equal contribution by both sexes to the next
generation. ie, if you only have a single male about half the
contribution to the next generation comes from only one fish no matter
how many females you mate with him. If you have two males then it
should be closer to one quarter each.
Ooroo
Peter