> << the main reason for many of the
> species that're closely related not hybridizing is that there are either
> _geographical_, behavioral, or structural differences that prevent it.>>
>
> That's the general explanation as I recall it.
So Bruce, exactly how do 3 or 4 rainbowfish manage to live in sympatry?
I would think that the answers to that question would be important to
know before generalising that adding a further species wouldn't cause any
problems. I'm not talking generally either.
> This is the nub of it all Julie - if I had said that peter would have
> said' "Who says it's the same with bows, where's the evidence?"
That doesn't make anything right or wrong and it is irrelevant in this
arguement. :-) And, actually, I probably wouldn't have said that unless
I wanted to get a rise out of Bruce.... :-) ;-)
> 'proper" conditions for translocation ( improper may be more appropriate).
> How likely is it? would youlike to put a numerical risk assessment on it? I
> believe the scientists who are advising the bureaucrats
> on this very risk should be putting a relative risk estimate against
> each of these species and this should be assessed against an agreed
> threshold loke they do for most things when designing policy - the
> so-called relative risk for each.
Last I heard from Bryan Pierce there was a system similar to what you
describe being developed or proposed. I have no idea of its present status.
> As I said before PNG fish have been here
> in Queensland for 20 years, and bred in outside ponds in cyclone areas with
> monsoons every year and how many examples have we found of Bows being
> "naughty"? Now if the scientists need some evidence how about that? How
> many years does the trial need to go on for?
Who has ever been back to sample the local rainbow populations and how
would you detect it in the absense of data before any potential
introductions (in the case of translocated natives of the same species or
closely related ones). That is part of the reason why many people are
cautious. I remember hearing about someone breeding mass rainbows around
Rockhampton outside which was flooded back around 1993 during a cyclone.
Has anyone ever tried looking in that area since then? I'll bet not.
> But there are many instances in Australia ( and PNG) where 2,3, 4 species
> co-exist and do NOT show evidence of crossing except as an exceptionally
> rare event. I submit that as a natural example of there not being a problem
> with this group as long as the habitat is in good shape.
It's not so much a question of good habitat, but whether they have
evolved in sympatry or allopatry. I'll bet you'll find differences
between allopatric and sympatric populations of the same rainbowfish species.
> Competition can do this IF the "invader" has a significant biological
> advantage e.g. bigger teeth, nastier disposition, viviparous (avoiding the
> vulnerable egg stage) etc etc. However I contend that most bows are very
> similar in general temperament, diet , longevity, ecology etc and the
> differences (mainly due to geographic isolation ? and subsequent evolution)
> do not constitute a significant competetive edge. Consequently I contend
> further that even in the UNLIKELY event of a viable population becoming
> established that there would simply be another species of rainbowfish
> co-existing with the previously present ones.
You are assuming that nothing else in the environment exists other than
rainbowfish!!! You are also focused too tightly on the hybridization
side of things too.
> I would accordingly have
> thought that the Lake T Cichl;ids were more comparable than a schooling
> group like Rainbows. Now that I come to mention it , perhaps Peter can
> dredge up some examples of this problem in Tetras. Danios, Rasboras etc
> some where in Africa, Asia or South America? It seems to me that this may
> be a good direction to look.
A good suggestion, however, I don't know the literature THAT well! Also,
few studies have been conducted on these type of fish in their native
habitats. I'll have a think about it thought and ask around a bit.
> PS Lecture away! I would like this thread to end up with some concrete
> direction eventually. That doesn't mean that we will change any of the
> facts but maybe we will all understand the issues better and the risks
> (both qualitative and quantitative).
Fully agreed. Perhaps after such a lenghty discussion someone would
volunter to come up with a brief crude summary of the issues and
disagreements in order to try and clarify further points of discussion. I
don't have the time myself.
Peter Hughes has gone rather quiet. :-) Bet you weren't expecting this
much fuss! Everyone else seems to have chickened out too except a couple
of us. Are we just wasting our time? I think if we REALLY cared about
our native fish we would be interested in whether translocating rainbows
is a problem (of which some rainbows are--more so local translocations as
previously discussed--if you really disagree that moving Gin Gins to
the Brisbane River would be a problem please speak up and add some
evidence for your belief--I do agree though, that not all rainbows are
likely to be a problem). I don't see any of those folks doing much to
try to educate other less educated folks. Or do we just expect the
government to educate us all? At least I'm still here having my own
beliefs and thoughts challenged.
Cheers
Peter Unmack