NANFA-- species concepts (long)

Dave Neely (
Mon, 24 Jan 2000 21:17:02 CST

Bruce, Ray, Jan, and other interested folk...

Jan's assertion that we should maintain subspecies is well taken, but seems
somewhat problematic; if our assessments of species identity are purely
arbitrary (Mayr's "species are what a competent taxonomist says they are"),
then there is no way to delineate what's a subspecies, what's an ESU (Waples
definition), what's a phylogroup (Avise's definition), or any of the other
convoluted attempts to describe population variation. Scientists fight with
each other because they can't see the appropriate characters, that one feels
is important enough to recognize something as a "species." This is a 5th
grade playground mentality that resulted in a TON of diversity in North
America to go unrecognized, because somebody at Tulane or the UMMZ didn't
THINK some population was different enough to be recognized. That's bad
science, any way you look at it.

Yeah, there's a lot of subspecies names still floating around. That doesn't
necessarily mean these things are getting the protection that they need.
Subspecies names give no additional information about phylogeny... because
most of them were recognized back when one just sat down and eyeballed a
bunch of fish and then made some regal proclamation in Copeia! (Ah, the Good
Old Days!)

>The truth of the matter is that there are various species concepts used and
>debated, depending on the organisms in question.

An optimal species concept should apply to all diversity on Earth. There's
only one (the ESC) that can do that. Yes, there's some 23 species concepts
out there (and NO I'm not going to go through all of them!). All except the
ESC fail to include some groups of organisms.

(As a parallel, Newtonian physics works fine when you are dealing with
things you see around you, but general relativity explains things across a
much broader scale. It's almost the same with the BSC and ESC...except for
that bit about allopatric species I mentioned earlier).

>The Evolutionary Species Concept that Dave describes was developed >largely
>out of the development of cladism as an organizing structure >(and
>philosophy, as the others) for systematics. Cladistics is based >on drawing
>cladograms, branching structures representing living >groups organized on
>the basis of shared, derived
>characteristics. The more in common by your measurements, the closer they
>are in sharing recent common ancestry.

It's not a "similarity" thing. It works by assuming that change in shared,
derived characters reflects the history of the group, and asserts that the
simplest explanation is the best-supported hypothesis!

>It can be criticized for assuming too much about speciation
>events in the past within its methodology, and doing it in a very
>rigid,ideological fashion. This leads to an inherent assumption of
>evolutionary tendencies and historical fates, which I have a problem >with.

We're not soothsayers. There's no implied anything about the future. The
question is whether populations represent discrete entities, that are
maintaining an independent lineage. Here's the fun part- you can use the BSC
(and many of the rest of those 23 species concepts)to get at this...

>Speciation and evolutionary events in general are not predictable >events;
>there is a large (but indeterminate) element of chance in >these processes.

Yes, that's ENTIRELY the point! That's why making inferences about phylogeny
from similarity or distance matrices (as is often done by population
geneticists) is bad. Changes in rates can give you faulty estimates of
phylogeny. Maximum parsimony methodologies are rate-independent.

>As a working organismal biologist I still use Ernst Mayr's Biological
>Species Concept as my starting point -- "Species are groups of
> >interbreeding natural populations that are reproductively isolated >from
>other such groups."

A friend of mine (who happens to be a psychology student) brought up the
hypothesis that Mayr's hangup with interbreeding comes from some deep-rooted
Teutonic obsession with sex (I'm half-German, half-Irish; I'm allowed to say
this ;). Considering a large proportion of life on Earth is asexual, I'd
have to agree that it seems rather eukaryotomorphic.

As for Chris' point about the loss of information from the trinomial:
There's actually several different species of <Siphateles> that are being
elevated out of "<bicolor>." They are not particularly closely related!
There's no way to tell that from any trinomial.

In short, the appearance of more information in a trinomial is illusory. As
for my own research on western mottled sculpins, it appears that populations
of mottled sculpin west of the Continental Divide might be more closely
related to things like <Cottus rhotheus> and <Cottus extensus> than they are
to "real" (Ohio River) <Cottus bairdi>. <Cottus "bairdi fumorum"> from the
Smokies may be more closely related to <Cottus carolinae> than it is to
other "<bairdi>."
Ray, this is why your beloved "Roloffia" was sunk. It's not about splitting
for splitting's sake- when done right, it provides a critical framework for
information retrieval.

Why is this important? Well, CFI is currently rearing <Erimystax insignis>
and <E. dissimilis> (sister species to the Federally Endangered <Erimystax
cahni>) to gain an idea of what techniques might work best in captive
propagation of <E. cahni>, a species that is too imperiled to risk
inappropriate techniques on. Comparative biology (using information about
phylogeny) provides a framework to better understand almost all aspects of
biology: evolutionary biology, physiology, ecology, behavior, etc.

My major professor (Rick Mayden) recently published a very comprehensive
treatment of species concepts and thier application- if anyone wants, I can
send a few copies out...

Sorry it took me so long to get back to your posts- I took the weekend off
and went kayaking, and got back to an overload of work. Blah.


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