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Re: The Papers That Ate Cincinnati



On 5/6/07, Anthony Docimo <keenir@hotmail.com> wrote:

Ahh, okay; so PhyloCode says which species are in groups together.

No, the PhyloCode says nothing about the relationships of species. That's the work of science, not of nomenclature.

The PhyloCode dictates which clade (if any) to attach a clade name to
*under a given phylogenetic hypothesis*. For example, _Dinosauria_
could be defined as the last common ancestor of _Megalosaurus
bucklandii_, _Hylaeosaurus armatus_, and _Iguanodon bernissartensis_,
and all descendants of that ancestor. What belongs in _Dinosauria_,
then, depends on the hypothesis. For example under this topology, it
would not include _Silesaurus_:

(Silesaurus, (Megalosaurus, (Hylaeosaurus, Iguanodon)))

But under this topology, it would include _Silesaurus_:

(Megalosaurus, (Silesaurus, (Hylaeosaurus, Iguanodon)))

The PhyloCode's job is not to tell us the phylogenetic position of
_Silesaurus_. It's to tell us whether _Silesaurus_ is a dinosaur
*given a certain phylogenetic position*. (And, in the case of
apomorphy-based definitions, other data may be needed as well.)

 I can
grasp that.....its like the clade diagrams  of a long diagonal / line from
an ancestor to a modern species (ie mammal-like reptile to a cow), with
other \ lines shooting off at intervals marked with such things as
"development of live birth" just after the line leading to a platypus &
"development of a placenta" just after the line to a kangaroo, etc.

Cladograms, yes. Those labels signify apomorphies, and, by extension, apomorphy-based clades. But the PhyloCode itself isn't about producing cladograms--it's more about where to place the names given a certain cladogram.

(Incidentally, "mammal-like reptiles" are often not considered
reptiles any more. A better, more succinct term would be
"stem-mammals".)

  Now that I see how PhyloCode works for the big groups, how does it work
for the little ones?  Returning to hoatzins, how does it distinguish
between, say, _Opisthocomus hoazin_ and _Opisthomus paradoxus_?

(yes, I made up the second one, just to simplify things)

The first version of the PhyloCode is actually not going to cover species. Those will continue to fall under the domain of the current codes (ICZN, etc.).

--
Mike Keesey