Groundplans and exemplars: Paths to the tree of life

Yeates D.K. (1995) Groundplans and exemplars: Paths to the tree of life. Cladistics, 11 4: 343-357. doi:10.1016/0748-3007(95)90020-9


Author Yeates D.K.
Title Groundplans and exemplars: Paths to the tree of life
Journal name Cladistics   Check publisher's open access policy
ISSN 1096-0031
Publication date 1995-01-01
Sub-type Article (original research)
DOI 10.1016/0748-3007(95)90020-9
Open Access Status Not yet assessed
Volume 11
Issue 4
Start page 343
End page 357
Total pages 15
Subject 1105 Dentistry
Abstract During cladistic analysis of a diverse higher taxon it is impractical to code every species as a separate terminal. In such cases, workers proceed in one of two distinct ways: (1) examine a number of member species in order to deduce groundplan character states of the higher group before the analysis is begun, here called the intuitive method, or (2), code a number of real species belonging to the group as terminals in the analysis, called the exemplar method. Both methods have the same aim, to estimate the groundplan of the higher taxon concerned. Both groundplan estimation methods will lead to identical results when the character in question has the same state in all members of the terminal group, however when the character has two or more states, the two methods may give different results. The precise methods employed in the intuitive approach have not been articulated in the literature, but possible techniques may result in non-parsimonious ancestral state assignments, even in simple cases. Groundplan estimation in the exemplar method is an extension of parsimony. The exemplar method allows groundplan state/s at internal nodes to be calculated during tree search. In many cases the exemplar method assigns a number of possible states to the groundplan, and the state assignment is therefore equivocal. This is not a deficiency of the method but reflects the notion that the parsimony criterion alone cannot always distinguish a single state present in a hypothetical ancestor. The optimal choice of exemplars required to estimate the groundplan most efficiently is discussed under a simple and common hypothesis of character transformation. For complex character distributions up to three exemplars may be required, each from a separate lineage of the group close to its hypothetical common ancestral node.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: Scopus Import - Archived
 
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Created: Tue, 14 Jun 2016, 11:01:02 EST by System User