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Systematics Section / ASPT

Kirchoff, Bruce K. [1].

Representing Structural Homologies for use in Phylogenetic Analyses.

This paper presents a new method of conceptualizing cladistic characters as part of an ongoing effort to devise an operational definition of character and characters state. Character-state-trees are hierarchical clusters of traits based on primary homology assessments. They differ from the character-state trees in PAUP* in that they do not encode transformation series. They can be thought of as cladograms of traits (character-cladograms). The use of character-state-trees to represent primary homology has several advantages. First, it allows one to look at the process of character state construction as a grouping activity, and to apply insights from cognitive psychology to improve performance in the activity. Second, it allows the specification of relationships between character states without implying that one state transforms into another. This is in better accord with evolutionary theory, which recognizes the individual as the unit of evolutionary change, not the character. Third, treating character states as clusters of traits allows the inclusion of more data than would be possible with conventional character states. Conventional character states normally possess from two five mutually exclusive states. Character-state-trees can represent hierarchical relationships among traits, thereby increasing the information content of each character. The highest level of the hierarchy is the character itself, while the nested sets of partitions are the character states. According to this perspective, character states arise when homologous traits are placed into subcategories to create a (potentially) nested series of primary homologies. These clusters are equivalent to monophyletic groups, and provide an initial assessment of cladistic relationships among taxa. They can be coded for analysis using step-matrices, thus avoiding many of the problems with alternative character state codings that have been described in the literature. Because the hierarchy is created by an overt comparison among traits, problems with the application of verbal labels are also avoided.


Related Links:
Character Description in Systematics - A short background paper


1 - University of North Carolina at Greensboro, Department of Biology, P.O. Box 26170, Greensboro, North Carolina, 27402-6170, U.S.A.

Keywords:
character coding
Evolution
morphology
phylogenetics
phylogeny
characters
character state
homology
cladogram
character-state-trees.

Presentation Type: Paper
Session: 45-4
Location: Cottonwood B (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 9:00 AM
Abstract ID:40


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