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Impact of outgroup inclusion on estimates by parsimony of undirected branching of ingroup phylogenetic lines
Author(s) -
Baum Bernard R.,
Estabrook George F.
Publication year - 1996
Publication title -
taxon
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 81
eISSN - 1996-8175
pISSN - 0040-0262
DOI - 10.2307/1224664
Subject(s) - outgroup , ingroups and outgroups , monophyly , biology , phylogenetic tree , phyletic gradualism , maximum parsimony , taxon , clade , paleontology , psychology , genetics , social psychology , gene
Summary Baum, B. R. & Estabrook, G. F: Impact of outgroup inclusion on estimates by parsimony of undirected branching of ingroup phylogenetic lines. – Taxon 45: 243‐257. 1996. – ISSN 0040‐0262. Some of the effects of including outgroup taxa on the branching pattern of the ingroup taxa are revealed by an artificial example, and illustrated with a more complex natural example involving the grass genus Kengyilia. To reduce the total number of changes required by a branching pattern, parsimony may prefer to reduce the number of changes on temporally long phyletic lines to more distant outgroups while increasing changes on temporally short phyletic lines within the ingroup. This may have the effect of bringing the ancestors that define monophyletic groups within the ingroup down to the phyletic line to the outgroup, which converts them to paraphyletic groups. Thus the inclusion of outgroup taxa during parsimony may alter the branching pattern of the ingroup to destroy distinct monophyletic groups and instead create nested series of monophyletic groups, reminiscent of the chaining properties of some phenetic methods. If similarities between ingroup and outgroup are true homoplasies, then removal of these homoplasies will produce error. However, parsimony estimates of ingroup may produce bogus monophyletic groups because no account has been made of the ingroup's most recent common ancestor.