>On 4 Feb 97 at 10:11, Ron Coleman wrote:
>>....
>> I DON'T THINK A CALL FOR WIDESPREAD HYBRIDIZATION EXPERIMENTS IS
>> EITHER WARRANTED NOR RESPONSIBLE.
>>
>> Perhaps certain crosses are of interest and value, notably
>> particular species in say Lake Malawi, but many other crosses will
>> lead to tons of dangerous fish and no useful information. ....
>
> Though I'm sure Mr. Turner was not trying to encourage damaging
>hybrid proliferation, I support Ron Coleman's position. Only with
>strong and constant action against certain current beliefs on the
>acceptableness of hybridization, do we have any chance of stopping
>the worldwide spread of hybrid genetics.
I agree that pollution of natural genetic stocks by hybridisation is an
extremely important issue in biodiversity conservation. I also agree with
Kelly's view that scientific environmental impact studies and assessments of
'small probabilities', 'likelihoods' etc are in fact usually biased and
untrustworthy. Many scientists carry out superficial and largely irrelevant
research and come up with conclusions designed not to offend funding
agencies or potential sponsors. This is indeed a consequence of short-term
fund-chasing attitudes and is not something to be swept under the table or
excluded from serious discussion by practising scientists. It has the
potential to destroy public trust in the objectivity and honesty of
scientists and is of the greatest importance. The eventual result of this
trend will be that if no-one trusts our findings, why should anyone fund us
anyway? It is a big issue though, and the only thing to be done (apart from
trying to restrain our ambition and greed) is to hope that someday there may
be a return to the old system where scientists were employed on life-long
contracts and were able to fund their own research directly from their own
institutional funds without having to go grovelling after business and
government agencies. It used to be called academic freedom, according my
history books.
> I'd like to support Ron Coleman's request that we not encourage
>non-scientists to hybridize without close scientific supervision.
>Hybridization is very common already. It pollutes the aquarium
>trade. It does risk wild populations in the long term (I don't have
>time to explain this and if you think environmentalists are generally
>extremist you would not grasp (believe) my explanation anyway). The
>encouragement would spread beyond Cichlid-L and be used to support
>`'bad'' behaviour by others. The descendants of some of these
>experiments would spread throughout the world.
Having agreed with Kelly's overall position, I would like to make several
things clear about my suggestions about hybrid studies-
1. Most of the experiments I propose would be done in countries which have
no native cichlids at all (ie. all europe & australasia, most of north
america and asia), so releases into the wild wont lead to damage to wild
populations.
2. I dont want anyone to release them into the wild
3. Hybrids are being produced on an immense scale by the aquarium trade as
previous replies have clearly demonstrated, so production for knowledge
rather than profit will be of minor impact
4. If hybrids escape into the wild in areas where there are indigenous
cichlids this could lead to introgression with wild stocks. However, if
cichlids of different species hybridise so easily (as most of the replies
suggest) then introduction of NON-HYBRIDS into areas where they are not
indigenous will have exactly the same effect! For example if C.meeki and
C.nigrofasciatum are found allopatrically in the wild, introduction of
C.meeki x C.nigrofasciatum hybirds into the range of C.meeki could lead to
loss of genetic integrity of wild C.meeki populations, but so would
introduction of pure-bred C.nigrofasciatum or indeed pure-bred C.meeki from
different parts of its native range. The only solution to avoid this would
be to ban the aquarium trade altogether.
5. I can think of one rare exception to the point I made in section 4. If
two species co-exist in the wild without hybridising, it is possible that
they will hybridise in lab conditions (e.g. when deprived of conspecific
mates). The hybrids if released into the wild might then be acceptable mates
for BOTH wild pure species and this could then lead to them introgressing.
This is a genuine danger. A case in point is that Oreochromis karongae and
O.shiranus have hybridised in aquaculture ponds (nothing to do with aquarium
trade or research, but to feed crocodiles in a croc farm!) in Malawi right
next to the main lake where they co-exist. If such hybrids are fertile and
viable (and we dont know this, because no-one has done it under controlled
conditions- LIKE I'VE BEEN SUGGESTING!) then this could lead to a disaster
for the wild populations. This is going on all the time, and has nothing to
do with the research I am proposing.
On Peter Unmack's earlier point about rainbow fishes and why alien species
might prove more of a problem than native ones-
any 2 species that naturally co-exist in the wild must by definition be able
to co-exist without loss of genetic integrity of the species - of course
there could be some natural hybridisation, but it cant have much effect on
the independent genotypes, since these continue to co-exist.
With allopatric forms you have no such guarantee at all. Australian and New
Guinean forms may not be reproductively isolated from one another. They may
in fact be unique subspecies (assuming a biological species concept) which
would readily cross if they were not geographically isolated. If you placed
males of one species with females of the other (and vice versa) and they
could not produce viable and fertile hybrids in the lab, they could not do
so in the field either and thus you would know they could not hybridise with
each other even if released. Of course, it is quite possible that the alien
species could simply exterminate the native ones through outcompeting them.
However, at least this is potentially reversible, since you could try to
exterminate or control the competitively superior species or preserve the
native species in captivity. With introgressive hybridisation its too late
as soon as it starts.
Also you could obviously have the same problems with introductions of
allopatrically occuring australian species into an area they were not
previously found.
Would I support a ban on the import of rainbow fishes into Australia? Dont
know. Seems like a small risk in comparison to the risks of pollution,
introduced salmonids etc. It is of course essential that aquarists behave
responsibly and try to minimise escapes. A ban on pond breeding might be
appropriate.
Anyway this is all rather beside the original point, which is that
artificial hybridisation of cichlids in tanks in areas where they are not
native is useful and harmless.
George Turner
Dr G.F.Turner
Lecturer in Ecology/ Biodiversity
Division of Biodiversity & Ecology
University of Southampton
Bassett Crescent East
SOUTHAMPTON SO16 7PX
England, UK
Phone- 44-(0)1703 594394
Fax- 44- (0) 1703 594269
e-mail gft at soton.ac.uk