pbs Digest, Vol 17, Issue 29

ConroeJoe@aol.com ConroeJoe@aol.com
Sun, 20 Jun 2004 13:54:24 PDT
In a message dated 6/20/2004 2:38:57 PM Central Daylight Time, 
pbs-request@lists.ibiblio.org writes:

> The preliminary data that we have based on ITS sequences show two 
> migrations
> out of Mexico... Interestingly, H. glauca (one of my
> favorite Mexican species) is sister to the other two Mexican clades.


Nice work I'm sure, I've read some of your manuscripts and they are well 
done, and -well-thought-out.

I've got to ask how you know that only tree branching occurred (clades), 
rather than reticulate branching (fusions) as well.  The clades-only approach is 
inconsistent with the evolution of some plant species and I've been trying to 
understand how this issue is finessed or directly addressed, as opposed to 
sidestepped.   So far I think I've mostly confused myself.  

When I've looked at single genes, it is easy enough to see proper clades.  
Recombination doesn't clutter the picture too much within a cistron.  But whole 
genomes present another picture altogether.  Hybridization events have 
produced some genomes that are fusions of clades and not bifurcations.  

Perhaps reticulation (where it occurs) only limits precision, while still 
allowing easy identification of major migrations?  

Conroe Joe


Reconstructing Reticulate Evolution in Species

Journey Into the World of Cladistics (if you dare)

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