> Mortberg wrote:
> > I think that sequence information should only be used if nothing else
> > works. If you can't identify any reliable morphological traits try
> > sequencing a couple of genes with broad outgroups. What to sequence is
> > hard to decide. Go for something linked to morphology or metabolism.
Now, I work on molecular phylogeny of viruses. I have published on
the mol phyl of Potyviridae, Geminiviridae, and have even dabbled my
toes in the murky and contested waters of papillomavirus phylogeny.
And you can't use morphology because all the viuses in a given family
look identical t one another. You can't use physiology because the
effects in the hosts of any one virus family are pretty much the
same. So, we used sequence - and have helped push the probable
evolutionary history back several hundred million years. This is
significant, given the complete absence of fossil viruses (outside of
endogenous retroviruses).
The above view expressed by friend Mortberg is terribly
plant/animal-centred in that it assumes there IS a usable morphology.
And most bacteria and all viruses will give the lie to that, at the
familial level of taxonomy at least.
> Miriam Richards wrote:
> Just for the record, I am one of "those molecular people" who uses both
> parsimony and outgroup analysis whenever possible, having been trained by
> a tough morphological systematist who also uses molecular data. But not
> being a religious person, I have occasionally also been known to do
> neighbour-joining and maximum likelihood analyses.
So true...I have written here before about using PAUP until the data
sets get too large, then using a neighbour-joining distance
method...heresy to the purists, but hey, what we've checked out is
consistent - and it works for us.
______________________________________________________
| Ed Rybicki, PhD | ed at molbiol.uct.ac.za |
| Dept Microbiology | University of Cape Town |
| Private Bag, Rondebosch | 7700, South Africa |
| fax: x27-21-650 4023 | phone: x27-21-650-3265 |
------WWW URL: http://www.uct.ac.za/microbiology------
"And then one day you find, ten years have got behind you"
