A robust new metric of phenotypic distance to estimate and compare multiple trait differences among populations

Rebecca J. Safran, Samuel M. Flaxman, Michael Kopp, Darren E. Irwin, Derek Briggs, Matthew R. Evans, W. Chris Funk, David A. Gray, Eileen A. Hebets, Nathalie Seddon, Elizabeth Scordato, Laurel B. Symes, Joseph A. Tobias, David P L Toews, J. Albert Uy

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Whereas a rich literature exists for estimating population genetic divergence, metrics of phenotypic trait divergence are lacking, particularly for comparing multiple traits among three or more populations. Here, we review and analyze via simulation Hedges' g, a widely used parametric estimate of effect size. Our analyses indicate that g is sensitive to a combination of unequal trait variances and unequal sample sizes among populations and to changes in the scale of measurement. We then go on to derive and explain a new, non-parametric distance measure, Δp, which is calculated based upon a joint cumulative distribution function (CDF) from all populations under study. More precisely, distances are measured in terms of the percentiles in this CDF at which each population's median lies. Δp combines many desirable features of other distance metrics into a single metric; namely, compared to other metrics, p is relatively insensitive to unequal variances and sample sizes among the populations sampled. Furthermore, a key feature of Δp-and our main motivation for developing it-is that it easily accommodates simultaneous comparisons of any number of traits across any number of populations. To exemplify its utility, we employ Δp to address a question related to the role of sexual selection in speciation: are sexual signals more divergent than ecological traits in closely related taxa? Using traits of known function in closely related populations, we show that traits predictive of reproductive performance are, indeed, more divergent and more sexually dimorphic than traits related to ecological adaptation.

Original languageEnglish
Pages (from-to)426-439
Number of pages14
JournalCurrent Zoology
Volume58
Issue number3
StatePublished - Dec 1 2012

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cumulative distribution
population size
sexual selection
population genetics
reproductive performance
sampling
genetic variation

Keywords

  • Effect size
  • Phenotype divergence
  • Sexual dimorphism
  • Sexual selection
  • Speciation

ASJC Scopus subject areas

  • Animal Science and Zoology

Cite this

Safran, R. J., Flaxman, S. M., Kopp, M., Irwin, D. E., Briggs, D., Evans, M. R., ... Uy, J. A. (2012). A robust new metric of phenotypic distance to estimate and compare multiple trait differences among populations. Current Zoology, 58(3), 426-439.

A robust new metric of phenotypic distance to estimate and compare multiple trait differences among populations. / Safran, Rebecca J.; Flaxman, Samuel M.; Kopp, Michael; Irwin, Darren E.; Briggs, Derek; Evans, Matthew R.; Funk, W. Chris; Gray, David A.; Hebets, Eileen A.; Seddon, Nathalie; Scordato, Elizabeth; Symes, Laurel B.; Tobias, Joseph A.; Toews, David P L; Uy, J. Albert.

In: Current Zoology, Vol. 58, No. 3, 01.12.2012, p. 426-439.

Research output: Contribution to journalArticle

Safran, RJ, Flaxman, SM, Kopp, M, Irwin, DE, Briggs, D, Evans, MR, Funk, WC, Gray, DA, Hebets, EA, Seddon, N, Scordato, E, Symes, LB, Tobias, JA, Toews, DPL & Uy, JA 2012, 'A robust new metric of phenotypic distance to estimate and compare multiple trait differences among populations', Current Zoology, vol. 58, no. 3, pp. 426-439.
Safran RJ, Flaxman SM, Kopp M, Irwin DE, Briggs D, Evans MR et al. A robust new metric of phenotypic distance to estimate and compare multiple trait differences among populations. Current Zoology. 2012 Dec 1;58(3):426-439.
Safran, Rebecca J. ; Flaxman, Samuel M. ; Kopp, Michael ; Irwin, Darren E. ; Briggs, Derek ; Evans, Matthew R. ; Funk, W. Chris ; Gray, David A. ; Hebets, Eileen A. ; Seddon, Nathalie ; Scordato, Elizabeth ; Symes, Laurel B. ; Tobias, Joseph A. ; Toews, David P L ; Uy, J. Albert. / A robust new metric of phenotypic distance to estimate and compare multiple trait differences among populations. In: Current Zoology. 2012 ; Vol. 58, No. 3. pp. 426-439.
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