Farewell to Species - reticulation

Stuart Fullerton stuartf at PEGASUS.CC.UCF.EDU
Tue Feb 15 07:06:11 CST 2000

gentlemen - and i stress the gentle. could you continue this on a private
line. i am getting a tad tired of pushing the deleat button and may get
rps from it.

thanks and cheers!  it has been fun.  rof

On Tue, 15 Feb 2000, Hubert Turner wrote:

>  ; margin-bottom: 0 }  -->n
> No. You just dont seem to get it.
>  YOU just dont seem to get it!!! All I want is to be able to refer to a
> particular internal branch by a particular name. And that name is sometimes
> already available, namely a species name. That at a certain point
> Archaeopteryx lithographica branched onto several descendant species and at
> that very moment stopped existing doesn't matter. The specimen that was
> covered with limestone in the deposits near what was later to become the
> city of Solnhofen was part of a lineage characterised by a number of
> synapomorphies, but the animal did not yet display further apomorphies that
> were to develop only later in the lineage (e.g. webbed feet, such as
> present-day ducks have). What is the objection against referring to that
> particular branch (starting at a split and ending at the very next split)
> by a name at species level? When that branch was terminal, it was referred
> to as a species, so why not continue to do so? Of course it is also part of
> a larger clade which also includes all of its descendants, but it is also
> part of a still larger clade that includes all vertebrates, which are part
> of an even larger clade that includes all metazoans, etc. etc. But the same
> goes for e.g. Parus major, or Homo sapiens, two terminal branches which you
> don't seem to mind naming as species. But just because we do not know if
> Parus major is split into different entities (Parus aus and Parus bus) does
> not mean that it will never do so. In fact, it may already have split up,
> only we haven't recognised it (yet).
> It is probably the most basic
> point of phylogenetic systematics, that taxa are meant to refer to real
>  monophyletic groups. 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.
>  ----------------------
>  Yes, it has evolved into a higher taxon, consisting of the ancestor
> (branch 3) and its descendants (branches 1 and 2). But the clade is not the
> same thing as the ancestor, at least not in terms of taxonomic rank. The
> clade is the same thing as the lineage that started with branch 3, I'll
> give you that. But I don't see how you can talk about the original ancestor
> as a separate unit, but do not want to be able to refer to it by any other
> name than the very vague 'original ancestor' (BTW, what is an unoriginal
> ancestor? ;-) ). My point is that the branch in the phylogeny that you
> identify as the ancestor should bear the taxonomic rank of species, and
> should be named accordingly. Following Hennig, as I pointed out before,
> any segment of a lineage between to branching points could be called a
> species, whether it terminates  in the present, or by extinction, or by
> further branching.
> By what logic or definition must it still be considered a species? What is
>  so problematical about using the past tense to describe something that no
>  longer exists? Species is a rank. As a rank, it has conventionally been
> applied to taxa deemed to be terminal.
>  But it has conventionally been applied to Archaeopteryx lithographica and
> other assemblages of individual specimens that might have been ancestors of
> later species, and as such were not deemed to be terminal.
>  When a taxon is terminal and
>  unbranched, it is ranked as a species. When it aint, it aint. When it is
>  branched it is a higher taxon. When it is internal, and defined in isolation
> from its descendants, it is an artificial, paraphyletic assemblage.
> -------------
>  tdib previously:
>  The taxon is the ancestor and all its descendants.
>  ---------------
>  HT:
>  As I said, rubbish!!! In traditional (i.e. nomenclatural) usage,
>  taxon is any grouping of species, from the least inclusive (1
>  species)  to the most (phyla). Don't try to redefine the meaning of
>  "taxon".
> -----------------
>  Its not me doing any redefining. The definition I presented has been
> standard for quite some time.
>   I feel you confuse the term 'taxon' with the term 'clade'. I see no
> reason not to give names (at the species level) to internal branches. I
> agree that it would not be desirable to formally name paraphyletic grades
> (such as reptiles, or something like 'Protomagnoliaceae'). But for genera
> the codes leave us no other choice (apart from just not naming ancestral
> taxa) than to erect paraphyletic genera.
>  Hubert Turner--
>  *******************************************************
>  Dr. Hubert Turner
>  EEW, Sect. Theoretical Biology & Phylogenetics
>  PO Box 9516, 2300 RA  Leiden, The Netherlands
>  Visiting address: Van der Klaauw Laboratory, Kaiserstraat 63, Leiden
>  Phone: +31-71-5274904    Fax: +31-71-5274900
>  E-mail: turner at rulsfb.leidenuniv.nl
>  WWW: http://wwwbio.leidenuniv.nl/~turner/index.html
>  *******************************************************

Stuart M Fullerton ROF, Research Associate in charge of Arthropod
Collections (UCFC), Dept. of Biology, University of Central Florida, PO
Box 162368, Orlando, Florida, 32816-2368, USA. stuartf at pegasus.cc.ucf.edu
(407) 823-6540 (no voice mail)

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