These descriptive statistics (e.g., K of Blomberg et al. 2003) and related tests do not require normality of the data under analysis. However, your results may be highly dependent on the type of transform you use (or do not use), so all results must be considered in the context of that transform. In general, I'd be inclined to apply some sort of "sensible" transform, such as log, if I were working with a large number of species that varied widely, such as body masses of mice to elephants. Check the Blomberg et al. (2003) paper for a bit more discussion about this, and to see what they did for the various traits studied.
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&user=iSSbrhwAAAAJ 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 Ting-Wen Timothy Chen [tch...@gwdg.de] Sent: Wednesday, April 13, 2016 11:02 AM To: r-sig-phylo@r-project.org Subject: [R-sig-phylo] Normal distribution in trait values before testing for phylogenetic signals? Hi all, I'm working on the phylogenetic signal tests for continuous traits using K statistics and Pagel's lambda implemented in phytools. I'd like to know whether normal distribution of the trait values must be tested before phylogenetic signals are tested, and if the trait data are not normal distributing, do I have to transform the data? I have looked for this issue in my paper collections as well as on the internet, but still have no idea. It would be very nice if someone can give me some advice, or any paper/reference/website would also be very helpful. Thanks a lot! Best, Ting-Wen -- Ting-Wen Chen J.F. Blumenbach Institute of Zoology and Anthropology Georg August University Goettingen Berliner Str. 28 D-37073 Goettingen, Germany Tel: +49-55139-10943 _______________________________________________ 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/ _______________________________________________ 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/
