Polytomies, the Power of Phylogenetic Inference, and the Stochastic Nature of Molecular Evolution: a Comment on Walsh et al. (1999)

Evolution, Vol. 55, pp. 1261­1263

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Polytomies, the Power of Phylogenetic Inference, and the Stochastic Nature of Molecular Evolution: a Comment on Walsh et al. (1999)

Edward L. Braun* and Rebecca T. Kimball

Departments of Plant Biology (E.L.B.) and Evolution, Ecology and Organismal Biology (R.T.K.), The Ohio State University, Columbus, Ohio 43210
E.L.B. and R.T.K. are currently in the Department of Zoology at the University of Florida.

Description of Paper, published as a Brief Communication in Evolution

The frequent recovery of polytomies (multifurcating rather than bifurcating relationships) in phylogenetic analyses has prompted interest in the biological nature of these inferred polytomies. Polytomies may reflect the inability to resolve bifurcating relationships (“soft” polytomies) or they may represent multiple simultaneous speciation events (“hard” polytomies; see Hoelzer and Melnick 1994 for additional discussion). Walsh et al. (1999) recently suggested that power analysis might provide an excellent framework for examining the nature of polytomies. We found this approach to be an innovative an interesting way to examine the question, but we also proposed a more direct way to examine the power of phylogenetic analyses to examine the null hypothesis of a polytomy in this brief communication. Walsh and Friesen (2001) agreed that our general approach was sound, but pointed out that the worked example in our comment required a larger power (had reduced type II error) than those typically used by convention.

polytomy

E.L.B. was supported by a United States Department of Agriculture fellowship (1999-01582) and R.T.K. was supported by a National Science Foundation grant to D. J. Crawford

* Corresponding author

References for the description of this paper:

  1. Hoelzer, GA & DJ Melnick. 1994. Patterns of speciation and limits to phylogenetic resolution. Trends in Ecology and Evolution 9:104­107.
  2. Walsh, HE & VL Friesen. 2001. Power and stochasticity in the resolution of soft polytomies: a reply to Braun et al. Evolution 55, No. 6:1264­1266.
  3. Walsh, HE, MG Kidd, T Moum & VL Friesen. 1999. Polytomies and the power of phylogenetic inference. Evolution 53:932­937.