Rafael,
a phylogenetic paired t-test should do the job. Please check this
reference:
Lindenfors P, Revell LJ, and Nunn CL. Sexual dimorphism in primate
aerobic capacity: a
phylogenetic test. J Evolution Biol 23: 1183-1194, 2010.
Liam, any comments on this?
Enrico
Rafael Maia escribió:
Hello everyone,
first of all, I would like to apologize if this question is too basic. I've
been trying to study comparative methods and their implementation in R for
several months now, but haven't taken any formal courses on it, so maybe I'm
missing something extremely obvious. I also apologize since this isn't
necessarily R-related, but this seemed like a good forum to ask...
My question relates to the evolution of ornamental colors. Specifically, I am interested
in comparing ornamental and non-ornamental colors in birds over a range of species, in
order to test if ornamental colors (trait A) are "showier" than non-ornamental
ones (trait B). Both traits are measured in the same scale, and are in the same unit.
>From what I understand of independent contrasts, the independence of data points is achieved by obtaining phylogenetically independent values of the change of these traits in a node. This makes a lot of sense to me if you are asking a question of if these traits are evolving in a correlated fashion, so that you'd expect a change in one of them to be accompanied by a change in the other.
However, this is not necessarily what I am interested in. I would actually like
to know if the changes in these traits occur in a manner in which, even if they
are changing independently, trait A is *always larger* than trait B. So, for
example, trait A might remain very similar between two species (i.e. low
contrast), whereas trait B changes a lot (high contrast), but trait B is still
lower than trait A in both species. Thus, a correlation of contrasts does not
seem to tackle my issue. In a similar manner, comparing contrasts of both
traits under a t-test does not seem to do the trick either, since contrasts
will reflect the variation in the variables over the phylogeny, and as I said,
this does not seem to be a question of how the variations in the variables are
associated...
after banging my head against the wall for weeks with this issue, I'm not even sure if
this question should actually be asked in a phylogenetic context - would simply comparing
the ratio of trait A x trait B across these species suffice? It doesn't seem so, since
common descent is expected to play a role in their evolution. However, I am not sure
anymore what is the "right question" to address my hypothesis anymore...
Any thoughts would be deeply appreciated.
Many thanks in advance!
Abraços,
Rafael Maia
---
webpage: http://gozips.uakron.edu/~rm72
"A little learning is a dangerous thing; drink deep, or taste not the Pierian
spring." (A. Pope)
Graduate Student - Integrated Bioscience
University of Akron
http://gozips.uakron.edu/~shawkey/
_______________________________________________
R-sig-phylo mailing list
R-sig-phylo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-phylo
--
*******************************************************************
Enrico L. Rezende
Departament de Genètica i de Microbiologia
Facultat de Biociències, Edifici Cn
Universitat Autònoma de Barcelona
08193 Bellaterra (Barcelona)
SPAIN
Telephone: +34 93 581 4705
Fax: +34 93 581 2387
E-mail: enrico.reze...@uab.cat
_______________________________________________
R-sig-phylo mailing list
R-sig-phylo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-phylo
