Testing for phylogenetic signal in comparative data: Behavioral traits are more labile

Blomberg, Simon P., Garland, Theodore Jr and Ives, Anthony R. (2003) Testing for phylogenetic signal in comparative data: Behavioral traits are more labile. Evolution, 57 4: 717-745. doi:10.1554/0014-3820(2003)057[0717:TFPSIC]2.0.CO;2

Author Blomberg, Simon P.
Garland, Theodore Jr
Ives, Anthony R.
Title Testing for phylogenetic signal in comparative data: Behavioral traits are more labile
Journal name Evolution   Check publisher's open access policy
ISSN 0014-3820
Publication date 2003-04-01
Sub-type Critical review of research, literature review, critical commentary
DOI 10.1554/0014-3820(2003)057[0717:TFPSIC]2.0.CO;2
Volume 57
Issue 4
Start page 717
End page 745
Total pages 29
Place of publication Lancaster, PA.
Publisher Society for the Study of Evolution
Language eng
Abstract The primary rationale for the use of phylogenetically based statistical methods is that phylogenetic signal, the tendency for related species to resemble each other, is ubiquitous. Whether this assertion is true for a given trait in a given lineage is an empirical question, but general tools for detecting and quantifying phylogenetic signal are inadequately developed. We present new methods for continuous-valued characters that can be implemented with either phylogenetically independent contrasts or generalized least-squares models. First, a simple randomization procedure allows one to test the null hypothesis of no pattern of similarity among relatives. The test demonstrates correct Type I error rate at a nominal alpha = 0.05 and good power (0.8) for simulated datasets with 20 or more species. Second, we derive a descriptive statistic, K, which allows valid comparisons of the amount of phylogenetic signal across traits and trees. Third, we provide two biologically motivated branch-length transformations, one based on the Ornstein-Uhlenbeck (OU) model of stabilizing selection, the other based on a new model in which character evolution can accelerate or decelerate (ACDC) in rate (e.g., as may occur during or after an adaptive radiation). Maximum likelihood estimation of the OU (d) and ACDC (g) parameters can serve as tests for phylogenetic signal because an estimate of d or g near zero implies that a phylogeny with little hierarchical structure (a star) offers a good fit to the data. Transformations that improve the fit of a tree to comparative data will increase power to detect phylogenetic signal and may also be preferable for further comparative analyses, such as of correlated character evolution. Application of the methods to data from the literature revealed that, for trees with 20 or more species, 92% of traits exhibited significant phylogenetic signal (randomization test), including behavioral and ecological ones that are thought to be relatively evolutionarily malleable (e.g., highly adaptive) and/or subject to relatively strong environmental (nongenetic) effects or high levels of measurement error. Irrespective of sample size, most traits (but not body size, on average) showed less signal than expected given the topology, branch lengths, and a Brownian motion model of evolution (i.e., K was less than one), which may be attributed to adaptation and/or measurement error in the broad sense (including errors in estimates of phenotypes, branch lengths, and topology). Analysis of variance of log K for all 121 traits (from 35 trees) indicated that behavioral traits exhibit lower signal than body size, morphological, life-history, or physiological traits. In addition, physiological traits (corrected for body size) showed less signal than did body size itself. For trees with 20 or more species, the estimated OU (25% of traits) and/or ACDC (40%) transformation parameter differed significantly from both zero and unity, indicating that a hierarchical tree with less (or occasionally more) structure than the original better fit the data and so could be preferred for comparative analyses.
Keyword Ecology
Evolutionary Biology
Genetics & Heredity
body size
branch lengths
comparative method
Computer-simulation Test
Sexual Size Dimorphism
Life-history Traits
Independent Contrasts
Correlated Evolution
Anolis Lizards
Phrynosomatid Lizards
Continuous Characters
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown
Additional Notes This document is a journal review.

Document type: Journal Article
Sub-type: Critical review of research, literature review, critical commentary
Collections: Excellence in Research Australia (ERA) - Collection
School of Biological Sciences Publications
Ecology Centre Publications
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Created: Thu, 20 Sep 2007, 02:40:19 EST