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ON OUTGROUPS.

Kevin C Nixon1, James M Carpenter2

  • 1Bailey Hortorium, Cornell University, Ithaca, New York 14853, U.S.A.

Cladistics : the International Journal of the Willi Hennig Society
|December 21, 2021
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Summary
This summary is machine-generated.

This study clarifies relationships among polarity, outgroups, and rooting in phylogenetic analysis. It recommends discarding outdated methods in favor of unconstrained, simultaneous analysis for robust evolutionary insights.

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Area of Science:

  • Phylogenetics and Evolutionary Biology
  • Computational Biology

Background:

  • Phylogenetic analysis relies on understanding relationships between polarity, outgroups, and rooting.
  • Existing methods like the "outgroup algorithm" and "outgroup substitution method" have limitations.
  • Lundberg rooting's consistency with cladistic parsimony is conditional.

Purpose of the Study:

  • To clarify the relationships among polarity, outgroups, and rooting in phylogenetic inference.
  • To evaluate and propose improvements to existing outgroup and rooting methodologies.
  • To provide a clear framework for applying these concepts in evolutionary studies.

Main Methods:

  • Clarification of theoretical relationships between key phylogenetic concepts.
  • Critique and rejection of specific relaxed parsimony methods.
  • Description of a revised outgroup method with textual explanation and a flowchart.
  • Analysis of the conditions under which Lundberg rooting aligns with cladistic parsimony.

Main Results:

  • The "outgroup algorithm" and "outgroup substitution method" are identified as irrelevant forms of relaxed parsimony.
  • Unconstrained, simultaneous analysis of all terminals is proposed as a superior alternative.
  • A revised outgroup method is presented for practical application.
  • Specific conditions for the consistency of Lundberg rooting with cladistic parsimony are detailed.

Conclusions:

  • Outdated "outgroup" methods should be abandoned in favor of more comprehensive analyses.
  • Unconstrained, simultaneous analysis offers a more reliable approach to phylogenetic reconstruction.
  • The revised outgroup method provides a practical tool for researchers.
  • Understanding the specific conditions for Lundberg rooting is crucial for its correct application.