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I think I agree with Chris that this thread does seem to be wearing
thin. Guess we will just have to agree to disagree for now. It ultimately
boils down to different views of speciation and how arbitrary one believes
it is to delimit species in time (or even space). Cladists claim to be less
arbitrary, but I just see new forms of arbitrariness replacing the old ones,
and that the pendulum has swung too far in the other direction. I guess we
won't know for sure any time soon. And Ghiselin's 1997 book is quite good,
although I suspect that what I got from it differs in many respects from
what Chris got from it.
But I disagree on one point Chris made in the last post. Even the
peer-reviewed literature of the last 20 years has plenty of admittedly
paraphyletic new taxa being named (although maybe not among vertebrates
where more cladistic editors and reviewers can nip them in the bud).
Probably one of the most brilliant and prolific proposers of new taxa
at higher levels is Thomas Cavalier-Smith, who presented his revised
six-kingdom system of life in 1998 (in Biol. Rev.). Just like me,
classifying all organisms has also made it obvious to him that paraphyletic
groups are inevitable, particularly at higher taxonomic levels.
He freely admits that his new Subkingdom Eomycota is paraphyletic, and
that a number of his other newly proposed taxa are "probably"
paraphyletic----not to mention many others he proposed in earlier papers and
paraphyletic taxa of other authors he recognizes.
His taxa are well-diagnosed, and certainly not proposed out of
ignorance, like some of the paraphyletic groups from the "old days". He
only divided Vertebrata down to Infraphyla (Agnatha and Gnathostomata), but
there is little doubt that he would recognize an Aves separate from a
paraphyletic Reptilia. But without Kinman markers, his classifications are
less cladist-friendly, and sometimes a little too old-fashioned as well
(e.g., I think he needs to get rid of Subkingdom Radiata).
What is important is that he recognizes it when he is creating
paraphyletic taxa, such as his admittedly paraphyletic Lophozoa, while the
molecular biologists are claiming that the even more inclusive
Lophotrochozoa is holophyletic. Other cladistic authors have no doubt named
paraphyletic taxa at lower taxonomic levels in the past 20 years
(particularly in botany). And of course, there are other purported
holophyletic taxa proposed by cladists that are probably really paraphyletic
(and they are more problematic when they go unrecognized). So it goes.
Finally, I think the demise of the Linnean System has been greatly
overstated. Purely cladistic classifications are so asymmetic (not having
the balance and stability that occasional paraphyletic groups can offer)
that they have put an enormous strain on the Linnean System. My philosophy
is to back off from some of that asymmetry (which can be destabilizing) and
modify the system to make it more cladist-friendly. I truly believe that
Chris and others underestimate the problems cladistics will encounter in the
future. But there again, only time will tell.
Looks like I am going to only post once today (and the crowd breaks out
in applause and cheers). Yeah, I know I can get worked up and ranty
sometimes, and then I settled back down for quite a while having gotten it
out of my system.
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