What's a subspecies was: Species Concept Question

[Richard Pyle]

>      Well, I guess I just like making people scratch their heads
> and thinking harder about "testing" the status quo.

I don't mind testing the status quo if there is new information to challenge
old perspectives, but such is not the case in this complex.  As I said, the
"community" has been quite satisfied with the nomenclatural standing as it
is for 15 decades, the most recent 3 of which included full knowledge of the
hybrid situation.  Just because some naive young taxonomist with wide-eyed
enthusiasm for his own personal pet implementation of trinomials sees an
opportunity to nomenclaturally make his case, doesn't mean that he would
provide the taxonomic community any service by doing so.

> And that two
> populations of "flavissima" might have become xanthic morphs
> independently would make me even more (not less) tempted to put
> all these populations into one species.

Perhaps -- IF we had data to support that hypothesis, which we do not.  To
me, no new information translates to no new nomenclature.

> I would say that
> head-scratching is preferable to complacency, and I am really
> surprised that noone has formally proposed this, especially given
> that the ONLY known difference is color pattern.

Well, given that color pattern is the ONLY known difference between probably
hundreds of reef-fish species (lumpers and splitters tend to differ only in
how *much* consistent color difference is required to warrant recognition of
a nomenclatural species boundary) -- I think your desire to force people to
scratch their heads by disrupting the existing nomenclature "just because"
(i.e., with no new information about relationships or potential for gene
flow) would ultimately represent a significant DISservice to the taxonomic
and lay communities.

I'm all for head-scratching; and even for publishing un-supported,
off-the-wall, wacko, speculative ideas about possible evolutionary
affinities among morphotypes.  But I'm NOT in favor of using alterations of
Linnaean nomenclature as a vehicle to communicate these ideas. I believe
that stability of nomenclature needs to be respected more than it has been
in recent years.

>      Even to the non-specialist just interested in raising these
> fish in their aquarium, the fact that flavissima and vrolikii
> readily interbreed would be useful information.

Yes, and this information is widely known among the aquarium community.  In
fact, it was an article in an aquarium magazine that brought the hybrid
situation to the attention of scientists (Takeshita, G.Y. 1976. An angel
hybrid. Mar. Aquarist, 7(1): 27 35).  So the point is that the information
is already there.  I don't see a need to invoke nomenclatural change just to
reflect this one piece of information.  Perhaps with new data to show that,
for instance, vrolikii & flavissima are genetically identical (except for
whatever gene controls for xanthism) -- there would be compelling reason to
justify a nomenclatural change.

> It could have even
> inspired some breeding experiments in the 80's or 90's that may
> have challenged the "status quo" a long time ago.

...except for the fact that the first truly successful attempt to reproduce
species in this genus in captivity happened just this century.  So, even
though the information about the hybrid potential was very-much visible in
the 80's & 90's to inspire would-be propagators, the option was not
available (even now, only a couple of "blue-thumb" breeders have been
successful)

And yes, I have some captive breeding experiments in mind related to this
situation....but not for the angelfishes (we already know that they can and
do swap genes). The plot thickens:  As it happens, this same complex of
angelfishes is mimicked by the juveniles of a certain surgeonfish.  The
surgeonfish has historically been treated as a single species (Acanthurus
pyroferus), because the adults are essentially the same in all populations.
More recently, the surgeonfish was split into two species (A. tristis in the
Indian Ocean).

A. pyroferus
http://www2.bishopmuseum.org/PBS/images/JER/detail.asp?ID=-2072575067

A. tristis
http://www2.bishopmuseum.org/PBS/images/JER/detail.asp?ID=265165341

The juvenile mimics are uncanny (sorry, I have no online photos right now),
for each of the three "main" angelfish species in their respective regions.
I've seen photos of juveniles that mimic the hybrids in areas where the
hybrids dominate.

Now, here's the kicker:  Are the different surgeonfish juveniles
representative of different genetic populations? Or are they phenotypically
plastic, and somehow assess the dominant color morph wherever they settle
out, and develop coloration accordingly.  Alas, nobody has yet bred
surgeonfishes in captivity -- but I'd sure like to take parent stock from
one locality, and rear their progeny amid a tank full of angelfishes of a
different color morph.

Now, bringing this back to relevancy:  suppose we were able to demonstrate
that the differences in juvenile surgeonfish coloration are genetic, and
therefore likely the result of parallel evolution (classic mimic/model
phenomenon).  Do we then alter our nomenclature of the surgeonfishes so that
the nomenclatural splits correspond to those of the angelfishes?  To we bias
our nomenclature based on model/mimic relationships (how does it work for
similar situations in Lepidopteraland?)

>      In any case, I look forward to the results of molecular
> studies on these populations.  I wouldn't be surprised if the
> vrolikii population is the original mother population that has
> spun off two or more subspecies independently (i.e., that
> vrolikii is doubly or even triply paraphyletic).

My hunch (knowing the group fairly intimately), is that you're probably
right about that.

> If so, the
> sister to this whole grouping may show a color pattern more like
> the vrolikii population than to vrolikii's daughter populations.
> Only time will tell.

Not bloody likely, as no trace of any color characters in any species within
this complex show up in any other species in the genus.  It's going to take
molecular data just to figure out who the candidates are for the sister to
the whole complex is.

Actually, that's not exactly true:  There is one other all-yellow species in
this genus: C. heraldi

http://www2.bishopmuseum.org/PBS/images/JER/detail.asp?ID=-267642518

But for reasons that are too involved to describe here, I am quite certain
that the yellow of heraldi is independently convergent to that of
flavissima.

Aloha,
Rich

P.S. To peruse images of almost all species in the genus, go here:
http://www2.bishopmuseum.org/PBS/images/JER/images.asp?nm=centropyge&loc=&si
ze=t
But the dead-fish photos don't do the live buggers adequate justice!