Hello Dan, thanks for your reply.
The "single pair" model is valid provided that neither of the pair hybridise
with the locals - the available evidence suggests that this is unlikely.
Apart from any ethical/conservation considerations this whole business is about
the "selfish" desire of some aquarists (including myself) to keep good looking
New Guinean fish, be they new species or just better specimens of what we
already have. I belive that this motivation is an acceptable one and that
people should not be ashamed to say "I keep these fish because I like them"
without having to harp on the preservation angle. The conservation of the
Australian wild fish is very important too. There must be a balance reached
between the two - I cannot believe for one moment that the number and variety of
(for example) Cichlids entering Australia legally are any less danger to native
waterways than a few Rainbowfish...
And as for the kooks, well, we have some of those here on both sides of the
argument ;)
Regards, Andrew
______________________________ Reply Separator _________________________________
Subject: Re: Re[2]: [RML] Re: Hybrid ethics-
Author: PC:dd at dandrake.com at INTERNET-MAIL
Date: 2/10/98 8:53 AM
In <199802042215.JAA08417 at tor.dfat.gov.au>, on 02/05/98
at 09:21 AM, andrew.boyd at dfat.gov.au said:
> Yep, makes sense now... population stats begin to enter the realm of
> Chaos maths, which I will not get to study but the Mem tells me are
> lots of fun. ;)
>
> Is there a general formula for the spread of exotics?
>
No, but you're sure right about the chaos. In addition to what Bjorn said
about a larger initial population being in less danger of a sudden
wipeout, consider genetic diversity. A single pair might survive and breed
weakly, generating a tiny population that survives a few generation till
some disaster (from their point of view) destroys it. Another pair or
two, introduced before the first population dies out, _might_ put an end
to the inbreeding and introduce a new mix of traits that will allow the
population to expand.
The extinction of various genes within a small population is a completely
chancy process, as is the establishment of undesirable ones. So the
survival a new little population depends on chancy genetic drift as well
as storms and droughts and whatnot.
I guess epidemiology has some good formulas for the spread of things, but
for all the reasons given, they're unlikely to be good for specific
predictions.
A couple of examples of spread of introduced species. 100 yards from here
is one of the most ecologically polluted bodies of water anywhere. Ships
have been coming into San Francisco Bay for 150 years and dumping their
ballast water full of illegal alien nasties (quite apart from all the
deliberated introductions) but the level of destruction of native species
is now shockingly bad. Anyway, it's shocking some people. OTOH a mile to
the east of the bay, on the UC Berekley campus, there's a small colony of
a Mediterranean weed that has been in the same spot for 100 years (IIRC)
and has never spread from there. No one really knows why.
At least this list doesn't have people arguing that it's genocidal elitism
to deny the introduced species their right to live where they want. Does
my beloved California remain the world capital of kookdom, or can you
Aussies top that one?
--
Dan Drake
dd at dandrake.com
http://www.dandrake.com/index.html
Many things are not seen in their true nature and as they really are,
unless they are seen as beautiful. Behavior is not intelligible, does
not account for itself to the mind, and show the reason for its
existing, unless it is beautiful.
--Matthew Arnold