Dear Rodrigo,
Four species is too few to be able to tell with any confidence whether a
statistical model fitted with a star phylogeny or a hierarchical phylogeny
better fits your data. However, you can certainly analyze your data with both
conventional and phylogenetic methods (e.g., independent contrasts,
simulations). If the main result is similar with both approaches, then you
have your answer. If not, then ...
With that small a sample size, I would not bother with approaches that
transform the branch lengths. Here are two papers that present simulations
related to sample size:
Blomberg, S. P., Garland, Jr., T. and Ives, A. R. (2003). Testing for
phylogenetic signal in comparative data: behavioral traits are more labile.
Evolution 57, 717–745.
Freckleton, R. P., Harvey, P. H. and Pagel, M. (2002). Phylogenetic analysis
and comparative data: a test and review of evidence. The American Naturalist
160, 712–726.
Cheers,
Ted
Theodore Garland, Jr., Professor
Department of Biology
University of California, Riverside
Riverside, CA 92521
Office Phone: (951) 827-3524
Facsimile: (951) 827-4286 (not confidential)
Email: tgarl...@ucr.edu
http://www.biology.ucr.edu/people/faculty/Garland.html
http://scholar.google.com/citations?hl=en=iSSbrhwJ
Director, UCR Institute for the Development of Educational Applications
Editor in Chief, Physiological and Biochemical Zoology
Fail Lab: Episode One
http://testtube.com/faillab/zoochosis-episode-one-evolution
http://www.youtube.com/watch?v=c0msBWyTzU0
From: R-sig-phylo [r-sig-phylo-boun...@r-project.org] on behalf of Rodrigo
Gavira [rodgav...@gmail.com]
Sent: Sunday, July 10, 2016 12:38 PM
To: r-sig-phylo@r-project.org
Subject: [R-sig-phylo] data anlysis
Dear guys,
my name is Rodrigo, I am a PhD student from São Paulo State University,
Brazil. I am finishing my thesis but have some doubts about how to analyze
my data, so I decided contact you.
Here I am working on comparative physiology of ectothermic
vertebrates. In summary,
I work with 4 pitvipers species (*Bothrops* and *Crotalus* genus) in which
I measured: Metabolism, water loss by evaporation, and thermal preference
and tolerance. Now I would like to compare these results among species.
However, as I said, I have only four species to compare. From what I
understand when looking at mailing linst archives, this number of taxa are
not enough to test the effects of phylogeny on my results, and I must use
conventional analyzes. Is that right? If so, please, could you send me some
papers dealing with this?
Many thanks, guys. Cheers,
--
MSc. Rodrigo Samuel Bueno Gavira
Biologist - PhD student in Zoology
Universidade Estadual Paulista - UNESP
Department of Zoology
Rio Claro - SP - BRAZIL
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