I agree with everything that Liam wrote -- right on. Another point is that if you are looking at morphometric traits, then most of them are probably highly positively correlated with body size. In that case, testing for phylogenetic signal in, say, wing length, is going to be largely redundant with testing for signal in body mass. Hence, for your traits other than body size, you may want to analyze size-corrected values, as described here:
Blomberg, S. P., T. Garland, Jr., and A. R. Ives. 2003. Testing for phylogenetic signal in comparative data: behavioral traits are more labile. Evolution 57:717–745. Cheers, Ted Theodore Garland, Jr., Distinguished Professor Department of Evolution, Ecology, and Organismal Biology (EEOB) 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&user=iSSbrhwAAAAJ Director, UCR Institute for the Development of <http://idea.ucr.edu/>Educational Applications <http://idea.ucr.edu/> Editor in Chief, *Physiological and Biochemical Zoology <http://www.press.uchicago.edu/ucp/journals/journal/pbz.html>* Fail Lab: Episode One *https://www.youtube.com/watch?v=c0msBWyTzU0 <https://www.youtube.com/watch?v=c0msBWyTzU0>* On Fri, Jul 13, 2018 at 12:29 PM, Liam J. Revell <liam.rev...@umb.edu> wrote: > Dear Alyson. > > There is no general rule about this; however, my suggestion would be to > use log-scaled values. This is because on a log-scale proportional changes > in the trait are equal, independent of the magnitude of the trait. That is, > a change of 1% in mass of whale is the same as a change in 1% in mass of a > mouse. If your analysis includes both mice and whales, then on the original > scale mice may appear to be changing very little in mass, while whales > change a great deal - even if (relative to their sizes) both groups are > changing just as much. On the other hand, if your analysis is of only > whales or only mice it will make relatively little difference whether you > use log-scaled data or the original values. > > I hope this is of some help. All the best, Liam > > Liam J. Revell, Associate Professor of Biology > University of Massachusetts Boston > web: http://faculty.umb.edu/liam.revell/ > > On 7/13/2018 2:07 PM, Alyson Brokaw wrote: > >> Hello Everyone, >> >> I am working with a comparative dataset using bat morphometrics. As part >> of >> my analysis, I want to estimate the phylogenetic signal of my variables. I >> understand how to do this using R. My question is more specifically about >> what kind of data I should be using when calculating the estimates. >> >> For the purposes of my other analyses (linear regressions), I have >> log-transformed my data to meet assumptions for normality. When estimating >> phylogenetic signal, should I use my non-transformed, raw variables or the >> transformed variables? I get slightly different outputs if I run both on >> the same measure. My intuition is that using the raw values is more >> interpretable, but figured I would ask some people with more experience. >> >> Thank you for your time. >> >> -Alyson >> ____________________________________________________________ >> >> Alyson Brokaw >> M.S. Candidate: Biology, Humboldt State University >> Cornell University '11, Ecology and Evolutionary Biology >> >> LinkedIn Profile <http://www.linkedin.com/pub/alyson-brokaw/3a/704/820> >> Follow my research journey here! <http://afbrokaw.wordpress.com/> >> >> [[alternative HTML version deleted]] >> >> _______________________________________________ >> R-sig-phylo mailing list - R-sig-phylo@r-project.org >> https://stat.ethz.ch/mailman/listinfo/r-sig-phylo >> Searchable archive at http://www.mail-archive.com/r- >> sig-ph...@r-project.org/ >> >> > _______________________________________________ > R-sig-phylo mailing list - R-sig-phylo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-phylo > Searchable archive at http://www.mail-archive.com/r- > sig-ph...@r-project.org/ > [[alternative HTML version deleted]] _______________________________________________ R-sig-phylo mailing list - R-sig-phylo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-phylo Searchable archive at http://www.mail-archive.com/r-sig-phylo@r-project.org/
