> 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