Cladistics and "Eclecticism"

[Robin Leech]

Why cannot a lineage evolve with no side or splinter groups?  Why cannot
a species change morphologically/physiologically during time and during that
time
be all alone?  Why cannot there be montotomous events?  Why does there
ALWAYS have to be a sister group or sister groups?

I can envision a wide-spread species, morphologically very similar
throughout
its range, becoming extinct in all but one small area, and in due course of
geological time, the survivors change morphologically (your reasons -
habitat,
genetic drift, mutation - I will not argue the "why" here) and
physiologically.

Somewhere, surely, there must be a real lineage - as the word indicates - a
line!

I agree with Thomas Lammers - the assumptions have built a castle in the
sky, and some now continue to support the castle because some say it is
there, some others report that they have seen it, etc., when in fact it may
be
no more than a dense cloud with a form that some see as a castle.

Robin Leech

----- Original Message -----
From: "Thomas DiBenedetto" <tdib at OCEANCONSERVANCY.ORG>
To: <TAXACOM at USOBI.ORG>
Sent: Monday, February 04, 2002 10:31 AM
Subject: Re: Cladistics and "Eclecticism"


> -----Original Message-----
> From: Thomas Lammers
> My problem is that I do not believe the assumptions and
> methodologies of cladistics (all speciation is dichotomous, ancestral taxa
> go extinct at the point of bifurcation, etc.) allow us to ecover
> "recognized lineage groups".
> *****************
> I have never in my life encountered a cladist who denied the possibility
of
> polytomous speciation. Please be assured that, at the very least, most, if
> not all, cladists do not make such an assumption, and such an assumption
is
> not a necessary assumption of cladistics.
> As to your second claim, I cannot see how you can aasert that this is a
> necessary assumption of cladistics either. I have posted many times, in
> great detail on my cladistic understanding of this issue. I wonder why you
> seem not to take those points into account. To briefly summarize:
Ancestral
> taxa do not go extinct unless they go extinct; i.e. unless all the
organisms
> die. Ancestral taxa become higher taxa when some of their descendants
become
> historically isolated from others of their descendants, i.e when the
lineage
> bifurcates. The only thing that comes to an end at the point of
bifurcation,
> is the simple fact that the ancestral taxon was a terminal branch in the
> lineage system, and thus ranked as a species. After bifurcation, it's
status
> as a species-level taxon is finished. It's life as higher level taxon is
> just beginning. How can this be considered "extinction"?
>
> Maybe, when you get right down to it, you don't have any real problems
with
> claditics - :)
>
> Tom DiBenedetto
>