Farewell to Species - reticulation

[Hubert Turner]

At 08:11:27 -050015-02-2000, Thomas DiBenedetto <TDibenedetto at DCCMC.ORG> wrote:
>Could you give me an example of an internal branch that bears a
>species name? I am sorry, but Archaeopteryx lithographica doesnt cut
>it, because it is not an internal branch, at least not in any
>rigorous analysis that I have seen.  One might speculate that it was
>a direct ancestor of all other birds, but there is no evidence
>whatsoever to back up that hypothesis. [...] It has been pointed out
>many times that we simply do not have the empirical tools by which
>to support a hypothesis of direct ancestry.
Agreed, but then we don't always have the tools either to negate a
hypothesis of direct ancestry. If a particular branch in the network
is characterised by a number of apomorphies that make it part of a
particular clade, but has no autapomorphies, we can't say for sure
that it is *not* the ancestor of that clade. And the reason that
phylogenetic analyses (I assume those are the rigorous analyses
you're talking about) never show A. lithographica as the direct
ancestor of Aves is of course that phylogenetic analyses are not
intended to reconstruct ancestor-descendant relationships amongst the
units in the investigation, only sister-group relationships.
At 07:15 -0500 15-02-2000, Thomas DiBenedetto wrote:
>it is beyond my comprehension why anyone would advocate for a non-phylogenetic
>classification to be the basis of our naming system.
Phylogeny is important in naming, but not so important that only
monophyletic taxa should be recognised. Yes, it is desirable to have
each higher-level taxon descending from a single ancestor (which
should be included), but I don't see how creating paraphyletic taxa
(e.g. the genus Archaeopteryx, consisting of all the descendants of a
common ancestor, except the descendants of A. lithographica) can lead
to erroneous ideas about evolution, as long as one only assumes that
higher-level taxa have common ancestors. Does a not yet discovered
taxon lead to wrong ideas?
--

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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

FROM 18 JANUARY TILL MID-APRIL I WILL BE AT THE NEW YORK
BOTANICAL GARDEN AS VISITING SCHOLAR, DOING MOLECULAR
PHYLOGENETIC RESEARCH ON ANACARDIACEAE. MY REGULAR E-MAIL ADDRESS
WILL REMAIN FUNCTIONAL DURING THAT PERIOD.
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