----------
> From: peter.unmack at ASU.Edu
> To: rainbowfish at pcug.org.au
> Subject: Re: [RML] RE: Re: M. herbertaxelrodi/trifasciata
> Date: Monday, December 16, 1996 3:05 PM
>
> On Sun, 15 Dec 1996, Roy Hunter wrote:
>
> > Seeing how we are talking millions of years here in evoloution why is
there
> > a seperation of species between fish like rubrostriata/inorata
>
> These two are the same species, they only differ at the subspecies
> level. It is a somewhat arbitrary split, there is at least one inornata
> around Weipa that looks just like a rubrostriata.
>
> > goldei/trifasciata
> > oktediensis/trifasciata there are common fish within sahul such as
werneri
> > and gertrudae but rainbow wise there is little else..(common as in the
same
> > fish found in both land masses like werneri)
>
> Species don't neccessarily diverge at similar rates. As Harro pointed
> out, lungfish have changed little in over 100 million years, at least
> osteologically (bone stucture). Perhaps those we don't consider
> different today (gertrudae etc) really are different, or perhaps some of
> those we consider different are not. We cannot assume that the present
> taxonomy is correct (although it appears to be pretty right based on
> currect technology). It is largely based upon opinion. Also depends
> upon how one defines a species. It appears obvious that gertrudae has
> undergone divergence sometime in the past as paskai would appear to be a
> sister species to it. You can get repeated invasions, some of which
> persist or change, some of which don't.
>
> > correct me if I am wrong but
> > the two masses were joined 15,000 to 10,000 year ago durring the last
ice
> > age.
>
> That is true and also many times in the past as sea levels went up and
> down many times.
>
> > That does not seem to be ample time for the changes to constitute a
> > new species. If it is then there should be greater differences in the
fish
> > found in oz that are widespread like Trifasciata's.
>
> Except that you forget that there has been potential mixing (refering
> to the lake that existed in the Gulf of Carpentaria) between
> populations that can blot out any divergence that may have occurred.
> That's the thing, unless these things evolve reproductive mechanisms to
> isolate them they will all mix in together and differences will be merged
> and lost.
>
> > those populations have "crossed" within the last 15,000 years, and
there
> > are a lot of body differences in them.
>
> Body differences, especially in many (but not all) rainbows is pretty
> meaningless IMO. This is a highly plastic trait. All this means is
> that there is substantial variation in the phenotype caused by
> environmental effects. It is very easy in captivity to produce deep
> round fish and slender fish from the same batch of eggs raised under
> different conditions.
>
> > What makes rubrostriata a seperate
> > species from an inornata? obviously there is one and why do differences
in
> > inornata's not exist within OZ. well maybe tati could be an example but
you
> > get the impression that species differences are geographical. ie no
>
> Again, these are all the same species. There tends not to be distinct
> boundaries between subspecies, meaning that there is a gradual change
> from one form to another.
>
> > Chalitherina's or Glossolepis in oz nor any Trifasciata's, splendida's,
in
> > New Guinea....
>
> Aren't all the Glossolepis and most Chilatherina's found north of the
> dividing range in New Guinea? I don't have my book handy. That mountain
> range is a major barrier to dispersal and a very effective isolating
> mechanism. It may well be that an ancestral Melanotaeniidae made it into
> northern NG before the mountains were as high and due to the long time
> period slowly diverged into what we see today. Perhaps both represent
> seperate invaders by two different ancestral fish at different times.
> Aren't most of the Melanotaenia found south of the dividing range too? I
> know there is at least one north of it, but most are south. Why are
> there no tris in NG is a good question, same as why aren't spangled
> perch there? It doesn't make sense but it is real.
>
> > My Mail program adds the previous message..just deal with it :-)
>
> Then why don't you just learn how to use your email package. These
> things can normally be switched on and off. You computerphobe. Sure
> you have a degree in computers? :-)
>
> Tootles
>
> Peter Unmack