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Re: Reduced Consensus (Was: Afrotheria revisited)



On 3/22/07, Michael Mortimer wrote:
Reweighting's an interesting thing that I've just begun
to experiment with.  Basically it makes characters which reverse or coverge
more than others worth less in the analysis.  Of course, you have to run the
analysis once to figure out what characters reverse or converge less, and
that makes me wary.  Also, does the fact a character coverges or reverses
make it less valuable?  And unless you include all relevent taxa (which
virtually no analysis does/can), you won't catch all the times a character
reverses or converges, so the value PAUP uses to determine its weight will
be off.


I've also been experimenting with reweighting because of Mickey mentioning it. An interesting example of its effects with Prieto-Marquez et al. (2006): Without reweighting- Strict consensus of 64 MPTs, TL-334 steps, CI- 0.61 |--I. bernissartensis |--I. atherfieldensis `--+--Probactrosaurus `--+--Ouranosaurus `--+--Protohadros `--+--Bactrosaurus |--Gilmoreosaurus `--+--Telmatosaurus |--Tanius `--+--Pararhabdodon `--+--Koutalisaurus |--Amurosaurus |--Hypacrosaurus stebingeri |--H. altispnius |--Edmontosaurus |--+--Olorotitan | `--Parasaurolophus |--+--Lambeosaurus | `--Corythosaurus `--+--+--Brachylophosaurus | `--Maiasaura `--+--Gryposaurus `--+--Prosaurolophus `--Saurolophus 50% majority rule |--I. bernissartensis |--I. atherfieldensis `--+--Probactrosaurus `--+--Ouranosaurus `--+--Protohadros `--+--Gilmoreosaurus `--+--Bactrosaurus `--+--Telmatosaurus |--Tanius `--+--Pararhabdodon `--+--+--H. altispinus | |--+--Parasaurolophus | | `--Olorotitan | `--+--Koutalisaurus | |--H. stebingeri | `--+--Amurosaurus | `--+--Lambeosaurus | `--Corythosaurus `--+--Edmontosaurus `--+--+--Brachylophosaurus | `--Maiasaura `--+--Gryposaurus `--+--Prosaurolophus `--Saurolophus

Now with reweighting-
Strict consensus of 3 MPTs, TL-165.8, CI-0.78
Bactrosaurus and Gilmoreosaurus are sister taxa, and Koutalisaurus
falls out as a basal hadrosaurine.

And for people who might be curious, a composite OTU scored with
codings from Pararhabdodon and Koutalisaurus (given Koutalisaurus was
originally material referred to Pararhabdodon, see Casanovas et al.,
1999), finds itself as a basal hadrosaurine in the unweighted run (24
MPTs, TL- 335), and outside of the Euhadrosauria in the weighted run
(1 MPT, TL-165.8), hmm

Nick Gardner