In reply to Ron Coleman-
>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.
>
>Please reconsider.
I am rather surprised at your blaze of hostility here! I am not talking
about flooding the tropical aquarium trade with hybrids. I would however
like to see them produced under controlled conditions and then disposed of,
rather than traded. We're supposed to be interested in learning about our
fish, not just in making money from them.
In any case, the aquarium trade is infected with all kinds of hybrids coming
from fish farm production. But is interesting that they seem to be quite
limited in the species involved. In the UK, virtually all (non-wild caught)
Aulonocaras, Pseudotropheus, and Protomelas are not recognisable by me as
wild species. By contrast, all Melanochromis, Labeotropheus, Cynotilapia,
Labidochromis and Nimbochromis look clearly recognisable, although the
Labeotropheus & Cynotilapia cannot be assigned to particular geographic
races. I suspect some species hybridise and some dont. Also that the
particular species/race they hybridise with are not easy to predict. This
could shed a lot of light in speciaiton processes and comparison of Malawi,
Tanganyika, Victoria and neotropical species could be very instructive in
understanding relative speciation rates and mechanisms.
By producing these hybrids, as I suggest, the very worst that can happen is
that some unscrupulous individuals will release these into the aquarium
trade (not the wild!) and add to the immense numbers already circulating
anyway. I dont think such unethical people (who surely dont subscribe to
cichlid-l!) are going to be bothered conducting breeding for research anyway.
>Wait a minute, George!!!! There is no evidence that hybrid infertility
>has anything to do with speciation in the New World cichlids,
Indeed there's not. There's no evidence at all about what is responsible for
their speciation (apart from Midas cichlids & relatives and the Cuatro
Ciengas morphs, has anyone looked at anything to do with speciation in
neotropical cichlids?) and that's exactly the point. No-one is looking.
There is a lot of anecdotal stuff in the aquarist literature complaining
about how readily all kinds of cichlids hybridise in tanks, but virtually no
controlled experimentation nor systematic recording of what will hybridise
with what. Going from aquarist comments, I thought I could hybridise all
kinds of Malawi cichlids.
So far, on the basis of some very preliminary experiments, I am not getting
this impression at all. But the message coming through is that the bland
generalisation that all kinds of cichlids readily hybridise to produce
viable offspring is unscientific, anecdotal and quite possibly utterly wrong.
and the
>last thing we need is all sorts of new hybrids of cichlasomines or
>crenicichlas or geophagines floating around.
As I said I dont want them floating around either.
> I would even go out on a limb here and offer an answer to the
>question for all cichlasomines: any species will hybridize with any other to
>some extent. But say you found that C. spilurum wouldn't hybridize with
>C. umbriferum? So what? I don't think this tells you anything more than
>if they did hybridize since these species are vastly different in size and
>live hundreds of miles apart with many mountains, rivers and lakes in between.
I dont believe all cichlasomines will hybridise! And even if they do, it
doesnt answer all the other important questions I asked. What circumstances?
Viability? F2 breakdown. F1 unattractiveness to parental forms. All these
things make a big difference to our understanding of speciation processes.
Having recently dipped into the insect literature, I am shocked at how
absolutely ignorant we are about species isolating mechanisms in cichlids.
Indeed, its hardly possible to hold a worthwhile discussion with a serious
student of insect speciation, because it looks like we really haven't been
bothered doing anything much at all.
Ron talked about flooding the place with 'tons of dangerous fish'. Just what
is the danger? None to wild stocks or to properly maintained aquarium/lab
populations. Most serious researchers and lot of serious hobbyists deal in
wild-caught fish (or F1 from known & trusted sources). It's just dangerous
to stock circulating in the 'non-specialist' end of the aquarist trade. We
can't use these for taxonomy because of morphological plasticity. We can't
use them for hybridisation studies if Ron has his way.
So what's the point in mantaining purity? So we can say Cichlasoma xy spawn
in a clay flowerpot at 75-78 degrees F, males are bigger and brighter than
females and they thrive on a diet of beef heart and spinach (yawn)?
So, if these stocks are not going to be used to learn something useful about
the biology of the fish (like I have been suggesting) then why not just keep
all the nice bright hybrids to decorate your tanks! It would make lots of
people happy, just like all these nice Xiphophorus and Poecilia we can buy!
That hasn't stopped serious live-bearer fans from keeping stocks of pure
forms, nor has it stopped scientists doing fascinating research on these
genera.
George
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