<<
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.>>
I guess we need more research into this - is it because the hybrids don't
occur naturally in the wild because of such factors as preferred time of
the day to spawn; habitat preferences such as flowing water compared to
still water; preference to spawn in the tops of plants rather than on the
bases; preference to spawn earlier in the season when water temps are
cooler for one species etc etc. There are known examples of most of these
factors already.
I can think of a few mechanisms that would produce accidental hybrids in
the wild and these must occur regularly just by chance.to produce the
handful of recorded natural hybrid Rainbowfishes. Obviously, knowing that
the fertility of such crosses in aquaria is high, there are also survival
factors operating as well to limit or even exterminate these "unlike"
fry.I assume that as the water condition requirements are similar for
sympatric species that behavioural and predation factors are important
especially in these schooling species which after all are an important part
of the food chain for larger species including fish, birds, reptiles etc.I
would be interested if there is any work available on these smaller
schooling species and their survival as well as examples of them being
involved in translocation, competition with natural species, genetic
inter-mixing etc. To me it is possible that it is more of a worry in
Cichlids because of their territorial nature and predatory behaviour.
<<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.>>
So far the only example I know of for unsatisfactory survival in hybrids is
between Pseudomugils furcatus and conniae.
<<Also you could obviously have the same problems with introductions of
allopatrically occuring australian species into an area they were not
previously found.>>
Agreed, and the same safeguards for PNG species should apply to Australian
species from other regions.
<<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.>>
Good on you George - we need responsibility and safeguards. Bans just
encourage a black market and lack of compliance with regulations. It does
help to have examples to quote to both aquarists as well as authorities
when trying to reduce the emotion and increase the rationality in the
discussion.
<<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.>>
Especially to scientists :-)
Bruce Hansen
ANGFA
----------------------------------------------------------------------------
--------------------
<<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>>