Cited by 395Marine Invertebrate Physiology and EcologyProtist diversity and phylogenyGenomics and Phylogenetic Studies

The DOI matches its Crossref record; 42 of the 46 references it cites were found in a registry or an index; none of the 15 sources its claims cite is checked for support yet.

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

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Medina, Mónica, Collins, Allen G., Silberman, Jeffrey D., Sogin, Mitchell L.·2001·Proceedings of the National Academy of Sciences

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 a monophyletic 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.

Overview

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TL;DR

Complete LSU and SSU rRNA sequences for 23 taxa were used to test competing hypotheses of basal metazoan phylogeny. The data strongly reject Hexactinellida as basal within a monophyletic Porifera or as sister to all other animals, support a Silicea clade of Hexactinellida plus Demospongia, and reject Ctenophora as closer to Bilateria than Cnidaria in SSU and combined analyses.

Key findings

  • LSU, SSU, and combined data reject two sponge hypotheses: Porifera monophyletic with Hexactinellida basal (KH P = 0.021, 0.002, 0.000 for SSU, LSU, combined) and Hexactinellida sister to all other Metazoans (KH P = 0.028, 0.005, 0.000). Instead, Hexactinellida and Demospongia form a well-supported Silicea clade (ML bootstraps 95 and 100); whether Calcarea is closer to Silicea or to nonsponge animals remains unclear.
  • SSU and combined data reject Bilateria being more closely related to Ctenophora than to Cnidaria (KH P = 0.022 and 0.033), whereas LSU alone does not (P = 1.000).
  • LSU and SSU agree in supporting monophyly of Bilateria, Cnidaria, Ctenophora, and Metazoa; ML bootstraps were 100 except Cnidaria (77 and 62) and Metazoa (63 and 63), and combined data raised Cnidaria and Metazoa support to 98 and 99.
  • LSU and combined data reject Hydrozoa as sister to other cnidarians (KH P = 0.004 and 0.016; SH LSU P = 0.036), and SSU data reject Choanoflagellida as sister group to Metazoa (KH P = 0.049).

Methods

  • Compiled complete LSU and SSU rRNA sequences for 23 taxa; 17 LSU and 3 SSU sequences were new. LSU was sequenced from mainly nonbilaterian animals (one mesomycetozoan, two choanoflagellates, four sponges, five cnidarians, three ctenophores, two bilaterians); SSU from three cnidarians; three fungi served as outgroup.
  • Final alignment contained 4,003 characters (SSU 1,595; LSU 2,408), with 1,779 variable and 1,216 parsimony-informative sites combined. Secondary structure was encoded and ambiguous regions excluded; model selection used nested likelihood ratio tests in modeltest, and analyses used paup*.
  • Constrained ML searches for a priori hypotheses were compared with Kishino–Hasegawa tests; unconstrained ML and MP searches (2:1 transversion:transition weighting) were compared with Shimodaira–Hasegawa tests; support estimated with 100 ML and 1,000 MP bootstrap pseudoreplicates and Bremer indices; analyses repeated excluding D. tigrina.

Limitations

  • Stated: taxon sampling is relatively limited, particularly outside the fungal/animal divergence, and may be inadequate to resolve the closest relatives of animals; bilaterian taxa have the longest branches, so the position of Bilateria in any topology may be artifactual.
  • Stated: SSU rRNA data have limitations including nucleotide compositional bias, among-site rate variation, and heterogeneous rates across lineages; LSU may share similar limitations because of similar functional constraints and genetic linkage.
  • Evident from the text: the SH test did not yield many significant P-values, and SSU data did not refute any hypotheses under SH; LSU alone failed to reject the Ctenophora-sister-to-Bilateria hypothesis.

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Integrity signals

Registry

Crossref · 10.1073/pnas.171316998

Cites

42 of 42 references verified0 citation errors · 0 not checkable

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  • It may state two separate claims as one. 10
  • Probably not a substantial claim. 6
14 of 14
  • The authors state this as an assumption.

    Comparative zoology is predicated on the assumption of a phylogenetic history.

    “Comparative zoology is predicated on the assumption of a phylogenetic history.”
  • The paper relies on this without support.

    The best measure of the validity of any hypothesis is provided by the accord or incongruence of alternative lines of evidence.

    “Nevertheless, the best measure of the validity of any hypothesis is provided by the accord or incongruence of alternative lines of evidence.”
  • The paper relies on this without support.

    Determining orthologs is not problematic for ribosomal genes because of the mechanisms of concerted evolution.

    “Unlike for some protein coding genes, determining orthologs is not problematic for ribosomal genes because of the mechanisms of concerted evolution.”
  • The paper relies on this without support.

    The best available model of sequence evolution selected by likelihood ratio tests is adequate for phylogenetic analysis.

    “We performed nested likelihood ratio tests (LRT) by using modeltest version 3.0 (30) to determine the best available model of sequence evolution for the SSU, LSU, and combined data, as well as the stem and loop regions of each gene.”
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Citations

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4 of the 46 references couldn’t be matched to a known paper.

Research works printed but not linked: 7

  1. A G Collins, J H Lipps, J W Valentine Paleobiology 26, 47–55 (2000). · DOI
  2. A G Rodrigo, P R Bergquist, P L Bergquist, R A Reeves Sponges in Time and Space, eds R W M van Soest, T M G van Kempen, J-C Braekman (Balkema, Rotterdam, The Netherlands), pp. 47–54 (1994).
  3. P De Rijk, Y Van De Peer, I Van Den Broeck, R De Wachter J Mol Evol 41, 366–375 (1995).
  4. D L Swofford paup* (Sinauer, Sunderland, MA, 2000).
  5. H Böger Meyniana 40, 67–90 (1988).
  6. J Reitner, D Mehl Verh Naturwiss Ver Hamburg 36, 5–32 (1996).
  7. L H Hyman The Invertebrates (McGraw–Hill, New York), pp. 726 (1940).

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Metadata

Authors
Medina, M., Collins, A. G., Silberman, J. D., & Sogin, M. L.
Affiliations
Marine Biological Laboratory (US)
Venue
Proceedings of the National Academy of Sciences
Published
2001-08-14
Volume
98
Issue
17
Pages
9707-9712
ISSN
  • 0027-8424 (ISSN-L)
  • 1091-6490
OpenAlex
W2028169893
Cited by
395
References
46
Citations by year
2026: 5 · 2025: 7 · 2024: 5 · 2023: 4 · 2022: 2 · 2021: 11 · 2020: 5 · 2019: 4 · 2018: 5 · 2017: 4 · 2016: 10 · 2015: 7 · 2014: 9 · 2013: 10 · 2012: 16
FWCI
23.98
Type
journal article
Language
en
Open access
Locations
  • Proceedings of the National Academy of Sciences (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • Smithsonian Digital Repository (Smithsonian Institution) (submittedVersion)
Funders
  • National Science Foundation (9814845)
  • National Aeronautics and Space Administration
  • Florida International University
  • National Institutes of Health (5r01gm032964-17, GM32964)
  • National Institute of General Medical Sciences (GM32964)
Topics
  • Life Sciences › Agricultural and Biological Sciences › Animal Science and Zoology › Marine Invertebrate Physiology and Ecology
  • Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Protist diversity and phylogeny
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Genomics and Phylogenetic Studies
Keywords
sponge phylogeny, Hexactinellida, Demospongiae, Silicea, calcareous sponges, sponges, Bilateria, Ctenophora, Cnidaria, monophyly, large subunit rRNA, small subunit rRNA, phylogenetic incongruence
MeSH terms
Animals, Animal Population Groups, Aplysia, Cnidaria, Echinodermata, Fungi, Models, Biological, Molecular Sequence Data, Phylogeny, Platyhelminths, Porifera, RNA, Fungal, RNA, Ribosomal, Sequence Homology, Nucleic Acid, Species Specificity, Urochordata, Xenopus laevis, Polymerase Chain Reaction, Sequence Alignment, Sequence Analysis, RNA, Evolution, Molecular

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