When cladistic data sets include taxa with abundant missing entries, parsimony analysis may yield multiple equally optimal trees and necessitate the use of consensus methods to summarize relationships that are common to the multiple trees. Determination of those relationships that are common to the equally parsimonious trees and are thus unambiguously supported by the parsimonious interpretation of the data may not be possible using consensus methods that are widely employed by systematists. Thus, missing data may have an obfuscatory effect upon phylogenetic relationships. This problem can be ameliorated or overcome by adopting a strategy of safe taxonomic reduction. In this approach, taxa that can have no effect upon the relationships inferred for other taxa but that may increase the numbers of equally most-parsimonious trees are identified. Eliminating such taxa through the application of a series of safe deletion rules may reduce the number of equally most-parsimonious trees and thereby facilitate the consensus representation of unambiguous relationships supported by the data. The methods are illustrated by reanalysis of cladistic data for the Saurischia.
Systematic Biology is the bimonthly journal of the Society of Systematic Biologists. Papers for the journal are original contributions to the theory, principles, and methods of systematics as well as phylogeny, evolution, morphology, biogeography, paleontology, genetics, and the classification of all living things. A Points of View section offers a forum for discussion, while book reviews and announcements of general interest are also featured.
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Systematic Biology
© 1995 Oxford University Press
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