Conceptual frames in taxonomy

Thomas Schlemmermeyer termites at USP.BR
Fri Sep 19 00:44:31 CDT 1997


Hi taxacomers, microbiologists especially,

=09Ivano wrote:
>I posted some messages to a couple
> of taxonomist which were discussing about cladistic, dendrograms etc.

As far as I know, cladistic approaches to bacterial systematics have been=
=20
made, primarily, by using ribosomal RNA sequences.
Such studies revealed unexpected high genetic diversity and only weakly=20
resolved phylogenies.

> Anyway, in microbiology systematics, is not so much relevant the geograph=
yc
> distribution as a tool for classification or identification of species, b=
ut
> a several of tests (biochemical, morphological, serological), and now
> nucleic acid and protein/enzymes analysis has been very much applied for
> this purpose.=20

In other organisms the geographic distribution is more the result=20
of identifying many specimen from many localities of the same species.
It is a result, not a tool!
Using geographic distribution as a tool for classification can be, as far=
=20
as I know, very dangerous.
Tools (Biochemical, morphological, genetical) can be quite similar in Pro-
and Eucaryota!

I guess that there is simply not enough knowledge about bacterial diversity
to make assumptions about species distributions.
I don't know if I'm right, but I think I already heard saying that bacteria
are the organisms with the highest ratio undescribed/described species.
And there isn't even a clear, well-defined species concept.

Maybe, such little organisms have amazing powers of dispersion?=20
Or are bacteria rather sedentary?
Surely this will depend on the taxon. (Does the species depend on a host,
is there a special life-stage for distribution, what environmetal extremes
can be supported.....? etc.)
Does anyone know more about this topic? Or is it unknown?

In comparing entomologists and bacteriologists I think that=20
bacteriologists work very habitat-orientated (bacteria from the gut,
bacteria from hot springs, bacteria in the industrial waste, bacteria
in the soil etc.), whereas entomologists work on whole geographical regions=
,
but usually only with a clearly delimited taxon.

Still not quite sure if this reflects historical facts, methodological
constraints or real properties of the organisms studied I send best wishes,

Thomas

 If I could help, I am open for=20
more discussion on this matter. >=20
> Best wishes,
>=20
> Ivano.
>=20
>=20
> >Dear readers,
> >
> >Surprisingly, after posting my last message, I received a feed-back by a
> >microbiologist, who is a member of the taxacom-list.
> >This leads me to post one more, even if not targeted, maybe, at least,
> >educated question:
> >
> >In Insect taxonomy, there is a broad conceptual frame based on Hennig's
> >phylogenetic systematics and vicariance biogeography.
> >Hennig developped his methods by dealing with bisexual, more or less
> >separated reproduction complexes of the insect order Diptera.
> >
> >Now my question: In what sense and up to which point, these methods make
> >sense in bacterial systematics as well?
> >
> >Especially:
> >In insects characters, usually, are said to be transferred vertically,=
=20
> >from ancestor to descendant.
> >Only in rare cases are discussed horizontal character transfers which th=
en
> >may show up in the cladistic analysis as homoplasy.
> >
> >What about the situation in bacterial systematics?
> >
> >Insect biogeography is supposed to be closely linked to geohistorical
> >events of separation of land masses etc.
> >Such approaches make sense in microbiology as well?
> >
> >Very interested in an intensiv discussion of the topic presented I send
> >my best wishes,
> >
> >                       Thomas

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Thomas Schlemmermeyer
Museu de Zoologia, Universidade de S=E3o Paulo
Caixa Postal 42694
CEP 04299-970
S=E3o Paulo, SP, Brasil

Resid=EAncia:
Thomas Schlemmermeyer
Caixa Postal 00276
CEP 14001-970
Ribeir=E3o Preto, SP, Brasil

Fone, Fax: 016 6371999
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