polytomy


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polytomy

(pə-lĭt′ə-mē)
n.
In a cladogram, a point from which two or more new branches diverge, representing either of two cases:
a. A multiple speciation event in which two or more species diverge from the same ancestor. Also called hard polytomy.
b. A speciation event in which two or more species are presumed to descend from the same ancestor, but the order of speciation is unknown. Also called soft polytomy.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
References in periodicals archive ?
Phylogenetically, Novumbra is either sister to Esox (Lopez and others 2004) or in a polytomy with Esox and Umbra (Grande and others 2004).
Microtus maximowiczii clades I and II are placed in an unresolved polytomy in the cytb tree with M.
(2009a), Cladium is the first branch to diverge, but Sclerieae + Bisboeckelereae form a polytomy with the remainder of Cyperoideae; in Jung and Choi (2012), both clades form a polytomy with the remainder of the Cyperoideae (cf.
The resulting consensus tree obtained after removing the 13 unstable OTUs shows an unresolved Pliosaurus polytomy and a partially resolved monophyletic Brachaucheninae clade (Figure 8B).
Those authors found the Jacob's Well specimens to fall within a large Eurycea complex polytomy that includes salamanders from sites recognized to have E.
galloprovincialis-SH clustered into a large polytomy indicating considerable uncertainty in the relationship among these taxa.
There remains substantial disagreement as to which taxon (or group) is most closely related to Euneomyini; analyses that include only Cytb and IRBP sequence data tend to suggest that this tribe forms a group (in some cases, with strong Bayesian but poor bootstrap support) with Chinchillula, followed by a clade that includes Andinomys and Punomys (e.g., Salazar-Bravo et al., 2013; Pardinas et al., 2014) or as a clade within a polytomy that also includes Chinchillula and Reithrodon (see Carrizo and Catalano, in press).
The presence of the fragmentary taxon "G." phuwiangensis creates a polytomy between Sunosuchus, Eutretauranosuchus and "G." phuwiangensis.
The large geographic range of the A.I.12 subgroup and the phylogenetic pattern of a long branch leading to a polytomy with genetic homogeneity point to a possible adaptive advantage for this subgroup.