Farewell to Species - reticulation

[Curtis Clark]

At 06:13 PM 00.02.13 -0500, Thomas DiBenedetto wrote:
>When a taxon, ranked as a species (because it is
>terminal) diverges, then it is not equal to the internal branch, it is
>equal
>to, as always, the original ancestor and all of its descendants. It has
>evolved into a higher ranking taxon.

So you are saying that the species rank is defined as being terminal: not a
problem, I see your point, everything you say makes sense in that light.
But the term species has another meaning (several, actually, if we get into
BSC and such, but I'll focus on the one I like): the smallest group within
which relationships are tokogenetic, but relationships with other species
are phylogenetic. By this definition (or even by BSC), that first mammal
was probably a species. It doesn't matter one whit how we rank it now, but
when ancestral species are "still around" (in the tokogenetic continuity
sense), it muddies the waters for them to become higher taxa when many of
us are still (productively) using other species concepts.

Ironically, all this is an additional argument for rankless classification,
since we could have our species and diverge them, too.
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