RE: NANFA-L-- Re: Species questions

Peter Unmack (peter.lists at)
Mon, 14 Mar 2005 18:50:29 -0600 (CST)

On Mon, 14 Mar 2005, Crail, Todd wrote:

> But Dave, are the fish really sorting anything out... Or an extremely
> cynical view... are we just creating more arbitrary lines so we can stay
> in the lab, continue publishing and call ourselves successful, without
> having once gone outside? <evil_grin>

It's all about trying to make sense of natures great wealth of biotic
diversity. There are more than enough things out there to study without
anyone dreaming up imaginary stuff.

> Now I'm just playing devil's advocate here, with zero intention to
> ruffle feathers. But really, what is a species these days?

It is something that we can discriminate (hopefully via genes and
morphology) that is sufficiently different such that we can consider them
different evolutionary lineages.

> And has anyone made any kind of attempt-in-_breeding_ out across these
> clades to test if the geography holds up within the classic or even
> current definition of "species" after their revisionist descriptions are
> published? Would it be a real bugger if someone happened to collect
> both, randomly mix them, and then have the good Mr. Muller breed them
> out to F2's or F3's?

But what would that really mean? Many things we consider to be good
species interbreed and can produce viable offspring.

> I find it really hard to hold that there aren't "intergrades" or zero
> interaction in a single watershed inbetwix Ulocentrids (thus creating
> two separate species), no matter how different the geology is where
> they're found.

I'm not sure exactly what you are asking here, but I think I know. In
many cases I suspect that when two closely related allopatric species have
potential to intermix they probably do a little bit. Thus the lines are
usually a little blurry between many species. That is what would be called
a hybrid zone. These are probably far more common than people appreciate
as they can be difficult to demonstrate and document. My own work on
Australian rainbowfishes finds this to be the norm, not the exception.
This is normal, and does not suggest they are the same species, as once
you get a little distance away you see no evidence of introgression

> I mean really, I spent three days last week standing somewhere in
> between the edge of the basin, on the barrens, and-in-the base of the
> rim, and I'm not really sure where these "species" start and end, let
> alone where the physiogeography of these _streams_ starts and ends.

Sounds like a good phd to me! :-) If you are into species boundaries and
what prevents movement of genes across those boundaries. Fascinating
stuff me thinks.

Peter Unmack
Canadian River, Oklahoma
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