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Title: Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA

Abstract

We studied the evolutionary relationships among basal metazoan lineages by using complete large subunit (LSU) and small subunit (SSU) ribosomal RNA sequences for 23 taxa. After identifying competing hypotheses, we performed maximum likelihood searches for trees conforming to each hypothesis. Kishino-Hasegawa tests were used to determine whether the data (LSU, SSU, and combined) reject any of the competing hypotheses. We also conducted unconstrained tree searches, compared the resulting topologies, and calculated bootstrap indices. Shimodaira-Hasegawa tests were applied to determine whether the data reject any of the topologies resulting from the constrained and unconstrained tree searches. LSU, SSU, and the combined data strongly contradict two assertions pertaining to sponge phylogeny. Hexactinellid sponges are not likely to be the basal lineage of amonophyletic Porifera or the sister group to all other animals. Instead, Hexactinellida and Demospongia form a well-supported clade of siliceous sponges, Silicea. It remains unclear, on the basis of these data alone, whether the calcarean sponges are more closely related to Silicea or to nonsponge animals. The SSU and combined data reject the hypothesis that Bilateria is more closely related to Ctenophora than it is to Cnidaria, whereas LSU data alone do not refute either hypothesis. LSU and SSU datamore » agree in supporting the monophyly of Bilateria, Cnidaria, Ctenophora, and Metazoa. LSU sequence data reveal phylogenetic structure in a data set with limited taxon sampling. Continued accumulation of LSU sequences should increase our understanding of animal phylogeny.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Director, Office of Science. Office of Biological and Environmental Research. Life Sciences Division (US)
OSTI Identifier:
796014
Report Number(s):
LBNL-50245
R&D Project: LWCVMD; TRN: US200212%%323
DOE Contract Number:  
AC03-76SF00098
Resource Type:
Journal Article
Journal Name:
Proceedings of the National Academy of Sciences USA
Additional Journal Information:
Journal Volume: 98; Journal Issue: 17; Other Information: Journal Publication Date: Aug. 14, 2001; PBD: 21 Jun 2001
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; ANIMALS; CNIDARIA; HYPOTHESIS; RIBOSOMAL RNA; SAMPLING; TREES; PHYLOGENY OF METAZOA

Citation Formats

Medina, Monica, Collins, Allen G., Silberman, Jeffrey, and Sogin, Mitchell L. Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA. United States: N. p., 2001. Web. doi:10.1073/pnas.171316998.
Medina, Monica, Collins, Allen G., Silberman, Jeffrey, & Sogin, Mitchell L. Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA. United States. doi:10.1073/pnas.171316998.
Medina, Monica, Collins, Allen G., Silberman, Jeffrey, and Sogin, Mitchell L. Thu . "Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA". United States. doi:10.1073/pnas.171316998.
@article{osti_796014,
title = {Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA},
author = {Medina, Monica and Collins, Allen G. and Silberman, Jeffrey and Sogin, Mitchell L.},
abstractNote = {We studied the evolutionary relationships among basal metazoan lineages by using complete large subunit (LSU) and small subunit (SSU) ribosomal RNA sequences for 23 taxa. After identifying competing hypotheses, we performed maximum likelihood searches for trees conforming to each hypothesis. Kishino-Hasegawa tests were used to determine whether the data (LSU, SSU, and combined) reject any of the competing hypotheses. We also conducted unconstrained tree searches, compared the resulting topologies, and calculated bootstrap indices. Shimodaira-Hasegawa tests were applied to determine whether the data reject any of the topologies resulting from the constrained and unconstrained tree searches. LSU, SSU, and the combined data strongly contradict two assertions pertaining to sponge phylogeny. Hexactinellid sponges are not likely to be the basal lineage of amonophyletic Porifera or the sister group to all other animals. Instead, Hexactinellida and Demospongia form a well-supported clade of siliceous sponges, Silicea. It remains unclear, on the basis of these data alone, whether the calcarean sponges are more closely related to Silicea or to nonsponge animals. The SSU and combined data reject the hypothesis that Bilateria is more closely related to Ctenophora than it is to Cnidaria, whereas LSU data alone do not refute either hypothesis. LSU and SSU data agree in supporting the monophyly of Bilateria, Cnidaria, Ctenophora, and Metazoa. LSU sequence data reveal phylogenetic structure in a data set with limited taxon sampling. Continued accumulation of LSU sequences should increase our understanding of animal phylogeny.},
doi = {10.1073/pnas.171316998},
journal = {Proceedings of the National Academy of Sciences USA},
number = 17,
volume = 98,
place = {United States},
year = {2001},
month = {6}
}