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From: David Wright <dwright at u.washington.edu>

>OK, back to the branch on the tree of life. It is real, and
>exists whether we recognize it or not (that is, the historical
>pattern of descent is real). But the categorical names we apply to
>the branches -- "class," "order," "family," "genus," and yes, even
>"species" are not real: which branch gets which label is arbitrary. It
>is true that the species can be labeled more objectively, but there is
>more than one objective set of criteria on which to base this labeling,
>and deciding among them is arbitrary. It is possible to recognize the
>branches on the tree -- "clades" -- without assigning them to one of the
>ranked categories (family, genus, species, etc.).

I think the real problem is that the branches are not so real. Where
the branches are obvious, we haven't had problems of lumping and
grouping and changing of classifications.

As humans, we like to name things and we like discrete namable things.
Continua give us fits. Why are there seven colors in the rainbow
(ROYGBIV) when all the colors are present?

We tend to name the extremities. Sometimes, after scientific inquiry,
these are determined to be only morphs (i.e. dark morph and light
morph). Sometimes these are determined to be subspecies/races.
Sometimes these are species within a genus. Sometimes, what appears at
first to be a single population turns out to be two which are not even
related, but which have converged in morphology; look-alike
butterflies come to mind. Sometimes there is a continuum which
confounds our desire to pigeonhole.

My wife was studying a flower in the mallow family a few years back.
The plants in S. California could be crossed with plants from as far
north as southern Oregon. The plants from N. California could be
crossed with plants anywhere in California or Oregon. The Oregon
plants could be crossed with those in Washington. But plants from
Washington would not cross with California plants. This cline existed
all the way from California to Alaska. What do you name in such a
circumstance? How many species are there? Is this one branch or many?
If you look at the plants from S. California, Washington, and Alaska,
you'd definitely be tempted to name them different things, for they
look and grow very differently.

The same thing exists in birds. Hermit Warblers and Townsend's
Warblers have a geographic area in which there is a cline; from S to N,
the birds change from looking like Hermits to looking like Townsends in
a progressive manner. It doesn't help to have names for the end
points first, and to argue later about whether they comprise two
species or two subspecies, because the birds in the middle don't have a
fixed name. Are they AxB or are they all C? We are having the same
problem*10 with Gulls.

So I think it's safe to say that there will always be lumping a
splitting, regardless of how we choose to name what we see.
Publication of the current standard allows scientific communication
without confusion. As for what we count, claiming 500 species can be a
measure of achievement in a relative way. However, in absolute terms
it is artificial and unsatisfactory. Why not count males vs. females,
basic vs. alternate plumage, light morph vs. dark morph, race A vs. race B?

Wouldn't you feel just a bit of dissatisfaction with your 437th
species: Pavo cristatus, which you count because you saw a Peahen. But
you never saw a Peacock?

== Michael Hobbs
== Redmond WA
== mikeho at microsoft.com