One origin? (viral evolution)

Sat Jul 21 11:59:16 CDT 2001

At 01:20 PM 7/20/01 -0500, Thomas Lammers wrote:
>At 09:54 AM 7/20/01 -0700, Curtis Clark wrote:
>>Snakes are tetrapods, even though they have no legs, because they are
>>members of the tetrapod clade, descended from the first tetrapods.
>>Likewise, eukaryotes are a clade, and eubacteria may be a clade (although
>>I know that Ken disagrees), but "prokaryotes" are a grade.
>>If a mammalian virus is a piece of mammalian DNA gone astray, it is a
>>eukaryote, and in fact it is a mammal. Viruses being what they are, they
>>have little trace of their ancestry, but I would venture that the
>>differences in gene regulation and genome structure between eubacteria and
>>eukaryotes might be reflected in viral genomes, and that we could thus
>>understand their relationships.
>>"Defining" prokaryotes and eukaryotes by their nuclei is essentialist.
>>Let's instead ask what we can infer about lineage groups.
>All well and good.  But I think that cladistic phylogeny carries with it an
>unstated assumption that the evolutionary events it reflects are the result
>of sexual reproduction of whole organisms, n'est ce pas?   I do
>not  believe the methodology functions well when we are dealing with bits
>of the organism that have taken on a life of their own.
>It seems to me that cladistic phylogeny is much more analogous to descent
>by asexual reproduction than by sexual reproduction.  I am certainly not
>fully up to speed in the field, but am unaware of any ways in which the
>cladistic model takes into account such events as hybridization,
>polyploidy, and parallel evolution and accordingly think the cladistic
>model is weakened in direct proportion to the extent to which this is so.
>Thomas G. Lammers, Ph.D.
>Assistant Professor and Curator of the Herbarium (OSH)
>Department of Biology and Microbiology
>University of Wisconsin Oshkosh
>Oshkosh, Wisconsin 54901-8640 USA
>e-mail:       lammers at
>phone:      920-424-1002
>fax:           920-424-1101
>Plant systematics; classification, nomenclature, evolution, and
>biogeography of the Campanulaceae s. lat.
>"Today's mighty oak is yesterday's nut that stood his ground."
>                                                 -- Anonymous

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