Yes, this would be circular. For instance, consider the situation in
which the data have no signal and thus the best branch-length
transformation (perhaps) would shorten all internal edges to 0, and
lengthen all terminal edges to a constant. K is guaranteed to be 1.0
(regardless of the data) on this tree (and any star tree).
I hope this is helpful. Sorry for the slow reply.
All the best, Liam
--
Liam J. Revell
University of Massachusetts Boston
web: http://faculty.umb.edu/liam.revell/
email: liam.rev...@umb.edu
blog: http://phytools.blogspot.com
On 8/12/2011 1:35 AM, Manabu Sakamoto wrote:
Hi everyone,
When performing Blomberg et al.'s test for phylogenetic signals, do the data
and/or branch lengths have to conform to the assumptions of Brownian motion as
discussed in Garland et al. (1992) and elsewhere, i.e. do contrasts have to be
adequately standardised? Or can data and branch lengths be the original
untransformed values?
I have the vague sense that it would be circular to make sure the data/branch
lengths conform to BM and then test for deviations from BM by computing K. Or
am I wrong to think this way?
many thanks,
Manabu
Manabu Sakamoto, PhD
Postdoctoral Research Associate
School of Earth Sciences
University of Bristol
Bristol, UK, BS8 1RJ
Tel: +44 (0) 117 954 5421
Fax: +44 (0)117 925 3385
Email: m.sakam...@bristol.ac.uk
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