Species Concept Question

[Richard Pyle]

> This is exactly why I have difficulty with an absolutist approach to the
> species (i.e. the world can be completely divided up into nice neat
> units). I put forward a very similar argument in my PhD thesis in the
> mid 1990's about this. If I can find an electronic copy of it I will
> send it to you off list.

Thanks!  I'd like to see it.  We are clearly very-much in agreement on this!

> I see no way of choosing between the nomenclatural options you suggest.

I see no *objective* way of choosing; but I was hoping to get a sense from
the taxonomic community at large whether there is a *subjective* tendency to
call them separate species, or conspecifics, or invoke the subspecies rank.
So far, the few replies I've received have leaned toward separate species
epithets with the acknowledgement of a hybrid zone; or perhaps a trinomial
solution to emphasize both the apparent close relationship, and the

> What is more I see no way of knowing that the two extreme taxa are
> sisters if you include the 'middle' taxa in your analysis. Inclusion of
> your hybrid swarm in the analysis would cause the clade to collapse to a
> bush.

Again, no purely *objective* way of knowing (strictly speaking, there is
essentially *no* way of "knowing" in any case; but I'll assume that
"knowing" is more or less defined here as "arriving at an extremely
convincing conclusion").  But if we embrace a more subjective approach to
nomenclatural application, we might find that communication among biologists
is ultimately enhanced.

To be fair to the cladistc view, however, one could establish that the
entire scope of populations (X, O, and putative hybrids) represent a
monophyletic clade with respect to all other populations, and thereby
establish "sisterhood" of a dichotomous pair of populations within the
entire group.  But this is weakened by the method to establish
"dichotomous", when confronted with a hybrid swarm.  In my Pattern 1; you
could certainly establish "bimodal" as a surrogate to "dichotomous"; but you
might be harder-pressed to do so in my Pattern 2.

> But you can't know you have a hybrid until you have defined your
> taxa. But you can't define your taxa until you have eliminated your
> hybrids and done a phylogeny. (cf Heller, J. 1961)  This is the nub of
> the problem of why taxonomy is floundering. We can legitimately go round
> and round in circles and there is no 'correct' answer. The best way to
> describe the diversity is to choose one nomenclatural solution (any one)
> and put notes in the margin as to what the relationships might be. This
> means that for a significant proportion of diversity what we call things
> is going to be more or less arbitrary.  Most taxonomists don't like to
> think like this though.

I guess I'm an exception among taxonomisist, because this is *exactly* how I
like to think when it comes to applying nomenclature to biodiversity.

Many thanks for your feedback!

Aloha,
Rich

=======================================================
Richard L. Pyle, PhD
Ichthyology, Bishop Museum
1525 Bernice St., Honolulu, HI 96817
Ph: (808)848-4115, Fax: (808)847-8252
email: deepreef at bishopmuseum.org
http://www.bishopmuseum.org/bishop/HBS/pylerichard.html