>> 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.
I couldn't stand longer. Sorry, Peter. This isn't obvious for every
scientist. According to some more recent publication of Mayr (the
grandfather of the modern species concept, I think he still lives
but must be about 90 years old now) a subspecies necessarily
requires a hybridization zone. On this subspecies concept you
can also read in publications of Rosen on Xiphophorus from Guatemala
and Mees on Dysichthys (banjo catfishes).
According to this view rubrostriata could also have species rank.
>> 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.
That's the old point, we haven't been there watching it. Everything must
by hypothetically.
>> 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.
To my opinion 15,000 years may be long enough to evolve the tri varieties.
>> 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.
See above, you may see it different.
>> 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.
It should make sense as it may tell us about common ancestors and
try to help get clearness into relations of rainbows. However, that's
a longer answer, will come later.
One other thing Roy started when he asked if the common ancestor of
rainbows and maybe related fish could be found. The most popular
concept in time terms of evolution is the chronospecies concept.
That means (in short words) that a species has to be named new
if you can proove that a new one evolved from it. Under these
circumstances there can't be a species named as ancestor species.
However, as Peter already wrote, the first rainbow will have looked
different from all what we know today with a nearly 100% chance.
Harro