Re: The PhyloCode will not address the naming of species (Was The Papers That Ate Cincinnati)

["T. Michael Keesey" <keesey@gmail.com>]

On 5/8/07, Anthony Docimo <keenir@hotmail.com> wrote:
> how many times has that sort of thing been done with dinosaurs and other
> fossils?
>
> lots of times, I'm sure.

Dinosauria has been everything from a suborder (original designation)
to a class. But why would the mere fact that his sort of thing goes on
a lot excuse it? How many pages have been wasted arguing over whether
a given taxon should be a given rank, when ranks are biologically
meaningless? Why should we dither over them when we could be
discussing actual biological entities?

> by that logic, redwoods and poison ivy  are nothing more than part of a
> clade within the bacteria kingdom.

(Again, no ranks--get rid of that "kingdom".)

Bacteria (in the loose sense, meaning "prokaryote") are paraphyletic
with respect to eukaryotes, seeing as they are based on the lack of a
derived character (all terrestrial life forms without cellular
nuclei). In that sense you could say that eukaryotes are a type of
bacteria, but it's not really useful to convert "bacteria" to a clade
when that clade is just "Life" (or "Biota").

Redwoods and poison ivy, like all extant organisms, are part of many
clades, Some they share in common, like the clade of Life,
_Eukaryota_, _Plastida_, _Viridiplantae_, _Embryophyta_,
_Tracheophyta_, and _Spermatophyta_. Some include redwoods but not
poison ivy, such as _Coniferae_ and _Cupressaceae_. Others include
poison ivy, but not redwoods, such as _Angiospermae_, _Rosidae_,
_Sapindales_, and _Anarcadiaceae_.

> "Plants" are an illusion.

Well, the term is a loose one, but not illusory. It could be said to
correspond to either _Plastida_ or _Viridiplantae_. It might also be
possible to rigorously define _Plantae_ (but I'm not familiar enough
with nomenclature in that part of the Tree of Life to know how
feasible that is).

> (after all, there's no clear-cut edge to the Plant Kingdom, with with the
> protists that have plant features...and protists are an offshoot of
> bacteria, therefore...)

But there are clear-cut edges that can be recognized. For example,
_Plastida_ could be defined as the first ancestor of [insert extant
plant species here] to possess plastids ancestral to those in [that
same extant place species], and all descendants thereof. Or, depending
on which convention wins out (the PhyloCode is still in development,
after all), that definition could be used for _Apo-Plastida_, with
_Plastida_ being the largest crown group inside _Apo-Plastida_ (i.e.,
the last common ancestor of all extant organisms to possess plastids
homologous with those of [insert extant plant species here], and all
descendants of that ancestor).

> I see a very slippery slope.

Evolution is almost nothing *but* slippery slopes. But there are firm
groupings we can attach names to. Identify an ancestor using any one
of several methods (direct identification, node-based definition,
branch-based definition, apomorphy-based definition, etc.), add all
descendants of that ancestor, and, hey presto, you've got a natural,
rigorously-defined clade.
--
Mike Keesey